Soil nitrogen(N)cycling enzyme activity serves as a crucial indicator for characterizing soil fertility and N transformation.To investigate the effects of long-term application of fertilizers on the soil enzyme activities correlated with N cycling in rhizosphere soil of double-cropping rice fields in southern China,our project was based on a continue 37-year fertilization localization field experiment,including four fertilization treatments:without fertilizer as a control(CK),single fertilizer(MF),rice straw residue and mineral fertilizer(RF),and 30% organic manure and 70% mineral fertilizer(OM).The activities of N cycling enzymes in the rhizosphere soil were measured,and their correlation with soil chemical properties was analyzed.The results were as follows:compared to MF and CK treatments,OM and RF treatments significantly increased the contents of total N(TN),organic carbon(SOC),ammonium N($\mathrm{NH}_{4}^{+}-\mathrm{N}$),nitrate N($\mathrm{NO}_{3}^{-}-\mathrm{N}$)and microbial biomass N(SMBN)in rhizosphere soil,and also increased rice yield.The urease(Ure)and nitrite reductase(NiR)activities of rhizosphere soil in OM and RF treatments were significantly higher than those in MF and CK treatments.The RF treatment significantly increased rhizosphere soil hydroxylamine reductase(HyR)activities compared to the other three treatments,by 21.7%,13.0%,and 8.7%,respectively.This finding shown that OM treatment significantly increased protease(Pro),nitrogenase(Nit),nitrate reductase(NR)and nitrous oxide reductase(Nos)in rhizosphere soil compared to RF,MF and CK treatments.In comparison to MF treatment,OM treatments increased Pro,Nit,NR and Nos activities in rhizosphere soil by 20.0%,26.1%,426.1% and 26.7%,respectively.Nonetheless,the activity of nitric oxide reductase(Nor)on rhizosphere soil was considerably higher in the CK treatment than in MF,RF and OM treatments.Pearson correlation analysis revealed a substantial positive correlation between soil NR,NiR,Nit,Nos,Ure,Pro and soil TN,SOC,$\mathrm{NH}_{4}^{+}-\mathrm{N}$,$\mathrm{NO}_{3}^{-}-\mathrm{N}$,SMBN as well as rice yield.Soil Nor activity was observed to have a significantly negative connection with soil TN,SOC,$\mathrm{NH}_{4}^{+}-\mathrm{N}$,$\mathrm{NO}_{3}^{-}-\mathrm{N}$,SMBN and rice yield.The findings presented above showed that soil chemical properties and yield were substantially related to rhizosphere soil N cycling enzyme activities.Redundancy analysis(RDA)showed that the first order axis could explain 93.34% of the enzyme activity in rhizosphere soil and soil $\mathrm{NO}_{3}^{-}-\mathrm{N}$,TN and SOC contents were the key factors affecting the pattern of rhizosphere soil enzyme activities.Therefore,the long-term application of organic materials such as organic manure and rice straw can enhance soil chemical and biological characteristics,stimulate soil N cycling enzyme activities,and effectively fertilize paddy soils by partially replacing chemical fertilizers.

In order to provide production advice of high-quality upper tobacco leaves,field experiment was carried out to elucidate the effects of nitrogen application on the growth,development,carbon and nitrogen metabolism of upper leaves of different tobacco varieties.Three treatments,37.5(LN),75.0(MN)and 112.5 kg/ha nitrogen application rate(HN)were conducted with NC89 and Yunyan 87 as the test varieties.The effects of different treatments on the agronomic traits,photosynthetic characteristics,leaf tissue structure,key enzymes activity of carbon and nitrogen metabolism,and chemical composition of the upper leaves of were studied.The results showed that the leaf length,leaf width,leaf area,and leaf dry mass of the upper leaves of both varieties were significantly improved with the increased of nitrogen application rates.At 115 days after transplanting(DAT),the leaf area of NC89 and Yunyan 87 of HN were significantly increased by 63.10% and 68.43% compared to LN,respectively.Increasing nitrogen rate improved the leaf chlorophyll content of NC89,the leaf chlorophyll content of HN was 6.67%—37.50% higher than that of LN,respectively.The leaf net photosynthetic rate was notably improved by increasing nitrogen rate of Yunyan 87,especially at 70 DAT and 80 DAT.The leaf palisade tissue,leaf spongy tissue,and leaf thickness were markedly promoted with the increased nitrogen application rate on 85—115 DAT.The palisade tissue and spongy tissue thickness of LN and MN were almost stable from 95 to 115 DAT,but HN improved by 9.82%—14.08% and 10.72%—13.72% respectively.The leaf carbon content and leaf carbon and nitrogen ratio of both varieties were significantly decreased by reduced nitrogen rate,while leaf nitrogen content significantly increased.The activities of invertase,sucrose phosphate synthase,sucrose synthase,and glutamate synthase of both varieties were increased with the increased nitrogen application rate.HN decreased the amylase activity of Yunyan 87,but increased that of NC89.At 115 DAT,the amylase activity of HN of Yunyan 87 was 27.53% lower than MN,while HN increased amylase activity by 33.86% and 21.74% compared to LN and MN of NC89,respectively.The activity of glutamine synthetase of Yunyan 87 significantly increased with the increased nitrogen application rate,while there was no significant difference among different treatments of NC89.The content of flue-cured tobacco leaf reducing sugar and total sugar were reduced,but the content of nicotine and total nitrogen were improved with increased nitrogen application rate.Under the same nitrogen application rate,the content of flue-cured tobacco leaf nicotine,total nitrogen,and potassium of Yunyan 87 were higher than NC89,while the content of reducing sugar,content of total sugar(except LN),sugar and nicotine ratio,and nitrogen and nicotine ratio were lower than NC89.The effect of nitrogen application rate on upper leaves of tobacco varieties is difference.Increasing nitrogen application rate could promote the growth,development and carbon metabolism,reduce sugar and nicotine ratio and nitrogen and nicotine ratio,and improve the coordination of chemical components of NC89.However,increasing nitrogen application rate could lead to excessive nitrogen metabolism,delay the transformation from nitrogen metabolism to carbon accumulation metabolism,and cause late maturity of Yunyan 87.

To clarify the regulatory effect of nitrogen(N)fertilizer reduction and postponing on the productivity of wheat-maize double cropping system in Huang-Huai-Hai Plain.The annual N fertilizer experiment of summer maize and winter wheat was established of four N application systems:annual N fertilizer application 400 kg/ha of traditional farmer treatment(F₄₀₀),10% reduction of annual N fertilizer(FN),20% reduction of annual N fertilizer(FH),and 30% reduction of annual N fertilizer(FL)from 2020 to 2023 at Jiyang Experimental Base of the Shandong Academy of Agricultural Sciences in Jinan.The grain yield,aboveground N accumulation characteristics,N use efficiency,and the nitrate residue after harvest in the 0—200 cm soil layer of wheat-maize double cropping system were tested,in order to provide the theoretical basis for further optimization of N fertilizer management in Huang-Huai-Hai Plain.The results indicated that N fertilizer postponing was optimized the grain yield of summer maize and winter wheat under the condition of N reduction,and the averaged across the three years,FL significantly increased by 9.2%—18.1%,13.5%—20.5%,and 11.1%—19.1%,respectively,compared with F₄₀₀ and FN.N fertilizer postponing improved the N accumulation rate,and promoted aboveground N accumulation at wheat-maize different growth stages,and the averaged across the three years,FL significantly increased plant N accumulation by 5.7%—12.3% and 5.0%—12.8% under silking and maturity,respectively,compared with F₄₀₀,FN,and FH,as well as 8.2%—17.2% in grain N accumulation.For winter wheat,FL and FH treatments were significantly higher than F₄₀₀ and FN at jointing,anthesis,and maturity,and the averaged across the three years,FL and FH significantly increased by 23.4%—28.1%,20.7%—26.3%,and 12.6%—20.8%,respectively,compared with F₄₀₀,FN and FH,at the same time the grain N accumulation under FL significantly increased by 16.4%,15.0% and 5.8%,respectively,compared with F₄₀₀ and FN.N fertilizer postponing optimized the N use efficiency of wheat-maize double crop system,the averaged across the three years,FL significantly increased N uptake efficiency by 4.8%—57.7% and 32.0%—72.4% of summer maize and winter wheat,respectively,compared with F₄₀₀,FN,and FH;and FL significantly increased N partial factor productivity by 68.8% and 40.4% in summer maize,respectively,compared with F₄₀₀ and FN,as well as by 38.4%—71.8% in winter wheat compared with F₄₀₀,FN,and FH.At harvest of summer maize and winter wheat,the soil nitrate residue was mainly enrichment in the 0—40 cm soil layer under four N application systems,the averaged across the three years,accounted for 40.0%,38.9%,44.9%,42.5% and 37.3%,36.9%,46.7%,38.3% of the 0—200 cm soil layer,respectively.In addition,the obvious accumulated effects in 0—200 cm soil layer nitrate residue under F₄₀₀ and FN treatments at harvest of summer maize and winter wheat,but there was the relative balance was achieved under FL and FH treatments.In conclusion,a 30% reduction of annual N fertilizer by N fertilizer postponing could optimize plant N accumulation characteristics and realized synergistic improve grain yield and N use efficiency.Therefore,FL treatment was an optimal N application system for realizing the collaborative target of high-yield,high-efficiency,and environment-friendly of wheat-maize double cropping system in Huang-Huai-Hai Plain.

To explore the impact of organic fertilizer on the physiological growth of flax and the rhizosphere bacterial communities,and to investigate green high-yield cultivation techniques for flax in dryland,a field experiment was conducted using Baxuan No.3 as the material.The study examined the effects of four different fertilization treatments(T0:no application; T1:low quantity of cow manure; T2:medium cow manure; T3:high quantity of cow manure)on the physiological growth changes,nitrogen utilization,dry matter accumulation,and the diversity,community composition,co-occurrence networks,and metabolic pathways of the rhizosphere bacteria of flax,as well as discussing the environmental factors driving the differences in bacterial communities.The results showed that the T3 treatment resulted in higher flax production. Compared to the control, this fertilization condition also had the highest indicators for plant height, capsule fruit number per plant, thousand-grain weight, and nitrogen use efficiency, which form the physiological basis for stable yield following the application of organic fertilizer.The application of organic fertilizer significantly affected the diversity and richness of the rhizosphere soil bacteria of flax,and there were significant differences in the structure of the rhizosphere bacterial community.The population structure of the rhizosphere bacteria of flax was influenced by organic matter,total nitrogen,and available phosphorus.The dominant flora in the rhizosphere of flax was the same across different treatments,but the relative abundance of each dominant flora varied significantly.The rhizosphere of flax was dominated by the phyla Proteobacteria,Actinobacteria,Acidobacteria,Chloroflexi,and Bacteroidetes.The relative abundance of Proteobacteria and Actinobacteria increased with the increase of organic fertilizer treatments,while that of Acidobacteria decreased with the increase of organic fertilizer treatments.WGCNA analysis identified 15 co-expression modules,with the Red and Pink modules showing a significant positive correlation with organic matter content.The application of organic fertilizer increased the complexity of the bacterial network,and seven key OTUs were identified through combined WGCNA analysis.In conclusion,the application of organic fertilizer promoted the growth of flax and altered the structure and network complexity of the bacterial community in the rhizosphere soil of flax.

In order to explore a good fertilization model to improve the fertility of yellow-cinnamon soil in Southern Henan,the characteristics of stable and high yield of wheat-maize rotation system and its relationship with soil nutrients under different fertilization treatments on yellow-cinnamon soil were studied.Based on the long-term experiment since 2012,four treatments were set up:no fertilizer(CK),chemical fertilizer(NPK),chemical fertilizer combined with manure(NPKM)and chemical fertilizer combined with straw(NPKS).Plants and soil samples were collected at maturity stage to determine crop yield and soil organic carbon,alkaline nitrogen,available phosphorus and available potassium.The results showed that compared with CK treatment,the crop yield of each fertilization treatment was significantly increased,the yield of wheat was increased by 53.70%—64.50%,and the yield of maize was increased by 44.54%—58.31%.The yield of NPKM treatment was the highest(wheat 8 162.61 kg/ha,maize 8 836.33 kg/ha),and there was no significant difference between NPKS and NPKM treatments.The yield sustainability index(SYI)of NPKM treatment was the highest,and the SYI values of wheat season and maize season were 0.84 and 0.82,respectively.The crop yield and its SYI value both showed NPKM>NPKS>NPK>CK,indicating that chemical fertilizer combined with organic materials could significantly increase crop yield and its sustainability.At the same time,different fertilization treatments could improve soil nutrients to varying degrees,among which NPKM treatment had the most significant improvement effect.The relationship between crop yield and soil nutrients was analyzed.The relationship between crop yield and soil nutrients was analyzed.There was significantly positive correlation between crop yield and soil organic carbon(SOC),available nitrogen and available phosphorus contents,among which the correlation between crop yield and SOC was the most significant.With the increase of soil organic carbon content,the SYI value of crops increased first and then stabilized,and the inflection point was 15.15 g/kg.To sum up,the application of chemical fertilizer combined with manure can significantly increase crop yield and soil nutrients,and maintain high crop yield sustainability.It is a recommended fertilization model to achieve sustainable production of soil-crop system in yellow-cinnamon soil ecological zone.

The aim was to clarify the effects of different nitrogen application levels on soil organic nitrogen fractions and nitrogen use efficiency in maize fields in the central-western region of Inner Mongolia,so as to provide a reference for the scientific management of soil nitrogen and sustainable development of modern agriculture.Six nitrogen application levels were set up,N0(0 kg/ha),N8(120 kg/ha),N12(180 kg/ha),N16(240 kg/ha),N20(300 kg/ha),and N24(360 kg/ha).The dynamic changes with effects of nitrogen application on soil total nitrogen content,particulate organic nitrogen content,light fraction organic nitrogen content and heavy organic nitrogen content,as well as maize yield and nitrogen use efficiency were analyzed at different soil layers at pre-sowing and post-harvest.The results showed that soil total nitrogen,particulate organic nitrogen,light fraction organic nitrogen,and heavy fraction organic nitrogen content decreased with deepening of the soil layer at the same nitrogen application level;soil total nitrogen content at pre-sowing increased with the nitrogen application levels.Soil total nitrogen content in the N16,N20,and N24 treatments was significantly higher than that in the N0,N8,and N12 treatments at post-harvest.Soil particulate organic nitrogen content of N16 treatment was highest in the 0—10 cm,10—20 cm,and 20—40 cm soil layers at pre-sowing,with 0.14,0.13,and 0.09 g/kg,respectively.At post-harvest,N16 treatment had the highest content in the 10—20 cm,20—40 cm,and 40—60 cm soil layers,with 0.19,0.10,and 0.09 g/kg,respectively.The highest increase of soil light fraction organic nitrogen content of 37.27% was in the N16 treatment,and the highest increase of soil heavy fraction organic nitrogen content of 7.35% was in the N24 treatment,followed by the N16 treatment,at 6.84%.The N16 treatment had the highest maize biological yield of 31 443.50 kg/ha;the highest maize economic yield of 18 526.47 kg/ha;and the nitrogen use efficiency decreased with the increase in nitrogen fertilizer application levels,N16 treatment in the nitrogen harvest index was the highest, at 79.20%.In conclusion,the more suitable nitrogen fertilizer application level in the central-western region of Inner Mongolia should be maintained under 240 kg/ha,in order to achieve the best soil nitrogen management ang crop yield.

In order to investigate the effects of reactive oxygen species(ROS)on the growth and antioxidant system of sweetpotato under potassium deficiency stress,and further reveal the defense mechanism of ROS regulation in sweetpotato under potassium deficiency stress.This study selected two sweetpotato varieties,Xushu32(low potassium tolerant)and Ningzi 1(low potassium sensitive),as experimental materials.The experiment was conducted in an artificial climate chamber using hydroponic cultivation to ensure consistent environmental conditions.After pretreatment with exogenous H₂O₂ and diphenyl chloroiodate(DPI),ROS inhibitor,the sweetpotato seedlings were subjected to potassium deficiency treatment.The changes in relative H₂O₂ content,antioxidant gene expression levels,and enzyme activity indicators in sweetpotato roots at different time points after potassium deficiency treatment were measured.The morphological characteristics of sweetpotato were recorded to explore the effects of ROS signaling on the growth of sweetpotato seedlings under potassium deficiency stress.The results showed that under potassium deficiency treatment,the biomass of sweetpotato decreased and leaf color lightened.The relative concentration of ROS in sweetpotato seedling roots showed the highest fluorescence intensity on the 14th day.The expression levels of antioxidant-related genes in sweetpotato roots generally increased,with a more significant increase in expression levels after H₂O₂ pretreatment.Compared with-K treatment,both H₂O₂ and DPI pretreatment could enhance the activity of antioxidant enzymes in sweetpotato leaves,and different enzyme activities showed different trends within 21 days of potassium deficiency treatment.There were varietal differences in the effects of different treatments.The experimental results showed that H₂O₂ could act as a stress signaling molecule to increase the expression level of antioxidant genes and the enzymatic activities of APX,SOD and POD in sweetpotato seedlings,thus scavenging excess ROS and effectively alleviating the inhibition of growth of sweetpotato seedlings by potassium deficiency stress.And DPI could inhibit the production of endogenous H₂O₂,maintain the antioxidant enzyme activity,protect the ROS enzymatic scavenging system of sweetpotato seedlings and avoid oxidative damage to tissues.

Saline-alkali soils are an important reserve arable land resource in China,and are generally characterized by high inorganic salt content,lack of organic matter and low soil fertility,which seriously affects China's food security.Therefore,there is a need to improve the saline soil condition,enhance soil fertility,and provide a more reliable guarantee for China's food security.In China,straw is an important agricultural organic waste,the resource utilization of straw has become an important part of sustainable agricultural development.Among them,straw return to field has been widely promoted as a core measure.A large number of studies have shown that by returning straw to the field in a reasonable manner,the structure of soil can be effectively improved,the organic carbon content of soil can be increased,and the fertility of soil can be improved.At present,how straw resources can be efficiently utilized in saline-alkali soils so that the organic carbon of saline-alkuli soils can be improved is a major issue facing Chinese agriculture.Therefore,this paper summarizes the different ways and amounts of straw return to the field to investigate its effects on the organic carbon pool and components of saline-alkali soils.On this basis,the shortcomings of straw return technology are proposed and solutions are found.In practice,appropriate treatment measures are taken for further realizing the improvement of saline-alkali land by straw return to the field.In addition,conducting saline-alkali land research is not only an in-depth analysis of a specific soil environment,but also a complex systematic project involving the intersection of multiple disciplines.In this process,various factors,including but not limited to land management,hydrogeology,ecosystem,and agricultural economics,must be fully considered.Through such efforts,we will be able to gain a deeper understanding of the characteristics of saline-alkali soils and provide a scientific basis and technical support for the improvement and utilization of these valuable resources.

The shortage of fresh water resources is an important factor restricting the sustainable development of agriculture,and the adoption of saltwater irrigation with appropriate concentration is an effective way to make up for this shortage,but the continuous use of saltwater irrigation may increase the risk of soil secondary salinization.Therefore,salt leaching should be ensured when using saltwater irrigation.In order to accurately evaluate the long-term effects of saline irrigation on soil and the effect of increased application of organic fertilizer on salt leaching,this study relied on 10 consecutive years of dry treatment and 1,3,5 g/L saline water irrigation,respectively.Applying chemical fertilizer and increasing the application of organic fertilizer based on chemical fertilizer.By analyzing soil water content,electrical conductivity,pH,organic matter,total nitrogen,available phosphorus and total phosphorus contents per 20 cm of 0-200 cm soil profile,it was found that saline irrigation with different concentrations had no significant effect on surface soil electrical conductivity and other characteristics.The saline water irrigation treatment of 5 g/L increased the soil salt content below 0-20 cm and 120 cm under the application of organic fertilizer.In addition,compared with chemical fertilizer treatment,the addition of organic fertilizer treatment significantly increased the soil surface water content,organic matter,total nitrogen,available phosphorus and total phosphorus contents,and the indexes increased by 14.16%,38.27%,32.39%,44.25% and 9.56%.It can be seen that although the application of organic fertilizer increased the soil conductivity,the soil was still in a low salt environment,and the increase of organic fertilizer increased the content of soil nutrients(especially available phosphorus)more significantly.At the same time,due to rainfall and freshwater irrigation before winter wheat planting,saline water irrigations<5 g/L in this area will not cause salt accumulation in the surface soil.

In order to explore the production performance and soil improvement effect of sweet sorghum in saline-alkali land,Zhongketian 438 sweet sorghum was planted in Southern Xinjiang,and its yield was measured,in addition,0-10 cm,10-20 cm,20-30 cm soil layers were selected on saline-alkali land before planting and after harvesting of feed sweet sorghum varieties,and the effects of soil physical and chemical properties,soil ions and soil enzyme activities were measured and compared.The results showed that the total salinity,pH value and electrical conductivity of the soil decreased after the planting of sweet sorghum.Compared with before planting,the contents of Na⁺,K⁺,HCO₃^-,Cl^-and SO₄^2- and total potassium,total phosphorus,available phosphorus and available nitrogen decreased significantly,while the contents of Ca²⁺,Mg²⁺,total porosity,organic matter,total nitrogen and available potassium increased.The content of Mg²⁺ in soil cation was highest,and the content of SO₄^2- in anion was the higher than that of Cl^-.In soil enzyme activity,the activities of catalase,sucrase and alkaline phosphatase were not significantly different,but the urease activity was significantly different.Compared with before planting,the change of 10-20 cm soil layer in different soil layers was more obvious.The results of correlation analysis showed that there was a significant positive correlation between pH value and total salinity;there was a significant negative correlation between bulk density and pH,total salinity;and a significant positive correlation between sucrase and alkaline phosphatase.The above results showed that the saline-alkali soil in this area is a soil type dominated by Na₂SO₄,and the cultivation of feed sweet sorghum in the saline-alkali soil in this area could not only harvest high-yield forage grass,but also reduce some ions in the soil to improve soil physical and chemical properties.

In order to clarify the effects of different irrigation and fertilization combinations on soil nutrients in Bashang area of Zhangjiakou on the basis of adding soil conditioner.Two two-factor tests were set:irrigation frequency and fertilizer amount,irrigation frequency and irrigation amount.Factor one was different irrigation frequency:6 d(D6),8 d(D8)and 10 d(D10).The second factor was different fertilizer dosage:100% fertilizer(F100),conditioner+100% fertilizer(PF100),conditioner+85% fertilizer(PF85),conditioner+70% fertilizer(PF70).The three factors were different irrigation amounts:100% irrigation(W100),85% irrigation(W85),70% irrigation(W70),a total of 24 treatments.The effects of different irrigation and fertilization levels on soil water content and nutrients as well as the changes of nutrients in different soil layers were analyzed.The results showed that the average water content of soil with high frequency or medium frequency irrigation(D6 or D8)was the highest in 0-60 cm soil layer.Compared with medium frequency irrigation(D8)treatment,D6 treatment could significantly increase the soil organic matter content of 0-20 cm and the total nitrogen and available potassium content of 20-40 cm soil.Compared with conventional irrigation and fertilization(F100 and W100),PF100 and PW100 could significantly increase the average soil water content,total nitrogen,available phosphorus and available potassium content in 0-20 cm soil layer,and the average organic matter and nitrate nitrogen content in 20-40 cm soil layer.In addition to the soil conditioner,water reduction and weight loss can still significantly increase the surface soil nutrient content.PF85,PW85 or PF70,PW70 could significantly increase the average soil organic matter(14.4%-19.0%),total nitrogen(2.2%-11.2%),available phosphorus(22.2%-41.7%),available potassium(4.9%-42.8%)and the average soil nitrate nitrogen in 20-40 cm soil layer(20.8%-95.0%).The correlation analysis showed that soil water content was positively correlated with organic matter,total nitrogen and soil available potassium(R²=0.081,0.092 and 0.166)under high frequency irrigation and soil available phosphorus and available potassium(R²=0.114 and 0.153)under medium frequency irrigation.In conclusion,the combination of water and fertilizer with 100% fertilization and 70% irrigation+conditioner(PF100D6 and PW70D6)is the best to improve soil nutrients under high-frequency irrigation conditions.The results can provide a scientific basis for the optimal management of irrigation and fertilization in arid northern China and other areas with similar environment.

In order to explore the effects of combined application of amino acid fertilizer and urea on soil active organic carbon components and enzyme activities in pepper,and to clarify the fertilization mode to increase the content of soil active organic carbon components in pepper.Seven treatments were set up,including no fertilization(CK),single application of urea(N0),80% urea + 20% amino acid fertilizer(N20),60% urea + 40% amino acid fertilizer(N40),40% urea + 60% amino acid fertilizer(N60),20% urea + 80% amino acid fertilizer(N80)and single application of amino acid fertilizer(N100).The changes of soil physical and chemical properties,soil active organic carbon content and enzyme activity under each treatment were studied.The results showed that the combined application of amino acid fertilizer and urea could effectively increase the contents of nitrogen,phosphorus and potassium,organic matter,enzyme activity,organic carbon and its active components in soil.The content of soil organic carbon increased with the increase of amino acid fertilizer application,and the content of soil active organic carbon components and enzyme activity increased first and then stabilized or decreased slightly with the increase of amino acid fertilizer application.The soil easily oxidized organic carbon content,particulate organic carbon content,microbial biomass carbon content,cellulase activity,catalase activity and amylase activity of N60 treatment were the best:in 0-20 cm soil layer,compared with CK treatment,they were increased by 105.50%,19.43%,142.60%,126.57%,22.28% and 308.20%,respectively.In the 20-40 cm soil layer,compared with CK treatment,it increased by 39.75%,59.32%,59.00%,130.27%,33.24% and 342.16%,respectively.Correlation analysis showed that soil total organic carbon and active organic carbon components were significantly positively correlated with enzyme activity.It can be seen that the combined application of amino acid fertilizer and urea can effectively improve the soil active organic carbon content and enzyme activity in pepper,and the treatment of 40% urea combined with 60% amino acid fertilizer has the greatest potential for improvement.

In order to explore the rapid and scientific improvement model of soil fertility in newly cultivated land,it took the maize wheat rotation system of newly cultivated land as the research object,and conducted different fertilization treatment experiments (including no fertilization control (CK),organic fertilizer 15 t/ha(OF15),chemical fertilizer (MIN),organic fertilizer 7.5 t/ha+fertilizer (OF7.5+MIN),organic fertilizer 15 t/ha+fertilizer (OF15+MIN),and organic fertilizer 30 t/ha+fertilizer (OF30+MIN)).Based on the basic data of soil physical and chemical properties such as total nitrogen,alkaline nitrogen,available phosphorus,available potassium,and organic matter,the integrated fertility index (IFI) of soil nutrients was used to quantitatively and comprehensively evaluate the soil fertility of different fertilizers.The results showed that:on the basis of applying chemical fertilizers to newly cultivated land, organic fertilizers were added to improve soil available nutrients, increasing soil total nitrogen by 108.6%-149.0%, soil alkali hydrolyzed nitrogen by 253.6%-311.0%, soil available phosphorus by 78.8%-171.6%, soil available potassium by 35.6%-80.5%, soil organic matter content by 5.8%-41.9%, soil capacity by 1.0%-8.3%, soil pH value by 3.4%-7.3%, soil fertility comprehensive index by 21.6%-27.7%, and annual yield of corn and wheat by 33.2%-127.1%. The available nutrients, organic matter, soil fertility level, and annual yield of corn and wheat in newly cultivated land all showed an increasing trend with the increase of organic fertilizer application, among which 30 t/ha of organic fertilizer had the best effect. Compared with the application of organic fertilizer alone, the combination of organic fertilizer and chemical fertilizer effectively increased soil organic matter and soil comprehensive fertility index by 12.3% and 22.0%, respectively. In summary, under the conditions of this experiment, the combination of organic fertilizer and chemical fertilizer resulted in higher soil comprehensive fertility and annual crop yield compared to single application of chemical fertilizer or single application of organic fertilizer. The treatment with 30 t/ha of organic fertilizer and 2+chemical fertilizer significantly improved the soil fertility and crop yield of newly reclaimed farmland.

The aim of this study was to investigate the effects of different nitrogen application levels and base-topdressing ratio on wheat leaf physiology,source-sink regulation of grain storage and yield in the middle and lower region of Yangtze River in Anhui Province.Using Baihumai 1 as the experimental material,three nitrogen application rates(180,210 and 240 kg/ha)with different nitrogen application levels and base ratios of 5∶1∶4,7∶1∶2 and 5∶4∶1 were set;through the determination of different source-sink indexes,in order to determine the appropriate wheat nitrogen fertilizer management model in the middle and lower region of the Yangtze River.The results indicated that with increasing nitrogen application rates(0 to 240 kg/ha),wheat leaf area index(LAI),post-flowering chlorophyll relative content(SPAD),and source organ biomass allocation showed an upward trend.The grain biomass allocation during maturity and the conversion rate of post-flowering source production capacity exhibited a trend of initially increasing and then decreasing,with the highest values observed at a nitrogen application rate of 210 kg/ha.At the same nitrogen application level,under the condition of a 7∶1∶2 base-to-topdressing ratio(base fertilizer∶tillering fertilizer∶jointing fertilizer),wheat plant had the highest leaf area index,while under a 5∶1∶4 ratio,chlorophyll content was highest.The grain biomass allocation during maturity and the economic coefficient were highest with the 7∶1∶2 base-to-topdressing ratio.Under the same base-to-topdressing ratio treatment,increasing nitrogen application improved the number of wheat spikelets and effective spikes,while the thousand-grain weight decreased with increasing nitrogen application.Grain yield showed an initial increase followed by a decrease with increasing nitrogen application,and at a nitrogen application rate of 210 kg/ha and a 7∶1∶2 base-to-topdressing ratio,wheat population potential storage capacity was large,grain-to-leaf ratio was high,and grain filling index was suitable.Wheat grain yield reached its maximum.Considering both high yield and efficiency,the optimum nitrogen fertilizer application rate of 210 kg/ha and the base-to-topdressing ratio of 7∶1∶2 were the best for the rice-stubble wheat Baihumai 1 in the middle and lower region of the Yangtze River in Anhui Province,allowing for maximum potential storage capacity and yield under these conditions.

In order to improve the nutrient utilization rate,enhance the quality and economic benefits of Anthurium andraeanum.It explored the effect of slow-release fertilizer replacing water-soluble fertilizer on the quality and nutrient utilization of Anthurium andraeanum,with the aim of optimizing the production and cultivation measures of Anthurium andraeanum.This experiment used two varieties of Anthurium andraeanum,Turenza and Sierra,as test materials.Three fertilization treatments were set up:a control group(CK)with clear water,a common water-soluble fertilizer group(T),and a slow-release fertilizer group(AL).Through measuring the growth indicators such as plant height,crown width,maximum leaf length,maximum leaf width,leaf number,petiole diameter,it was found that the slow-release fertilizer treatment group(AL)had significantly better indicators than the control group(CK)and the common water-soluble fertilizer group(T).Furthermore,the chlorophyll content,dry matter accumulation,and nitrogen,phosphorus,and potassium accumulation in the plants were determined.The results showed that compared with the common water-soluble fertilizer group(T),the slow-release fertilizer group(AL)increased the total chlorophyll content by 1.9% in Sierra and 60.3% in Turenza;the dry matter accumulation in plants increased by 3.9% in Sierra and 35.4% in Turenza;the total nitrogen increased by 13.6% in Sierra and 32.1% in Turenza;meanwhile,the overall plant state and commercial value were better.Therefore,replacing common water-soluble fertilizer with slow-release fertilizer can increase the nutrient utilization rate of plants by increasing their chlorophyll content,improve the quality of Anthurium andreanum,reduce resource waste and environmental pollution,and has good prospects for future production of Anthurium andreanum potted flowers.

To investigate the impact of saline water irrigation on greenhouse gas emissions,including CO₂,N₂O,CH₄,and the soil microbial community in winter wheat fields,three types of saline water with different salinity levels(1,3,and 5 g/L,denoted as W1,W3,and W5)were employed.Field experiments were conducted at the Nanpi Eco-Agriculture Experimental Station of the Chinese Academy of Sciences from March to June 2023.The results indicated that CO₂ emissions had similar trends in the different saline water irrigation treatments during the wheat growing stages,which were high in the early stage,low in the middle stage,and high in the late stage.N₂O emissions exhibited a trend of high values in the early period and lower values in the later stages.While,CH₄ showed fluctuations between positive and negative emissions.Comparative analysis revealed that the average CO₂ and N₂O emission rates in W3 treatment were significantly lower than in W1,with reductions of 39.4% and 68.9%,respectively.The average CO₂ and N₂O emission rates in W5 treatment decreased by 21.9% and 40.0%,although the difference was not statistically significant.Saline water irrigation with different concentrations minimally affected soil microbial α-diversity but significantly altered community structure.Cluster analysis demonstrated a significant difference in microbial composition between W1 and W5,with W3 positioned between the two treatments.Correlation analysis showed that there was a significant positive correlation between CO₂ and N₂O emission rates and soil TN,while there was a significant positive correlation between N₂O emission rate and soil TN,TOC,DOC,MBC,respectively.Soil N₂O and CH₄ emission rates correlated positively with the abundance of S0134 terrestrial and Sphingomonas and Subgroup 25,respectively.Redundancy analysis(RDA)identified pH,NH₄⁺,EC,and DOC as key physicochemical factors influencing the abundance of Sphingomonas and Subgroup 25.In conclusion,irrigation with 3 g/L mildly saline water can reduce soil respiration rates and decrease agricultural carbon emissions without significantly increasing soil salinity,providing theoretical support for the development and utilization of mildly saline water resources in the North China Plain.

To investigate whether earthworm castings can affect the bacterial diversity of maize soil inside and outside the facility,so as to provide a reference for studying the difference in soil ecological quality between earthworm castings inside and outside the facility at the microbial level.Based on Illumina NovaSeq sequencing platform,16S rRNA sequencing was performed on rhizosphere soil bacteria of maize in different planting modes(different varieties of maize in and outside earthworm manure facilities and different varieties of maize in and outside conventional facilities).A total of 35 627 operational taxonomic units(OTUs)were obtained after quality control,with a total of 1 832 428 valid sequences.The OTU number of soil samples,bacterial community structure,relative abundance,the difference between dominant bacteria genera and groups,and the difference in bacterial diversity analysis were compared under different planting patterns.The OTU number of soil samples was significantly different between earthworm droppings and conventional planting mode.The OTU number of earthworm droppings was higher than that of conventional planting,but the difference was not significant between earthworm droppings and different maize varieties.The dominant microphyla of soil community structure were basically the same,but there was a large difference in the abundance of microphyla between inside and outside the facility and whether or not earthworm castings were applied,and there was little difference between different maize varieties.At the phylum level,the relative abundance of Proteobacteria and Bacteria in and outside conventional planting facilities(class D)was higher than that in and outside vermicomical planting facilities(class E),while the relative abundance of Actinobacteria and Blastomonas in and outside conventional planting facilities(class E)was higher than that in and outside conventional planting facilities(class D).At the generic level,Sphingomonas,Unclassified_Gemmatimonadaceae,Subgroup_10,Unclassified_Bacteria and Unclassified_Vicinamibacteraceae were found to be more abundant in worm castings than in conventional ones.While Unclassified_Microscillaceae,Altererythrobacter,Flavobacterium,Unclassified_Vicinamibacteraceae and Uncultured_gamma_proteobacterium,these five genus had a higher abundance in conventional cultivation than in vermicompost cultivation.The results of diversity analysis showed that the Chao1,Ace,Shannon and Simpson indices of earthworm manure planting(type E)were significantly higher than those of conventional planting(type D).The number and diversity of soil bacteria in earthworm manure planting mode were higher than those in conventional planting mode,and different planting modes significantly affected the composition of soil bacterial community.

In order to effectively control the nitrogen loss during the livestock manure composting process,a reactor was used for a simulated composting test.Fresh cattle manure as raw material,and maize straw as assist material,to investigate the effects of different clay minerals and chemical substances compound additives on nitrogen loss,nitrogen morphological transformation law and physicochemical properties during the cow manure composting process.The results showed that the compound additives were no impact on the decay process of the material.The index of seed germination rate and pH meets the standard requirements of organic fertilizer(NY525-2002).Adding clay minerals of vermiculite or bentonite,total emission of ammonia decreased by 21.83% and 14.22% than CK,respectively.While,the combination of clay mineral+acid additive could further reduce the ammonia emission.Vermiculite+calcium perphosphate(ZK+CaP)was the best treatment,the second was vermiculite+calcium dihydrogen phosphate combination,total emission of ammonia significantly decreased by 28.47% and 21.18% than single vermiculite treatment.Results of the correlation analysis showed linear correlations were found between pH and total nitrogen content(y=52.97x-351.77,r=0.83),in the pH range of 7.0-8.0.The total ammonia emission was reduced by 5.30 g/kg,because the pH decreased by 0.1 units in a certain range.Total nitrogen content increased by 6-14 percentage points compared with CK.So clay minerals were combined with calcium dihydrogen phosphate,wood acetate and calcium perphosphate,which could reduce the pH effectively,further reduce the ammonia emissions,increase the nitrogen content,and realize the effect of nitrogen preservation and fertilizer increase in the process of cow manure composting,and the combination of vermiculite+calcium perphosphate was the best treatment.

In order to explore the improvement effect of calcium fertilizer and ARC microbial agent on red earth dry land with low-calcium,the peanut variety Xianghua 522 was used as the experimental material,and two levels of calcium hydroxide fertilizer(0,750 kg/ha,code Ca₀ and Ca₅₀)and three levels of ARC microbial agent(0,30,60 kg/ha,code A₀,A₂ and A₄)were set to form six treatments to carry out pot experiment.It measured soil nutrient and soil enzyme activity in 0—20 cm arable layer soil at peanut seedling stage,flowering stage,pod setting stage and pod filling stage,and pod economic characters and yield were measured at harvest.The results showed that:single application of calcium fertilizer and the combined application of calcium fertilizer and ARC microbial agent could significantly improve the pH of soil at all growth stages,but ARC microbial agent had little effect on it.Compared with CK(Ca₀A₀),Ca₅₀A₂ and Ca₅₀A₄ significantly increased the content of hydrolyzable nitrogen in soil in the whole stage and the content of available phosphorus in soil in the first three growth stages;the content of available potassium in soil of Ca₅₀A₄ was higher than CK in general,and it was significant at seedling stage and pod setting stage;compared with CK,Ca₅₀A₀ significantly increased the content of exchangeable calcium in soil in four stages,with an increase of 23.78%—56.21%;the content of calcium ion in soil with calcium fertilizer application was significantly higher than that without calcium fertilizer application(the flowering stage was not significant),and it was little affected by ARC microbial agent;the content of organic matter in soil remained stable in the whole growth stage,but Ca₅₀A₄ and Ca₅₀A₂ were significantly higher than CK in each growth stage.Compared with CK,the soil sucrase activity of soil each treatment was significantly increased in four stages,and the increase was the largest in Ca₅₀A₄,ranging from 50.79% to 162.56%;the protease activity of soil was significantly increased by Ca₅₀A₂ in four stages with an increase of 26.58%—244.63%;the acid phosphatase activity of soil was significantly increased by Ca₅₀A₄ and Ca₀A₂ during the whole growth stage;the catalase activity of soil in all treatments showed a decreasing trend in general.All treatments could increase the yield of peanut pod in different degrees,and the effect of calcium fertilizer application was greater than that of ARC microbial agent,among which Ca₅₀A₄ had the best effect,with the pod weight per plant increasing by 12.29%,mainly increased the pod number per plant and the full pod number per plant.To sum up,the combined application of calcium fertilizer and ARC microbial agent has a good interaction effect on improving soil nutrient content,stimulating soil enzyme activity and increasing peanut yield,and the best effect is 750 kg/ha calcium fertilizer+60 kg/ha ARC microbial agent(Ca₅₀A₄),which can provide a theoretical basis for green and high yield cultivation of peanut.

This study systematically investigates the effects of silicon-modified biochar (MSC) on the chemical properties of acidic soil,organic carbon and silicon fractions,and the growth of tomato plants.Silicon-modified biochar was prepared,with a focus on investigating its impacts on carbon and silicon chemical fractions,and the availability in acidic soils;tomato growth and soil microbial activity were also evaluated.The results showed that silicon-modified biochar significantly increased soil pH,cation exchange capacity,electrical conductivity,available phosphorus and potassium.MSC also raised the levels of water-soluble sodium and iron in the soil and enhanced the activities of hydrogen peroxidase and sucrase enzymes,thereby improving soil quality.Both biochar modification and unmodified biochar significantly increased the content of different carbon fractions in the soil.Compared with unmodified biochar,silicon-modified biochar significantly increased soil microbial biomass carbon(21.9%) and water-soluble organic carbon (898.3%).Furthermore,silicon-modified biochar significantly increased the contents of soil available silicon,water-soluble silicon,free silicon,active silicon,iron-manganese-bound silicon and amorphous silicon by 362.6%,158.9%,18.1%,34.9%,193.8%,and 74.1%,respectively.Meanwhile,the application of biochar promoted the growth of tomato plants and the absorption of silicon nutrients,with modified biochar showing more pronounced effects.The accumulation of plant dry matter,silicon content,and absorption rate increased by 82.0%,98.9%,and 261.5%,respectively.In summary,silicon-modified biochar significantly affected the carbon and silicon chemical forms and transformation in the soil,increased soil effectiveness and enzyme activity,thereby promoting nutrient absorption and growth of crops,demonstrating its good potential application in agricultural production.

To explore the effects of soil phosphorus levels and exogenous microbial agents on soil functioning(soil physico-chemical properties,soil enzyme activities,and arbuscular mycorrhizal fungi(AMF)community composition and structure)of the rhizosphere soil of maize,a two-factor interaction experiment was conducted to study the effects of two levels of low phosphorus and normal phosphorus and four treatments of inoculation with AMF,phosphate-solubilizing bacteria(PSB),AMF-PSB and no inoculation of exogenous agent(CK)on rhizosphere soil indexes in different growth stages of maize.The results showed that the soil total phosphorus content was the highest at jointing stage and silking stage under the condition of normal phosphorus level+AMF treatment,while the soil available phosphorus content was the highest at jointing stage and mature stage under the condition of normal phosphorus level+AMF treatment.At jointing stage and silking stage,alkaline phosphatase activity was the highest under low phosphorus+AMF treatment,and the activity of alkaline phosphatase under low phosphorus+AMF treatment and low phosphorus+PSB treatment was higher than that under normal phosphorus level.Under low phosphorus level,total phosphorus content and available phosphorus content were higher than CK treatment,and the increase rate was higher than that under normal phosphorus level.At low phosphorus level,soil pH value was lower than CK treatment under the condition of inoculated foreign bacteria,and also lower than CK treatment under normal phosphorus level at jointing stage.Under the low phosphorus level,the CK treatment had the highest observed number of AMF community OTUs and α-diversity indexes,while under the normal phosphorus levels,the observed number of OTUs and α-diversity index in the CK treatment group were lower than those in the AMF and PSB treatments.Non-metric multidimensional scaling analysis indicated that the composition and structure of soil AMF communities were convergently regulated by the types of inoculated exogenous microorganisms.In summary,inoculating AMF and PSB agents in low-phosphorus alkaline maize fields in northern China can improve soil physicochemical properties and increase soil alkaline phosphatase activity,but it also increases competition and exclusion among soil AMFs.

To study the photosynthetic characteristics,fluorescence parameters and yield response to phosphorus in maize,and to clarify the optimal phosphorus application rate for maize under drip irrigation and water fertilization technology.Providing solid theoretical basis and technical support for high-yield and high-efficiency cultivation of maize in Ningxia region.The experiment was carried out at Pingjipu Farm,Yinchuan,Ningxia,from 2019 to 2020,with six phosphorus treatments in the order of 0(P0),60(P1),120(P2),180(P3),240(P4),and 300 kg/ha(P5).Analysis of the changing patterns of photosynthetic and fluorescence parameters of spring maize leaves and their correlation with yield under different phosphorus fertilizer treatments.In two years,during the big bell mouth stage,leaf area index (LAI) was increased by 4.21% to 12.78% and 4.68% to 15.60% for P3 compared to other treatments,respectively.Phosphorus fertilizer at 180 kg/ha was most effective in promoting leaf area index and photosynthetic potential(LAD) of maize.LAD was significantly increased by 14.42% under P3 treatment compared to no phosphorus fertilizer treatment during the full two year period.The photosynthetic characteristics of maize responded differently to the intensity of phosphorus application,and as the intensity of phosphorus application increased,the net photosynthetic rate (Pn) all reached the maximum value after the stamen pumping stage,and at the R1 stage of the 2 years,the Pn was significantly increased by 10.68% under the P3 treatment as compared to the no-phosphorus-fertilizer treatment.The coefficient of determination (R²) was 0.926 5,0.889 9,and 0.832 0,respectively.Phosphorus application increased the maize photosystem Ⅱ composite performance index (PI),which had its maximum peak at the R1 stage in 2 years,and PI increased by 1.12% to 8.50% and 8.47% to 15.40% under the P3 treatment compared with the other treatments,respectively.The maximum yield was obtained at 180 kg/ha of phosphorus application,which was 17.27% higher as compared to no phosphorus treatment.Based on the analysis of the yield fitting equation,it was shown that the maximum corn yield of 13 823.84 kg/ha was reached at 179.34 kg/ha of phosphorus applied.Pearson's correlation analysis showed that appropriate leaf area index significantly affected maize yield in the late stage,and the photosynthetic parameters all had highly significant effects on maize yield completion;principal component analysis showed that the P3 treatment had the highest composite score for the optimization effect on maize yield.Reasonable transportation of phosphorus fertilizer can effectively ensure higher SPAD value,PSⅡ reaction center activity,improve the capture and utilization of light energy in spring maize,and promote photosynthesis,so as to improve the yield and economic benefits of maize.

To compare the effects of different nitrogen enhanced fertilizer on apple growth and to identify suitable nitrogen enhanced fertilizer and application methods for apple cultivation,this study examined the impact of four different types of nitrogen enhanced fertilizer on apple growth,yield,quality,and soil nitrogen supply capacity.The experiment consisted of seven treatments:no nitrogen fertilizer(CK),regular application of ordinary urea by farmers(U),coated urea mixed with ordinary urea 3∶7(CU1),basal application of coated urea and follow-up application of ordinary urea(CU2),loss-control urea(KSU),stabilizing urea(WDU),and humic acid stabilizing urea(FZU).A field experiment was conducted in Qixia City,Shandong Province,to analyze the effects of different fertilization treatments on the growth,yield,and quality of 6-year-old Golden Crown apple trees,as well as nitrogen utilization and soil nitrogen supply capacity.The results demonstrated that the application of diverse synergistic nitrogen fertilizers could markedly enhance spring and autumn growth,elevate leaf SPAD,and enhance apple yield and quality.Among these,the yield of the FZU treatment exhibited a significant increase of 8.89% in comparison to that of the control.The Vc content of the fruits of the CU1 treatment was found to be significantly increased by 66.73% in comparison to the U treatment.Furthermore,the CU1 treatment demonstrated the most pronounced impact on the improvement of growth in both spring and autumn.Nitrogen enhanced fertilizer had been demonstrated to significantly enhance nitrogen accumulation in new shoots and fruit nitrogen accumulation,nitrogen fertilizer agronomic efficiency,nitrogen fertilizer bias productivity and nitrogen utilization in the middle and late stages of apple fertility.Of these,the FZU treatment had been observed to exert the most pronounced effect.The nitrogen accumulation of new shoots in FZU treatment was significantly increased by 37.25%,15.91% and 37.85% compared with that in U treatment at bud differentiation,fruiting and ripening stages,respectively.The CU2 treatment was found to have the most beneficial effect on nitrogen utilization.Nitrogen enhanced fertilizer treatments demonstrated the capacity to significantly enhance the nitrate and ammonium content of soil.Among these treatments,the FZU treatment exhibited the most pronounced effect.The FZU treatment was observed to enhance soil urease activity during the flowering and bud differentiation stages.Additionally,the WDU and FZU treatments were found to significantly reduce the nitrification of soil ammonium and nitrogen loss.The {\mathrm{NO}}_3^{-}-N of the FZU treatment was concentrated at a depth of 20—60 cm soil,which was consistent with the distribution of apple roots in the soil and reduced the risk of {\mathrm{NO}}_3^{-}-N leaching.A comprehensive analysis demonstrated that the FZU treatment exhibited clear advantages in promoting apple growth,increasing apple yield and quality,and enhancing soil nutrient supply capacity.Consequently,the FZU treatment was identified as the optimal treatment.

Improper application of soybean fertilizer can lead to late ripening,lodging,worsening of diseases and pests,and a decrease in fertilizer and yield benefits,to improve fertilizer efficiency and fully tap into the potential of soybean yield and quality,therefore,this article investigates the effects of seven fertilization modes F1(basic application of 3 000 kg/ha organic fertilizer+300 kg/ha chemical fertilizer),F2(basic application of 3 000 kg/ha organic fertilizer+150 kg/ha chemical fertilizer+topdressing 150 kg/ha chemical fertilizer),F3(basic application of 3 000 kg/ha organic fertilizer+225 kg/ha chemical fertilizer+topdressing 75 kg/ha chemical fertilizer),F4(basic application of 1 500 kg/ha organic fertilizer+75 kg/ha chemical fertilizer+topdressing 225 kg/ha chemical fertilizer),F5(basic application of 300 kg/ha chemical fertilizer),F6(basic application of 150 kg/ha chemical fertilizer+topdressing 150 kg/ha chemical fertilizer)and F7(basic application of 225 kg/ha chemical fertilizer+topdressing 75 kg/ha chemical fertilizer)on soybean growth,development,photosynthesis,yield,and quality through field experiments using a single factor experimental design.The results showed that increasing the application of organic fertilizer significantly enhanced the dry weight of soybean roots when compared to applying chemical fertilizer alone,applying chemical fertilizer alone with a base to top dressing ratio of 3∶1 was the most beneficial for increasing root dry weight.The combination of organic fertilizer and chemical fertilizer resulted in higher fresh leaf weight,dry leaf weight,fresh stem weight,dry stem weight per plant,as well as higher fresh weight and dry weight per plant when compared to single application of chemical fertilizer,and there were no significant differences in the above indicators among the treatments treated with single application of chemical fertilizer.The combination of organic fertilizer and chemical fertilizer increased the number of leaves per plant and leaf area index of soybean at pod bearing stage and filling stage,under the condition of no organic fertilizer application,the base to top dressing ratio of 3∶1 of chemical fertilizer was beneficial for improving the number of leaves and leaf area index of soybean.Compared to single application of chemical fertilizer,combined application of organic fertilizer and chemical fertilizer increased the photosynthetic rate at flowering and filling stages by 16.69%—21.66% and 14.99%—30.66%,respectively,unreasonable base to top dressing ratio of chemical fertilizer or reducing organic fertilizer dosage could affect the chlorophyll content and photosynthetic rate of soybean in the middle and later stages of growth and development.Increasing organic fertilizer application amount could increase soybean yield and protein content,while reduce fat content,applying chemical fertilizer alone with a base to top dressing ratio of 3∶1 was the most conducive to increasing yield.Therefore,it can be concluded that the combination of organic fertilizer and chemical fertilizer is significantly better than that of single application of chemical fertilizer in improving soybean growth and development,photosynthesis,yield,and quality,in addition,single application of chemical fertilizer performs better with a base to top dressing ratio of 3∶1.

To study the effects of ridge height on soil heat status,root growth,and tobacco maturity tolerance in tobacco planting,a 2-year field experiment was conducted using the flue-cured tobacco variety Yueyan 97 as the test material from 2022 to 2023.Three treatments were set up,including a ridge height of 30 cm(CK),a ridge height of 38 cm(T1),and a ridge height of 46 cm(T2),to analyze the changes in soil temperature and heat flux,root appearance and growth indicators,root vitality,and tobacco maturity related indicators under different ridge heights.The results indicated that the daily temperature difference in soil varies with the depth of the soil layer,and the daily temperature difference in the surface layer of the soil was the largest.Increasing ridge height can increase the average temperature of tobacco planting soil by 0.4-1.8 ℃ and increase soil heat flux by 4-56 W/m².In the 2 a experiment,the maximum increase in root length for a ridge height of 38 cm compared to a ridge height of 30 cm was 27.26%,the maximum increase in root dry mass was 26.21%,and the maximum increase in root vitality was 14.97%,with significant differences.Compared with a ridge height of 30 cm,the soluble protein content,peroxidase activity,and cell membrane stability index of a ridge height of 38 cm increased by 17.99%,27.82%,and 9.05 percentage points(2022),respectively and by 10.23%,12.44%,and 8.16 percentage points(2023),respectively.The maximum decrease in malondialdehyde content was 24.84% and 44.43%,respectively.Correlation analysis showed that root activity was significantly negatively correlated with malondialdehyde content,peroxidase activity was extremely significantly positively correlated with root growth indexes, and soluble protein content was significantly positively correlated with root length.In summary,increasing ridge height is beneficial for improving the thermal status of tobacco planting soil,promoting root growth,enhancing root vitality,enhancing leaf antioxidant capacity,and enhancing tobacco maturity tolerance.A ridge height of 38 cm is an appropriate ridge height for promoting root growth and improving tobacco maturity tolerance in southern tobacco regions.

In order to explore the effects of different irrigation methods and nitrogen fertilizer management on late rice growth,development,yield formation,and nitrogen use efficiency,Y Liangyou 911 was used as test material.Two irrigation methods(W1.flooded irrigation;W2.moistening irrigation) and three nitrogen fertilizer managenments base,tiller,ear and grain fertilizer ratios(N1:5∶3∶2,N2:3∶4∶3 and N3:3∶4∶2∶1) were designed.No fertilization served as the control (CK1.flooded irrigation;CK2.moistening irrigation).Leaf area index,SPAD value of rice leaves,dry matter mass,yield formation and nitrogen use efficiency were determined under each treatment combination.The results showed that compared with W1,the LAI of rice treated with W2 was lower in the early growth stage and higher in the middle and late growth stages.The SPAD value of W1 treatment was higher,but there was no significant difference in SPAD value in the late growth period.Under the same irrigation conditions,compared with N1,N2 and N3 treatments it could delay the decline of LAI and SPAD values in the late growth period of rice.W2 treatment could significantly increase rice dry matter accumulation by 6.61%-16.37% compared with W1 treatment.Under nitrogen fertilizer treatment,the dry matter mass was higher in the early and middle stages of growth with N1,and the dry matter mass was higher in the later stages with N1 and N3.The yield increase of W2 mode was 7.59%-10.47% compared with W1 mode.The yield of W2N3 treatment was 3.24%-14.53% higher than that of other treatment.Although the effective panicle number was lower in W2N3 treatment,other yield components were increased,which resulted in higher yield.During the two years,W2N2 and W2N3 had higher values of total nitrogen accumulation and nitrogen absorption efficiency,W2N3 had higher values of nitrogen agronomic utilization,nitrogen partial productivity and nitrogen harvest index,and W1N3 had the higher value of physiological nitrogen utilization.In conclusion,irrigation methods and nitrogen management significantly affect rice yield and nitrogen uptake and utilization.The W2 (moistening irrigation) coupled with N3 (base fertilizer∶tillering fertilizer∶ear fertilizer∶grain fertilizer=3∶4∶2∶1) nitrogen management method is more conducive to rice dry matter accumulation,yield improvement and efficient use of nitrogen fertilizer,which can not only meet high yield,but also play a role in water saving.It is the best coupling method of water and fertilizer.

In order to clarify the effect of fertilizer reduction on wheat yield and starch particle size distribution characteristics, seven fertilization treatments were set up with wheat varieties Longke 1109 and Yangmai 25 as materials.No nitrogen fertilizer (CK),farmer's customary nitrogen application rate (ternary compound fertilizer 750 kg/ha+ topdressing 150 kg/ha urea,CF),slow-release fertilizer 900 kg/ha one-time base application (SF900),slow-release fertilizer 750 kg/ha one-time base application (SF750),slow-release fertilizer 600 kg/ha one-time base application(SF600),slow-release fertilizer 750 kg/ha base application+topdressing 150 kg/ha urea (S750T),slow-release fertilizer 600 kg/ha base application + topdressing 150 kg/ha urea (S600T).The effects of slow-release fertilizers on grain yield and starch particle size distribution of wheat were analyzed.The results showed that under the condition of reducing fertilizer application,the spike number first increased and then decreased,the grain number per spike decreased,the 1000-grain weight increased,and the yield of wheat under SF750 treatment was the highest.The content of wet gluten and protein decreased and the content of starch increased in two stubble.The volume and proportion of surface area of B-type starch in strong and weak grains first increased and then decreased,while the proportion of the volume and surface area of A-type starch grains decreased first and then increased in dry stubble.In rice stubble,While the proportion of the volume and surface area of B-type starch grains increased,while those of A-type starch grains decreased.The gelatinization parameters of the two stubble decreased.In summary,the reduction of fertilizer application mainly affects the grain size distribution of endosperm starch,decreases indicators such as gelatinization parameters,and increases grain yield and starch content,which further decreases the content of wet gluten and protein.Compared with the customary nitrogen application rate of farmers,reducing fertilizer application increases wheat grain yield,increases wet gluten and protein content,and decreases starch content.

This study revealed the changes of bacterial community structure and diversity in facility cucumber rhizosphere soil affected by different reactors,aiming at providing theoretical basis and practical basis for cucumber rhizosphere soil improvement and sustainable utilization of protected soil.This experiment was based on the V3-V4 region of the 16S rRNA gene,seven treatments namely,original greenhouse soil(CK),untreated cucumber rhizosphere soil for 100 days(CK1) and 200 days(CK2),corn straw bioreactor-treated cucumber rhizosphere soil for 100 days(S1)and 200 days (S2),and sheep manure bioreactor-treated cucumber rhizosphere soil for 100 days(M1)and 200 days(M2).High-throughput sequencing technology using Illumina Miseq was used to analyze the diversity,structure,and physical and chemical properties of the bacterial communities in the rhizosphere soils of different bioreactor treatments on facility cucumber.The results showed that 6 344 OTUs were obtained from soil samples after sequencing,which mainly belonged to 39 phyla,315 orders and 980 genera.M2 treatment could improve the bacterial richness in cucumber rhizosphere soil and significantly increase the diversity of bacterial community.At the phylum level,the dominant population structure of bacterial phylum in soil treated by corn straw bioreactor and sheep manure bioreactor was similar,among which Actinobacteriota and Proteobacteria were the dominant phylum.At the genus level,norank_f_JG30-KF-CM,Arthrobacter,norank_f_norank_o_Gaiellales,norank_f_67-14,Blastococcus,Gaiella and Marmoricola were significantly different among different treatments.According to the composition of bacterial community abundance,M2 and S2 treatments increased the relative abundance of some beneficial bacterial groups in cucumber rhizosphere to some extent.RDA analysis showed that the soil bacterial community was significantly affected by soil environmental factors,and the contents of ammonium nitrogen(P=0.015),total potassium(P=0.002)and available potassium(P=0.005)had significant effects on the bacterial community.Therefore,M2 treatment can improve the bacterial richness in facility cucumber rhizosphere soil,increase the diversity of bacterial community and change the bacterial community structure,which is beneficial to the improvement of facility cucumber rhizosphere soil.

In order to explore the molecular mechanism of low nitrogen response in quinoa, low nitrogen response genes were screened to reveal the adaptive changes in quinoa response to low nitrogen.Based on the seedling growth observation and chlorophyll synthesis detection,we analyzed the transcriptome changes of quinoa after 5 d and 30 d under nitrogen deficiency conditions.The results showed that roots were preferentially developed under nitrogen starvation condition.Older leaves turned yellow or dropped down under both low nitrogen and nitrogen starvation conditions,therefore younger leaves could maintain green.Higher NUE was shown in both low and nitrogen starvation conditions.GO enrichment analysis indicated that significantly differential expressed genes were mainly involved in integral component of membrane,membrane,oxidation-reduction process,metabolic process,ATP binding,and metal ion binding.After 5 d of low or nitrogen starvation supply,KEGG enrichment analysis showed that phenylpropyl biosynthesis and glutathione metabolism were the most significant metabolic pathways compared with high nitrogen.After 30 d of treatment,the most significant metabolic pathway was the carbon metabolic pathway.The key genes in response to low nitrogen in quinoa were further explored.The results showed that peroxidase,glutathione S-transferase and ascorbate peroxidase genes were up-regulated and their expressions were higher after 5 days of low nitrogen and nitrogen deficiency treatment.The genes of phosphoglycerate kinase,cysteine synthetase,glyceraldehyde 3-phosphate dehydrogenase (NADP)and phosphoenolpyruvate carboxylase were up-regulated and the expression levels were higher after 30 days of low and low nitrogen treatment.The results of qRT-PCR agreed with the RNA-Seq.

In order to screen out suitable water and nitrogen combinations for watermelons in Yellow River irrigation area of Ningxia, different water and nitrogen treatments were designed to study the effects of water and nitrogen interaction on SPAD value of watermelon leaves, fruit quality,yield and nitrogen uptake and utilization. The results showed that SPAD values were higher by W1N4,W2N3,W2N4,W3N3 and W3N4 treatment,the quality was better under nitrogenous fertilizer amounts at N2 and N3.The yield was the highest under W3N4 treatment,reaching 76 565.36 kg/ha and increased by 8.34% to 37.57% compared with other treatments significantly.Followed by W3N2 and W3N3 treatment.Compared with other levels,when the irrigation water level was W1,the water use efficiency of facility watermelon irrigation was higher.Among them,the irrigation water use efficiency of W1N3 and W1N4 treatment was higher,reaching 43.91,45.32 kg/ha respectively,while it was significantly increased by 14.00% to 56.40% from other treatments.Fruit nitrogen accumulation and total nitrogen accumulation under W3N4 treatment were all the highest compared with other treatments significantly,increasing by 22.75% to 192.36% and 17.00% to 123.39% respectively compared with the other treatments.Partial factor productivity of nitrogen and nitrogen fertilizer utilization rate under W3N2 treatment were all the highest compared with other treatments significantly.Partial factor productivity of nitrogen increased by 11.00% to 343.68%separately compared with the other treatments and nitrogen fertilizer utilization rate increased by 3.34 to 10.02 percentage points compared with other treatments.The correlation analysis showed that SPAD,the center of soluble solids,Vc,yield,irrigation water use efficiency and nitrogen accumulation,were all significantly positively correlated with each other,and they were significantly negatively correlated with partial factor productivity of nitrogen and nitrogen use efficiency,the edge of soluble solids was positively correlated with nitrogen accumulation of the plants,and negatively correlated with partial factor productivity of nitrogen and nitrogen use efficiency.To sum up,the watermelon had better quality when nitrogenous fertilizer amounts were N2(80 kg/ha) and N3(160 kg/ha),the yield-increasing effect was the best under the combination of water amount for W3(2 200 m³/ha)and nitrogenous fertilizer amount for N4(240 kg/ha).The interaction between high amount of irrigation water and nitrogenous fertilizer application is beneficial to the nitrogen absorption in watermelon,and the interaction between low nitrogen application amount and high nitrogenous fertilizer amount is conducive to utilization of nitrogen fertilizer.

Abstract:To explore the effects of phosphorus fertilizer reduction ratio and phosphorus fertilizer management method on tomato yield,phosphorus utilization rate and soil fertility level under simultaneous reduction of chemical fertilizer nitrogen,phosphorus and potassium in high fertilizer application areas,an experiment was conducted in a greenhouse located in Dingxing County,Hebei Province.Overwintered long-season tomato was chosen as the experimental plant.Treatments included CF(N-P₂O₅-K₂O,1 009.5-774.0-1 458.0 kg/ha),P1(N-P₂O₅-K₂O,750.0-375.0-1 125.0 kg/ha),PB2(N-P₂O₅-K₂O,750.0-225.0-1 125.0 kg/ha),PT2(N-P₂O₅-K₂O,750.0-225.0-1 125.0 kg/ha),P3(N-P₂O₅-K₂O,750.0-75.0-1 125.0 kg/ha)and P4(N-P₂O₅-K₂O,750.0-0.0-1 125.0 kg/ha).Fertilizer phosphorus was applied basally in the PB2 treatment,and the other fertilizer-reduced treatment fertilizer phosphorus was applied in a "Basal dressing and topdressing" method.The result showed that compared to CF,tomato yield of PT2 treatment over the three-year period revealed an average increase of 12.0%,with the highest increase.After three years of fertilizer reduction,the root dry weight of P1,PB2 and PT2 significantly increased,along with improvements in the chemical phosphorus fertilizer utilization rate,phosphorus fertilizer agronomic utilization rate,and the chemical phosphorus fertilizer harvest index.Compared to CF,PT2 treatment resulted in an increase in root shoot ratio of 48.2%, phosphorus fertilizer recovery rate and phosphorus fertilizer harvest index increased by an average of 32.9 and 2.7 percent points, phosphorus fertilizer agronomic utilization rate was 9.02 times higher than that of CF.PT2 treatment was the highest among all fertilizer reduction treatments.Compared to the CF treatment,soil $NO_3^{-}$-N,Available P and Available K contents were reduced by an average of 8.2%—14.9%,4.4%—19.9%,and 7.3%—24.8%,respectively,over the three-year period.In conclusion,a 35.2% reduction in chemical fertilizer,which included a 70.9% decrease in chemical phosphorus fertilizer,did not have a negative impact on yield in greenhouses with excessive fertilizer use.Additionally,the combination of "Basal dressing and topdressing" method for phosphate management enhances tomato yield in comparison to basal dressing alone.This method also reduces available phosphorus content and increases the efficiency of chemical phosphorus fertilizer utilization.

In order to investigate the effect of reducing nitrogen and increasing density on the yield formation characteristics of ratooning rice,hybrid rice variety Chuangliangyou 669 was used as the material to conduct two years of field experiments under conditions of three nitrogen application rates(N1:180 kg/ha;N2:153 kg/ha;N3:126 kg/ha)and two plant row spacing(M1:20.0 cm×16.7 cm;M2:16.7 cm×16.7 cm).The results showed that:reducing nitrogen reduced the leaf area index(LAI)of ratooning rice,but increasing density within a reasonable range of nitrogen reduction could increase the LAI of the main and ratooning seasons.The LAI of N1M2 and N2M2 was higher in the interaction treatments.Reducing nitrogen and increasing density both reduced the SPAD value of ratooning rice leaves,but the effect of density was not significant.Reducing nitrogen led to a decrease in dry matter weight,while increasing density could significantly increase dry matter weight.The interaction treatment of N1M2 and N2M2 had a higher dry matter weight.Reducing nitrogen reduced the yield of ratooning rice,but increasing density within a reasonable range of nitrogen reduction could increase yield.The interaction treatment of N1M2 and N2M2 had a higher yield.Reducing nitrogen significantly reduced the number of effective panicles in the main season,the total number of grains per panicle,and the regeneration rate and number of effective panicles in the ratooning season.However,increasing density had a compensatory effect on the number of panicles.Reasonable nitrogen reduction and density increase(N2M2)could coordinate the relationship among yield components and achieve higher yields.The correlation analysis showed that reasonable nitrogen reduction and density increase increased the effective number of panicles and total grains per panicle in the main season,as well as the effective number of panicles in ratooning season mainly by increasing LAI and dry matter weight of the main and ratooning season,and thereby improving the yield of ratooning rice.Overall,the nitrogen reduction and density increase treatment N2M2(nitrogen rate of 153 kg/ha,plant row spacing of 16.7 cm×16.7 cm)can save 15% nitrogen and achieve a higher yield.

Soil organic carbon and humus components are affected by soil quality,fertilization management measures and other factors.In order to clarify the regulation effect of long-term chemical fertilizer application on soil organic carbon(SOC)and soil humus components in different soil layers,a 43 a(2021)long-term fertilization experiment was conducted in Laiyang,Shandong Province.Six treatments were selected:low nitrogen fertilizer(N1),high nitrogen fertilizer(N2),high nitrogen fertilizer combined with phosphorus fertilizer(NP),high nitrogen fertilizer combined with potassium fertilizer(NK),high nitrogen combined with phosphorus and potassium fertilizer(NPK)and no fertilizer control(CK).The results showed that compared with CK,N1 could significantly increase the SOC content of 0—5 cm,with an increase of 22.84%.Single nitrogen fertilizer treatment could significantly increase the SOC content of 5—10 cm,with an increase of 20.94% and 28.60% in N1 and N2,respectively.N1 could significantly increase the SOC content of 10—20 cm,with an increase of 17.05%,while other treatments had no significant change.Compared with CK,N1 could significantly increase the content of humic acid(HA)in 10—20 cm and 20—30 cm soil layers,with an increase of 22.86% and 40.49%,respectively,while there was no significant change in 0—10 cm soil layer.NP could significantly increase the content of fulvic acid(FA)in 0—5 cm and 5—10 cm soil layers by 89.44% and 124.63%,respectively.NK could significantly increase the content of FA in 10—20 cm soil layer by 100.22%,and NPK could significantly increase the content of FA in 20—30 cm soil layer by 107.48%.N1 could significantly increase the content of humin(Hu)in 0—5 cm soil layer,with an increase of 69.34%.N2 could significantly increase the content of Hu in 5—10 cm soil layer,with an increase of 66.18%.N1 could significantly increase the content of Hu in 10—20 cm soil layer,with an increase of 79.50%,while there was no significant change in 20—30 cm soil layer.In summary,under the conditions of this experiment,long-term application of chemical fertilizers can effectively improve the fixation of soil organic carbon in non-calcareous fluvo-aquic soil and change the composition of soil humus,and the effects of different fertilization strategies are quite different.Among them,the effect of single application of nitrogen fertilizer on carbon sequestration is better.

Calcium and potassium are important mineral nutrient elements in wheat.It is significant to explore the related genetic mechanisms and effects on human nutritional health.To provide a theoretical basis for biofortification breeding of trace elements in wheat grains,we used 164 F₆ recombinant inbred lines(RILs)derived from Avocet/Chilero(AC)and 175 F₆ RILs derived from Avocet/Huites(AH).Our investigation focused on phenotypic variations in grain calcium(GCa)and grain potassium(GK)content in five environments.QTL mapping was conducted with diversity arrays technology(DArT)chip.Nineteen QTLs associated with grain calcium content were identified,distributed on chromosomes 1A,1D,2A,2B,3A,3D,4A,4B,4D,5A,5B,7A,7B,and 7D,explaining 3.23%—16.29% of phenotypic variation.Simultaneously,23 QTLs linked to grain potassium content were identified on chromosomes 1B,2A,2B,3A,3B,4A,4D,5A,6A,6B,and 7D,explaining 3.31%—24.66% of phenotypic variation.QGCa.haust-1A,QGCa.haust-AC-5A and QGK.haust-AC-2A.2 were located in multiple environments.QGCa.haust-1A and QGCa.haust-AC-5A explained 7.82%—12.72% and 9.68%—15.57% of phenotypic variation,and the physical intervals were 498.67—532.21 Mb and 461.52—486.26 Mb,respectively.QGK.haust-AC-2A.2 explained 8.15%—15.20% of phenotypic variation,with a physical range of 354.61—462.37 Mb.The genetic effect analysis of QGCa.haust-1A,QGCa.haust-AC-5A,and QGK.haust-AC-2A.2 showed that each locus effectively increased the calcium and potassium content in wheat grain.Aggregation effect analysis indicated that the lines with QGCa.haust-1A and QGCa.haust-AC-5A effect loci had highly significantly higher calcium content than those with only a single locus.In summary,three stable loci of grain calcium and potassium content are mapped on chromosomes 1A,2A,and 5A,which could significantly increase calcium and potassium content in wheat grain.

To explore the effects of fertilizer reduction and organic fertilizer application on physicochemical properties and microbial community structure of tobacco-planting soil,and provide theoretical reference for fertilizer reduction and rational application of organic fertilizer in tobacco production.Using conventional fertilization without organic fertilizer as control(CK),Illumina high-throughput sequencing technology combined with bioinformatics,the changes of soil physical and chemical properties and microbial community structure under different treatments such as 10% reduction of fertilizer(T1),10% reduction of fertilizer+sesame cake fertilizer(T2),10% reduction of fertilizer + humic acid fertilizer(T3),and 10% reduction of fertilizer + sesame cake fertilizer + humic acid fertilizer(T4)were analyzed.The results showed that compared with CK,soil nutrient content and soil enzyme activity decreased under T1 treatment,and soil physical properties were slightly improved.Combined with organic fertilizer,soil nutrient and physical properties were further improved,bulk density decreased,moisture content and porosity increased,and the contents of available phosphorus and available potassium under T2 and T4 treatment were significantly higher than those under CK and T1 treatment.The enzyme activity of soil treated with organic fertilizer increased significantly.Combined application of organic fertilizer increased the bacteria and fungi in tobacco-growing soil,among which the dominant bacteria were Proteobacteria and Actinobacteriota.Followed by Firmicutes,Bacteroidota,Chloroflexi and Acidobacteriota.The dominant fungal groups are Ascomycota,Anthophyta,Mortierellomycota,Chlorophyta,Ciliophora and Basidiomycota.The Alpha diversity index showed that the reduction of fertilizer decreased the richness of microbial community,but the combined application of organic fertilizer increased the diversity index of bacterial and fungal communities,and the bacterial community richness increased more significantly.RDA analysis showed that the important soil physicochemical factors affecting soil microbial community structure and diversity included organic matter,available potassium,alkali-hydrolyzed nitrogen,available phosphorus and soil physical properties,etc.Soil physicochemical factors had a greater impact on bacterial community structure.In conclusion,under the condition of fertilizer reduction,organic fertilizer combined with organic fertilizer can significantly improve soil nutrients,physical properties,soil enzyme activity and microflora structure,especially when combined with sesame cake fertilizer and humic acid fertilizer treatment.

To improve the applicability of biochar in saline-alkali agroecosystem,the effect and microbial mechanism of modified biochar were studied.In a 2-year field experiment,common biochar(4.5 t/ha),nitrogen-rich modified biochar(7.5 t/ha)and phosphorus-rich modified biochar(15.0 t/ha)were added to investigate their impact on crop grain yield,soil physicochemical properties and soil microbial diversity.It had been observed that the addition of biochar enhanced the quality of saline-alkali soil,with nitrogen-rich modified biochar and phosphorus-rich modified biochar demonstrating more notable effects.Biochar could boost crop yield,improve soil structure and reduce soil bulk density in saline-alkali land.The effects of the three biochar types were not consistent.Among them,the application of 15.0 t/ha phosphorus-rich modified biochar showed favorable responses,with grain yield of(8.92±0.12)t/ha,representing a 110% increase compared to the control group.Biochar affected soil microbial diversity.Common biochar increased soil microbial diversity,whereas phosphorus-rich modified biochar decreased it.With the continuous addition of biochar,soil physical and chemical properties could affect the relationship between soil microorganisms and plant structure,weakening their relationships.In this study,the application of 15.0 t/ha phosphorus-rich modified biochar was recommended to improve saline-alkali agroecosystem.

To clear under the condition of slow release nitrogen fertilizer applying different content of maize development rule of the diurnal change of photosynthetic characteristics and growth,the light response curve was to fit,so as to farming-pastoral zone of spring maize cultivation and nitrogen utilization to provide theoretical basis.This study took Guangde 5 as the research object,and based on the long-term positioning experiment in 2018,the leaves ear position in spinning—tasseling stage of maize were mesured and analyzed under six nitrogen gradient of N 0(N0,CK), 120(N8), 180(N12), 240(N16), 300(N20),360(N24) kg/ha in 2019 and 2020. SPAD value, intercellular carbon dioxide concentration, stomatal conductivity, diurnal variation of net photosynthetic rate, transpiration rate, light response curve and dry matter accumulation rule.The results showed that with the increase of nitrogen fertilizer application, the changes of SPAD value, net photosynthetic rate, transpiration rate and stomatal conduction degree day of maize increased first and then decreased,and N16 treatment was the highest,and intercellular carbon dioxide concentration was the lowest.The changes of net photosynthetic rate,transpiration rate and stomatal conduction degree day showed unimodal curve.The light response curve fitting analysis showed that the maximum net photosynthetic rate of N16 treatment was the highest.In 2019 and 2020,N16 treatments were 37.48%,29.51%,31.85%,18.17%,37.32% and 80.04%,59.73%,50.30%,6.42%,62.51% higher than N0,N8,N12,N20 and N24 treatments,respectively.Dry matter mass accumulation in whole plant and ear were positively correlated with maximum net photosynthetic rate,apparent quantum efficiency and SPAD value.Comprehensive analysis showed that the most suitable nitrogen fertilizer application rate in western Inner Mongolia was 240 kg/ha.

In order to study the effect of applying N,P and K fertilizer on the yield and nutrient use efficiency of oil sunflower under the double cropping pattern of winter wheat-summer oil sunflower in Southern Shanxi,a field plot fertilizer experiment was carried out with Linkui 4 from 2019 to 2021.Four fertilization treatments including NPK,PK,NK and NP were set up.The effects of different fertilization treatments on yield response,agronomic efficiency and fertilizer use efficiency of N,P,K were analyzed.The results showed that the three-year average yield of oil sunflower treated with NPK was 3 634 kg/ha(3 502—3 818 kg/ha),which was 19.6%,12.1%,13.7% higher than that of PK/NK/NP,respectively.PK treatment had the lowest yield.The average yield responses of N,P and K fertilizers were 588.8(481.0—704.7 kg/ha),391.8(296.0—488.7 kg/ha),438.2 kg/ha(329.3—629.7 kg/ha),respectively.The agronomic efficiencies of N,P and K were 3.8(2.8—4.9 kg/kg),3.1(2.1—4.1 kg/kg),2.9 kg/kg(2.2—4.2 kg/kg),respectively.The aboveground accumulations of N,P and K were 174.4(172.5—176.8 kg/ha),60.0(58.3—61.8 kg/ha),241.1 kg/ha(236.2—246.8 kg/ha),respectively.The nutrient use efficiency of N,P,K was 36.3%(36.0%—36.7%),15.7%(15.3%—16.2%)and 47.1%(46.0%—47.9%),respectively,of which K>N>P.So the application of N,P and K fertilizer could not only significantly increase the oil sunflower yield but also the aboveground accumulation of N,P and K.Among the three kinds of NPK fertilizers,N increased the yield most,and K uptake by the aboveground part and utilization rate of oil sunflower was the highest.Therefore,in the production we should pay attention to the reasonable application of N,P and K,while N and K should be supplemented by seed fertilizer and topdressing.

In order to study the differences in yield and nitrogen utilization,transport and accumulation of different winter wheat cultivar(line)types in the Northern Huanghuai,the yield traits and nitrogen utilization efficiency of 29 and 26 winter wheat cultivars(lines)for testing in the Northern Huanghuai wheat area were investigated and analyzed in 2021—2022 and 2022—2023,respectively.Through cluster analysis,wheat was classified into four types:high-yielding,medium-high-yielding,medium-yielding and low-yielding.Nitrogen content of wheat stems,leaves,spikes,and grains at maturity were measured at anthesis and maturity,respectively,to analyze the relationship between parameters related to nitrogen utilization traits and yield.The results showed that the average yields among high-yielding,medium-high-yielding,medium-yielding and low-yielding varieties(lines)differed significantly from 2021 to 2023,with the number of spikes per hectare of high-yielding varieties significantly higher than that of other types.At the anthesis stage,the nitrogen accumulation and distribution rate of each organ were stems and sheaths>leaves>spikes;at the maturity stage,the nitrogen accumulation of each organ was grains>stems and sheaths>spikes>leaves.The post-anthesis nitrogen accumulation,pre-anthesis nitrogen transport and its contribution to the grain of different varieties of wheat were higher in high-yielding varieties(lines),and the pre-anthesis nitrogen transport and its contribution to the grain were greater than the post-anthesis nitrogen accumulation and its contribution to the grain.Nitrogen utilization efficiency,nitrogen harvest index,nitrogen accumulation at anthesis and nitrogen accumulation at maturity were significantly and positively correlated with wheat grain yield.Therefore,water and fertilizer management can be carried out through the nitrogen uptake and transfer pattern and distribution characteristics of different varieties,or selecting and breeding wheat varieties with high nitrogen utilization efficiency to achieve high-yield and high-efficiency production of wheat.

In order to provide theoretical basis for straw fertilizing high-yield field and improving saline-alkali field in the process of continuous high yield and stable yield of spring corn in Inner Mongolia plain irrigation area.This study set up a positioning test of corn straw returning to the field for 1 to 4 years (HT1—HT4), taking the straw not returning to the field as the control (CK). Soil organic carbon content, total nitrogen content, available nitrogen content, available phosphorus content, cation exchange capacity, pH value and acid-base buffer curve were measured before spring sowing and during harvest. The results showed that, the relative change rates of soil organic carbon content, total nitrogen content, available nitrogen content, available phosphorus content and cation exchange capacity were 1.34%—3.62%, 0.20%—1.51%, -0.11%—0.78%, 0.89%—6.36% and 0.09%—0.41% during harvest period of HT1—HT4 compared with that before spring sowing. The relative change rates of soil organic carbon content, total nitrogen content, available nitrogen content, available phosphorus content and cation exchange capacity were 1.57%, -0.02%, -0.45%, -0.15% and -0.05% in CK harvest period compared with that before spring sowing. Soil pH value of HT2, HT3 and HT4 was significantly lower than that of CK. The buffer capacity of soil to alkali was HT4>HT3>HT2>HT1>CK. In summary, with the increase of straw returning years, soil carbon sequestration capacity, fertilizer retention capacity and buffering performance increase, and the ability to effectively resist drastic changes in soil pH value caused by fertilizer application and other factors was enhanced, soil quality was significantly improved by straw returning to field for fertilizer cultivation and soil improvement measures.

In order to explore the suitable phosphate fertilizer application methods in the Huang-Huai area,this research conducted field experiments to investigate the dry matter accumulation,root morphological indexes,available phosphorus content and phosphatase activity in different soil layers,maize yield and its component factors of four phosphate fertilizer application methods(conventional broadcast (P1),layered application (P2),strip application (P3) and hole application (P4)).The results showed that the ear length and kernel row number of P2 and P4 were significantly increased by 22.57%,16.81% and 15.19%,7.60% compared with P1.The grain number per spike of P2,P3 and P4 were significantly increased by 25.26%,13.86% and 17.00% compared with P1,respectively.Additionally,a decrease of spikes per area was found in P2 (15.30%) compared with P1.The yields of P2 and P4 were significantly increased by 15.20% and 10.79% compared with P1.Among root traits,the root length,root surface area,root volume and root tip number were significantly affected by the phosphorus application method.The root length under P2 and P4 treatments was significantly increased by 30.41% and 33.75% compared with P1.The root surface area of P2 treatment was significantly increased by 23.77% compared with P1.The root surface area of P4 treatment was significantly increased by 29.60% and 21.70% compared with P1 and P3 treatments,respectively.The root volume and root tip number of P2 and P4 treatments were significantly higher than those of P1 and P3.The analysis of soil available phosphorus content showed that the available phosphorus contents of P2 and P4 were significantly higher than that of P1 in the soil layer of 10—20 cm at three-leaf stage of maize.The available phosphorus contents of P2,P3 and P4 in the 0—20 cm soil layer were lower than that of P1,and the available phosphorus content of P4 in the soil layer of 20—30 cm was significantly lower than that of P1 at maturity stage.Correlation analysis showed that there was a significant positive correlation between acid phosphatase activity and soil available phosphorus content in the 10—20 cm soil layer at three-leaf stage of maize.The acid phosphatase activity and soil available phosphorus content in P2 and P4 treatments were higher in this soil layer,which was conducive to the conversion of soil phosphorus into maize absorbable state.In conclusion,compared with the traditional application method,layered phosphorus application and cave phosphorus application can improve the soil phosphorus availability in the early stage of maize,promote the growth and development of roots,and then increase the summer maize yield,so they are more suitable application method for corn phosphorus fertilizer in Huang-Huai area.

Partial substitution of organic fertilizer nitrogen for chemical fertilizer nitrogen is one of the ways to achieve sustainable crop development.This study explored the appropriate ratio of wheat organic nitrogen partial substitution for chemical nitrogen,as well as the characteristics of nitrogen accumulation,transportation,and utilization after substitution,in order to provide a basis for nitrogen fertilizer reduction and efficiency enhancement technology for winter wheat in Hebei Region.Field experiments of the following nine treatments were conducted in Ningjin,Hebei from 2021 to 2023:T1,non-nitrogen,and application of chemical P and K fertilizer alone;T2,high efficiency fertilization treatment,and application of chemical N,P and K fertilizer alone;T3—T7,substitution of 20%,40%,60%,80% and 100% the chemical N rate of T2 with organic fertilizer,respectively;T8,traditional fertilization,and application of chemical N,P and K fertilizer alone;T9,substitution of 100% chemical N rate of T2 with organic fertilizer,and spraying liquid nitrogen fertilizer at the erecting stage.The results of two years of experiments showed that the 100% substitution rate+liquid nitrogen treatment could achieve the highest wheat yield.Secondly,the yield of the 40% substitution rate treatment was equivalent to that of the high efficiency fertilization treatment,and it was much higher than that of the traditional fertilization treatment in the second year of the experiment.The 100% substitution rate+liquid nitrogen treatment increased the nitrogen content in stems and leaves by spraying available nitrogen during the erecting period,and the nitrogen accumulation in plants was equivalent to that of high efficiency fertilization and traditional fertilization treatments.Treatment with 40% and 80% substitution rates also achieved nitrogen accumulation equivalent to the highly efficient fertilization treatment.The 20%—100% substitution rate treatment (including liquid nitrogen treatment) could achieve a higher nitrogen transfer rate in stems and leaves,as well as the contribution rate of nitrogen transfer to grain.Among them,the 100% substitution rate+liquid nitrogen treatment had good fertilizer nitrogen absorption and utilization effect,achieving higher fertilizer nitrogen accumulation,nitrogen utilization rate,and nitrogen harvest index.Nitrogen fertilizer effect of the 100% substitution rate+liquid nitrogen treatment was equivalent to or slightly higher than that of highly efficient fertilization treatment.Secondly,the treatment with the 40% substitution rate had a similar or slightly lower nitrogen fertilizer effect than the highly efficient fertilization treatment.In summary,the 100% substitution rate+liquid nitrogen treatment showed better wheat yield,plant nitrogen accumulation,nitrogen transport rate,grain nitrogen accumulation,and nitrogen efficiency,followed by the 40% substitution rate treatment.

To investigate the influence of green manure cultivation on the carbon and nitrogen content of saline-alkali soil under freshwater leaching,a field experiment was conducted from October 2021 to May 2022.Three treatments were set up:winter fallow(T1),Dongmu 70 rye(T2),and rape(T3).The spatial distribution of soil organic carbon(SOC),nitrate nitrogen($\mathrm{NO}_{3}{ }^{-}-\mathrm{N}$),and ammonium nitrogen($\mathrm{NH}_{4}^{+}-\mathrm{N}$)in the soil and leachate were measured.The results revealed that in the 0—30 cm soil layer,the soil organic carbon content of T1,T2,and T3 increased from 6.20,6.58,7.24 g/kg before leaching to 6.48,7.39,8.06 g/kg after leaching,representing an increase of 4.41%,12.20%,and 11.23%,respectively.After freshwater leaching,the nitrate nitrogen content in the 0—60 cm soil layer of T1 was significantly higher than that of T2 and T3.In the 0—30 cm soil layer,the respective reductions for each treatment were 42.42%,3.85%,and 10.84%.In the 60—90 cm soil layer,the reductions were 1.38%,7.96% and 18.11%.There were no significant differences in ammonium nitrogen content among the different treatments before leaching,but after leaching,the highest ammonium nitrogen content was observed in T2.In conclusion,after leaching irrigation,the soil organic carbon content in different soil layers increased compared to before leaching,while soil nitrogen showed a significant decrease.Analysis of nitrogen content in the soil and leachate indicated that the main nitrogen loss caused by leaching irrigation was in the form of nitrate nitrogen.Compared to winter fallow farmland,the cultivation of rapeseed green manure had a significant effect on increasing soil nitrogen content,while Dongmu 70 green manure was the the most effective in reducing soil nitrogen loss.

In order to solve the problems of non-point source pollution caused by a large amount of nitrogen loss in the early growth stage and insufficient nitrogen supply in the late growth stage of dry land millet in Ningxia,which led to premature senescence and yield reduction.Under the nitrogen application rate of 135 kg/ha,five nitrogen treatments were designed according to the ratio of base fertilizer∶jointing fertilizer∶ear fertilizer.The ratio of base fertilizer∶jointing fertilizer∶ear fertilizer was 6∶2∶2(N1,nitrogen fertilizer was in front),6∶0∶4(N2,conventional nitrogen management),2∶4∶4(N3,the front nitrogen moves backward),4∶6∶0(N4,front nitrogen moved back),4∶0∶6(N5,nitrogen from front to back),no nitrogen fertilizer treatment(CK).The effects of nitrogen fertilizer backward movement on dry matter accumulation,grain yield and nitrogen absorption and utilization efficiency of broomcorn millet were studied.The purpose of this paper was to explore the best nitrogen application period and amount of broomcorn millet.The effects of nitrogen application on dry matter accumulation,grain yield and its components,and nitrogen use efficiency of broomcorn millet in different growth stages were significantly different,and all of them were significantly higher than CK.The effects on grain yield and its components of broomcorn millet were significantly higher than that of CK,and the grain yield of each treatment increased 18.9%,26.6%,30.8%,22.1% and 23.3% compared with CK,respectively.Nitrogen accumulation of each treatment showed spike>stems>leaf>root,and significantly higher than CK.N use efficiency was significantly higher than CK,and N backward treatment(N3,N4,N5)increased by 4.75,3.08 and 2.99 percent points,respectively,compared with nitrogen pre-treatment(N1).Based on principal component analysis and correlation analysis,N3(base fertilizer∶jointing fertilizer∶heading fertilizer ratio of 2∶4∶4)was the best plan for the backward transfer of nitrogen fertilizer in broomcorn millet production in the mountainous area of Southern Ningxia.The appropriate delayed nitrogen transfer could promote the accumulation and transport of dry matter and nitrogen,improve the nitrogen metabolism of broomcorn millet leaves at the late growth stage,delay leaf senescence,and improve the yield of broomcorn millet.

Define the cultivation measures of long-leaf tobacco seedlings in tobacco-rice rotation area to promote the early growth and rapid development of paddy-tobacco.Yunyan 87 was used as the material.The effects of three factors on dry matter and nutrient accumulation and distribution,and fertilizer use efficiency of flue-cured tobacco were studied,namely,the aperture of nursery site(136,200 pores),microbial agent(substrate with Miaoqiangzhuang microbial agent,substrate without microbial agent),and transplanting leaf age(8-leaf transplanting,10-leaf transplanting).The results showed that increasing the aperture of nursery site and adding microbial agent in the substrate to cultivate long-leaf tobacco seedlings could increase dry matter accumulation,improve dry matter distribution,increase nitrogen,phosphorus and potassium accumulation,promote fertilizer absorption efficiency,and increase fertilizer utilization rate and production efficiency;the contribution rates of aperture of nursery site,microbial agent,transplanting leaf age and the interaction of three factors to dry matter accumulation were 22.87%,27.73%,37.41% and 11.99%,respectively.The contribution rates to nitrogen accumulation were 20.34%,23.45%,33.62% and 22.59%,respectively.The contribution rates of phosphorus accumulation were 24.41%,27.81%,32.85% and 14.93%,respectively.The contribution rates of potassium accumulation were 15.48%,26.05%,34.61% and 23.86%,respectively.The contribution rates to nitrogen efficiency were 20.81%,44.67%,23.11% and 11.41%,respectively.The contribution rates of phosphorus fertilizer efficiency were 32.15%,31.66%,14.91% and 21.28%,respectively.The contribution rates of potassium fertilizer efficiency were 25.31%,38.71%,31.67% and 4.31%,respectively.In Hunan paddy-tobacco growing area,increasing the aperture of nursery site and adding microbial agents to the substrate can make up for the defects of two-stage seedling raising,and jointly improve nutrient uptake and fertilizer utilization efficiency,which has a certain popularization value in flue-cured tobacco production.

Using tomato as experimental material and using sand cultivation method,the effects of exogenous addition of potassium humate and amino acid fertilizer on the metabolic pathway,plant biomass,nutrient uptake,yield and quality index of tomato at seedling stage were explored.The experimental results showed that:the root growth of tomato increased by 118% and 13% at the seedling stage and flowering and fruiting stage under potassium humate treatment,and the nitrogen,phosphorus and potassium carrying in the stem increased significantly by 31%,45% and 26%.The amount of phosphorus carried out in leaves increased significantly by 92%.Phosphorus carrying from fruit also increased significantly by 45%.The metabolomic results showed that potassium humate treatment mainly affected tomato glutathione metabolism,glycine serine and threonine metabolism,porphyrin and chlorophyll metabolism,while amino acid fertilizer treatment mainly affected tomato propionic acid metabolism,pantothenic acid and coenzyme A biosynthesis and TCA cycling.Compared with the blank control,the yield of tomatoes under potassium humate treatment increased by 35%,the fresh weight and dry weight of the aboveground increased by 21% and 5%,and the soluble sugar content,sugar-acid ratio and soluble solids content in tomato fruits were also significantly increased,with increases of 30%,41% and 0.39 percentage point,respectively.The application of amino acid fertilizer significantly increased the root length,aerial fresh weight and fruit yield of tomato during the flowering and fruiting stage,which increased by 19%,18% and 26%,respectively,and the soluble solids content of tomato fruit increased by 0.30 percentage point,the solid-acid ratio increased by 16%,and the weight per fruit increased by 15.6%.In summary,the application of potassium humate and amino acid fertilizer can significantly change the carbon and nitrogen metabolism process of sand tomato plants,promote tomato growth and fruit quality,and is an effective agronomic measure to achieve high-yield and high-quality tomato cultivation.

In order to explore the effect of applying biochar on the improvement of soil physical and chemical properties in pear orchards and the continuous impact on the fruit quality of Huangguan pear,the positioning experiments for four consecutive years were conducted to provide theories and technologies support for rational and efficient fertilization in Huangguan pear orchards in Hebei Province.The experiment was carried out in the Huangguan pear experimental base in Jinzhou City,Hebei Province.Taking the treatment without biochar as the control(CK),the application of 0.45(B1),0.90(B2),1.35(B3),1.80 kg/m²(B4)4 treatments were used to study the effects of different amounts of biochar on soil organic matter,nitrate nitrogen,available phosphorus,available potassium,electrical conductivity and pH,and explored the effects on fruit quality(such as total soluble sugar,titratable acid,firmness,soluble solids,and single fruit weight)of Huangguan pear during ripening.The application of biochar for four consecutive years significantly reduced the soil nitrate nitrogen content,and increased the contents of organic matter,available phosphorus,available potassium and pH in the surface layer(0-20 cm),and the effect on the surface layer(0-20 cm)was greater than that in the 20-40 cm soil layer.B3 treatment had the best improvement effect on soil nutrients.The influence of soluble solid content on the fruit quality of Huangguan pear showed an increasing trend,and titrable acid showed a decreasing trend.There was no significant difference between B2 and B3 treatments on the quality of Huangguan pear.Considering the long-term cumulative effect of soil and the economic cost of biochar,0.90-1.35 kg/m² biochar application rate was recommended as the appropriate application rate.Combined with the analysis of the effects of the amount of biochar on the soil physicochemical properties and pear quality,under this test condition the recommended amount of biochar was 0.90 kg/m².

To reveal the soil factors that formed the quality characteristics of Hebei chestnut,54 typical chestnut orchards from 8 counties in Hebei Province were selected as the objects,and the contents of 9 mineral elements in the soil were studied by using significance,correlation and principal component analysis.The results showed that there were no significant differences in contents of Mg and Na,but there were significant differences in N,P,K,Ca,Fe,Mn and Cu contents in the soil of chestnut plantations in the main chest nut production areas.The N content in the soil of chestnut orchards was generally below the level of 3,and the P content was generally above the level of 3.The K content was generally at a low level,which was below the level of 5.The correlation of the contents of metal elements such as Ca,Mg,Fe,Mn,Cu and Na were significantly correlated with each other in soil.They were also significantly correlated with P element,and the correlation with N content was generally weak.Principal component analysis showed that mineral elements in the first 3 principal components reflect the total information content 73.521%.The contribution rate of the first principal component accounted for 44.678%,and the elements which included Ca(0.871),Cu(0.840),Fe(0.809)and Mg(0.806)were the main factors.It showed that the metal trace element content contributes more to the principal component.The comprehensive score was based on the mineral elements content of different chestnut orchards,which decided the order of high and low.The highest score was in Qianxi County(0.591 8).The ranking of the soil quality in the main chest nut production areas was:Qianxi>Qinglong>Xinglong>Kuancheng>Shahe>Zunhua>Xindu>Funing.To sum up,it is confirmed that the comprehensive scores of metal elements contents such as Ca,Mg,Fe,Cu can be used to evaluate the soil quality by using principal component analysis.It was advisable to select high K and low P compound fertilizer,and it was recommended to apply multiple elements mixed fertilization as a supplementary measure to improve the soil quality level of chestnut orchards.

The effects of long-term manure application on water-dispersible phosphorus (P)content and morphological distribution in three zonal soils were explored to provide references for understanding the risk assessment of P loss. The soil samples were collected from the farmland in Daxing Beijing(Fluvo-aquic soils),Yueyang Hunan(Red earths)and Zhanjiang Guangdong(Humid-thermo ferralitic)from May 2021 to August 2021,the sample was a composite mix of five individual surface soil cores (0—20 cm). The characteristics of water-dispersible P,morphological distribution,and minerals contents were studied. Compared with the treatment without manure application,the water-dispersible P content of the three zonal soils in Daxing,Yueyang and Zhanjiang was significantly increased by 1.15,1.32,14.00 times,respectively. Long-term application of manure significantly changed the distribution ratio of different forms of water-dispersible P in the total soil water-dispersible P,and the proportion of particulate P in Daxing and Yueyang soils decreased significantly by 30.22 and 14.68 percentage points,respectively,while the proportion of dissolved P significantly increased by 29.83 and 28.06 percentage points,respectively. The proportion of colloidal P in Yueyang soil significantly decreased by 13.37 percentage,and the proportion of dissolved P in Zhanjiang soil with long-term manure application significantly increased by 8.24 percentage points,compared with the soils without manure application. Long-term manure application remarkablely changed the content of soil water-dispersible minerals. Compared to the control group without manure application, the content of water-dispersible calcium in Daxing, Yueyang, and Zhanjiang soils increased significantly by 0.55, 1.66, and 4.15 times, respectively. The water-dispersible magnesium content also significantly increased by 0.66, 1.46, and 8.39 times in these soils. Additionally, the water-dispersible aluminum content in Daxing soil increased by 9.09%, while it decreased significantly by 19.90% and 77.27% in Yueyang and Zhanjiang soils, respectively.The results of redundancy analysis showed that soil pH,cation exchange capacity (CEC), dissolved organic carbon (DOC),and water-dispersible mineral composition (Fe/Al/Ca/Mg)were the main predictors affecting soil water-dispersible P content and morphological distribution. Long-term manure application significantly increased the water-dispersible P content of the three zonal soils and affected the P transformation,which aggravated the risk of P loss. Long-term manure application favored the particulate P and colloidal P of Yueyang and Zhanjiang soils and the particulate P of Daxing soil transformed to the dissolved P. Therefore,long-term manure application mainly affects the water dispersible P forms by changing the transformation between particulate P and dissolved P.

To explore the effects of long-term multi-cropping patterns on soil structure and organic carbon distribution in paddy fields. With fallow-rice-rice (WF-R-R) model as the control, four multi-cropping models were set up: rape-rice-ric (RP-R-R), Chinese milk vetch-rice-rice (MV-R-R), Potato-rice-rice (PO-R-R), ryegrass-rice-rice (RG-R-R). The results showed that in 5—10 cm soil layer, the contents of water-stable aggregates with size of >2 mm were increased in the multi-cropping pattern. The RG-R-R mode was 11.26 percentage points higher than the control, and the mean weight diameter (MWD) was significantly higher than the control. In 0—5 cm soil layer, the organic carbon content was increased by multi-cropping mode. The SOC content in RG-R-R mode was the highest in 0—20 cm soil layer, and the SOC content in each soil layer was increased by 9.57% (0—5 cm), 4.45% (5—10 cm) and 5.96% (10—20 cm), respectively, compared with the control. With the deepening of soil layer and the decrease of aggregate particle size, the soil organic carbon content in the multi-cropping model increased more significantly than that in the control. When the size was <0.053 mm, the soil organic carbon content in the RG-R-R model was significantly higher than that in the control. The contribution rate of soil aggregate organic carbon mainly came from the >2 mm grain size (59.03%—79.33%). In the 5—10 cm soil layer, the contribution rate of aggregate carbon in the >2 mm size of MV-R-R, PO-R-R and RG-R-R models was significantly increased by 8.5, 7.18 and 14.65 percentage points compared with the control. In conclusion, in this study, the ryegrass-rice-rice (RG-R-R) model was conducive to soil aggregate stability and organic carbon fixation in southern paddy fields.