In this research,a field orientation experiment on sorghum-maize rotation was conducted.The effects of different fertilization conditions on the growth,nutrient,soil enzyme activity and microbial activity of sorghum was studied.The experimental results showed that different fertilizer could significantly increase the jointing stage of sorghum plant height,stem diameter,number of pieces and index pages visible leaf area,as well as sorghum yield and grain weight per spike (P<0.05).Each processing production order of IF+M+S > IF+M > M+S > IF > CK,compared to the control,the range of yield increase of sorghum in different fertilization levels were 80.6%-120.7%,respectively,reaching a significant level,and among which IF+M+S treatment was the best.All values of inorganic fertilizer treatments were slightly higher than that of no fertilization treatment. The organic fertilizer treatment increased the soil nutrients and organic matter content of sorghum, compared with the inorganic fertilizer treatment. The total N, available P, available K, organic matter of IF+M+S treatment were 1.95, 10.36, 2.01, 1.83 times of CK, respectively (P<0.05). Soil enzyme activity of fertilization treatments in different growth periods was higher than no fertilization (CK),in which the most was the treatment of IF+M+S,activity of alkaline phosphatase in jointing stage and harvest stage,urease in harvest stage,invertase in jointing stage,flowering stage and harvest stage were all significantly higher than that of inorganic fertilizer treatment (P<0.05).The application of organic fertilizer or application combined with inorganic fertilizer could improve the soil microbial community functional diversity and the capability of utilizing carbon sources.And the treatments containing organic fertilizer and straw manure were more conducive to improve soil microbial diversity than other organic fertilizer treatments.

In order to study the physiological response and difference of nitrogen metabolizing enzyme activity in leaves of different forage oats in Horqin Sandy Land. The forage oats of Muwang and Tianyan No.1 were applied with 0 (CK), 100, 200, 300 kg/ha pure nitrogen in the proportion of 15%, 40%, 25% and 20% at tillering, jointing, heading and flowering stages. The activities of glutamate synthase (GOGAT), glutamine synthetase (GS), nitrate reductase (NR), glutamic oxaloacetic transaminase (GOT), glutamic pyruvate transaminase (GPT) were measured in flag leaf, inverted two leaf and converse third leaf during the filling period, and the differences of nitrogen metabolizing enzyme activities and their relationship with hay yield of different forage oat varieties under nitrogen application rate were analyzed. The results showed that the hay yield of Muwang and Tianyan No.1 reached the maximum at 200,300 kg/ha nitrogen levels, respectively;The activities of GOGAT, GS, NR, GOT and GPT in the leaves of Muwang and Tianyan No.1 forage oats increased first and then decreased with the increase of nitrogen application, and the enzyme activity was the strongest under N₂₀₀ nitrogen application (except for GOT activity of converse third leaf under N₃₀₀ treatment).Except for GS activity of the third leaf of N₁₀₀ treatment and GPT activity of the second leaf in different nitrogen treatments, GOGAT, NR, GS, GOT and GPT enzyme activities of Muwang were higher than those of Tianyan No.1. This indicated that nitrogen assimilation ability of forage oat variety Muwang was stronger than that of Tianyan No.1.Therefore, in Horqin Sandy Land, the suitable amount of topdressing nitrogen fertilizer for planting Muwang was 200 kg/ha, while for planting Tianyan No.1, topdressing nitrogen fertilizer of 300 kg/ha could obtain higher hay yield. GOT and GPT activities were the key enzymes for screening forage oat varieties with high nitrogen use efficiency.

In order to clarify the change rule of photosynthetic characteristics and the best fertilization method in different growth stages of sweet sorghum under different fertilization treatments, the field experiment was conducted to study the stomatal conductance (Gs), intercellular CO₂ concentration (Ci), transpiration rate (Tr), net photosynthetic rate (Pn), chlorophyll (SPAD), water use efficiency (WUE) and yield of New Sorghum No.3 under 8 different fertilization treatments, including CK, NK, NP, PK, NPK, M (organic fertilizer), NPKM and 1.5NPKM.The results showed that the changes of Pn, Gs, WUE and SPAD value in sorghum leaves under different fertilization treatments were the same at different growth stages, showing a trend of first increasing and then decreasing, and peaking at grain filling stage. The variation trend of Tr and Ci from flowering stage to maturity stage decreased first and then increased, and reached the lowest value in grain filling stage. At the same growth stage, the photosynthetic characteristics of different fertilization treatments were different, and the photosynthetic characteristics of leaves were affected by fertilization treatments. The Tr, Gs and Ci values of NPKM fertilization treatment at maturity stage were higher than those of other treatments, which were 3.64 mmol/(m²·s),328 mmol/(m²·s),439 μmol/mol, respectively. The correlation analysis showed that Pn of NPKM treatment at flowering stage was significant positively correlated with Tr and WUE, while Pn of NPK treatment was positively correlated with Gs and Ci. The biological yield of all fertilization treatments was significantly higher than CK, among them the biological yield of NPKM treatment reached 94.81 t/ha. The biological yield of NPKM increased 97.95%, 26.65%, 20.24%, 19.57%, 15.16%,14.98% and 11.74% respectively compared with CK, M, 1.5 NPKM, NK, PK, NPK and NP. Fertilization affects the photosynthetic parameters of the leaves of New Sorghum No.3 and was conducive to increasing yield. Therefore, it is feasible to use high photosynthetic efficiency breeding to improve biological yield. In order to alleviate the obstacle of continuous cropping of sweet sorghum, different proportion of fertilizer should be adopted. In a word, NPKM is the best fertilization mode to improve photosynthetic conditions and maximize yield, so it is preliminarily confirmed that NPKM is the best fertilization mode to promote the growth and development of continuous cropping sorghum in arid area.

Based on the long-term located fertilization experiment of Laiyang, Shandong Province, China, began in 1978, to study the transport and accumulation characteristics of nitrate nitrogen and ammonium nitrogen in the Fluvo-aquic soil and its relationship with the summer maize yield.The test set organic fertilizer(M), nitrogen fertilizer(N)2 factors, 3 levels, 9 treatment;3 levels of organic fertilizer(M):M₀(0 t/ha), M₁(30 t/ha), M₂(60 t/ha), and 3 levels of nitrogen fertilizer(N):N₀(0 kg/ha), N₁(138 kg/ha), N₂(276 kg/ha).After summer corn harvest in 2014 and 2015, the contents of nitrate nitrogen and ammonium nitrogen in soil 0-20, 20-40, 40-60, 60-80 and 80-100 cm were measured respectively, the accumulation of nitrate nitrogen, ammonium nitrogen in different soil depth of 0-100 cm and the summer corn yield were calculated.The results showed that the amount of nitrate nitrogen, ammonium nitrogen and its accumulation amount in soil could be improved by applying organic fertilizer or nitrogen fertilizer.In the 0-100 cm soil layer, the vertical migration trends of nitrate nitrogen of different treatments were different, but the vertical migration trend of ammonium nitrogen were basically the same.Compared with chemical fertilizer, application of organic fertilizer could slow nitrate to the deep soil leaching, but both of ammonium nitrogen to influence the trend of migration in deep soil was not obvious.Long-term application of organic fertilizer, nitrogen fertilizer on nitrate nitrogen, ammonium nitrogen accumulation amount of the impact of extremely significant level, there was extremely significant interaction effect on the accumulation of nitrate nitrogen in soil.Compared with the M₀N₀(CK), the accumulation of nitrate nitrogen and ammonium nitrogen in the addition of fertilization treatments were significantly respectively increased by 112%-396% and 69%-259% at P<0.05.In 0-20, 0-40, 0-60, 0-80, 0-100 cm in each soil layer, the nitrate nitrogen accumulation and the ammonium nitrogen accumulation had different linear relationship with summer maize yield.Research showed that rational application of organic and inorganic fertilizers could reduce the accumulation of nitrate nitrogen and ammonium nitrogen in soil and the leaching, and it is advantageous to improve the yield of crops, maintain the stability of the soil ecosystem, promote the sustainable development of agriculture and protect the groundwater resources.

In order to research the influences of nitrogen reduction combined with soil conditioners on the growth and Cd uptake of rice to provide a scientific basis for Cd pollution paddy field used safely and fertilization reasonably.A field experiment was conducted to investigate the influences of nitrogen reduction combined with the alkaline slow-release fertilize,organic fertilizer and microbial fertilizer on the rice yields and Cd contents in the Cd contaminated paddy soil.The results showed that the rice yields increased by 7.42%(P<0.05), 8.59%(P<0.05) and 4.59% than the contrast with the application of alkaline slow-release fertilize, organic fertilizer and microbial fertilizer respectively. And the rice yields increased by 5.55% and 7.61%(P<0.05),respectively,of the nitrogen reduction 20% combined with alkaline slow-release fertilizer and organic fertilizer,but the nitrogen reduction 20% with microbial fertilizer decreased the production by 2.48%.So the results suggested that it was feasible to reduce the N fertilizer under this experiment condition.Both the alkaline slow-release fertilizer applied alone or combined with nitrogen reduction 20% could increase the soil pH effectively and decrease the soil available Cd content,and reduced the Cd contents of rice stem and grain efficiently with 31.29% (P<0.05) and 26.58% (P<0.05) than the contrast.Applying of organic fertilizer also increased the soil pH value and reduced the soil available Cd content effectively,and reduced the Cd contents of stem and rice obviously,but there was no evident effect of decreasing of Cd contents in stem and rice when organic fertilizer combined with nitrogen reduction 20%,the Cd content of rice lowered by 31.27%(P<0.05) and 11.96% compared to the contrast when applied organic fertilizer alone and with nitrogen reduction 20%.And the Cd contents of stem and rice had no significant differences compared to the contrast both applied microbial fertilizer alone and with nitrogen reduction 20%.The effect on decreasing Cd content of stem and rice weakened when nitrogen reduction 20% combined with alkaline slow-release fertilizer and organic fertilizer and microbial fertilizer.Overall consideration of the rice yields and the Cd reduction effects of rice and stem,nitrogen reduction 20% combined with alkaline slow-release fertilizer could enhance rice yield as well as reduce Cd content in rice stem and rice,which was applicable for rice production in Cd contaminated paddy soil.

In order to improve the nitrogen use efficiency and corn yield during the whole growth period of maize, it provides a reference for the high-yield nitrogen fertilizer operation model of maize in Heilongjiang Area. Ratio (CK:blank control; T1:50% base fertilizer+50% flowering fertilizer; T2:30% base fertilizer+40% jointing fertilizer+30% flowering fertilizer; T3:20% base fertilizer+60% jointing fertilizer+20% flowering fertilizer; T4:10% basal fertilizer+60% jointing fertilizer+30% flowering fertilizer) on the change of soil inorganic nitrogen content, nitrogen balance, nitrogen accumulation at different growth stages, nitrogen use efficiency and corn yield. The results showed that compared with the control group, T2, T3, and T4 effectively increased the inorganic nitrogen content of the soil plow layer during the filling stage and the mature stage; in terms of nitrogen balance, T2, T3, and T4 were significant difference than the T1 treatment. Reduced the apparent nitrogen loss, of which T4 apparent nitrogen loss was the lowest; compared with T1, reducing the ratio of nitrogen to topdressing significantly increased the nitrogen accumulation during the flowering-maturity period, and the nitrogen accumulation during the filling-maturity period T4 was the highest treatment; compared with T1, T2, T3, and T4 significantly increased the nitrogen absorption and utilization rate, agronomic utilization rate and partial productivity of maize, and the increase ranges was 16.66%-22.47%, 17.80%-35.76%, 4.93%-9.90% (Xianyu 335) and 6.55%-24.46%, 8.23%-36.94%, 2.02%-5.44% (Tiannong 9); reducing the ratio of nitrogen fertilizer to topdressing (T2, T3, T4) yields significantly higher than the traditional nitrogen application treatment T1, T3 had the highest yield, which was 9.90% (Xianyu 335) and 8.86% (Tiannong 9) compared with T1. In summary, under the experimental conditions, when the total nitrogen application rate was 210 kg/ha, 20% basal fertilizer+60% jointing fertilizer+20% flowering fertilizer was the best nitrogen basal dressing ratio.

In order to study the effects of loss control and ordinary fertilizers on nutrient accumulation and growth and development of summer maize,field experiments were conducted at the Xinji experimental station of Agricultural University of Hebei during 2014-2015.Maize morphology and physiology characters and nutrient uptake efficiency were studied using maize hybrid Zhengdan 958 as material.The results showed that with the same nutrient amount (N 144 kg/ha,P₂O₅ 72 kg/ha,K₂O 72 kg/ha) of loss control and ordinary fertilizer applied,there were significant changes on maize growth and development,dry matter accumulation and nutrient accumulation,and the effects of loss control fertilizer treatment were significantly better than those of ordinary fertilizer.Compared with ordinary fertilizer,the 1 000 grains weight,dry matter and yield of maize of loss control fertilizer could be increased by 12.3%,12.8% and 6.9%,respectively.The content of nutrient elements in organs of loss control fertilizer treatment was higher than that of the ordinary fertilizer.Maize leaf area index and photosynthetic rate at kernel filling stage were enhanced by loss control fertilizer treatment.Stalk thickness and puncture resistance of basal internodes of loss control fertilizer treatment maize were also enhanced,so the lodging resistance ability was increased.As a new type of fertilizer,loss control fertilizer would play an important role in improving the yield of maize,increasing the efficiency of fertilization and protecting the environment.

In order to explore the effects of nutrient expert (NE) management on nitrogen (N) use efficiency and soil organic carbon (SOC) sequestration in the wheat-maize rotation system and improve its management practices, a long-term experiment was set up in 2009 to compare NE management with farmer's practice (FP) management. Through 9-years experiment, the crop yield, N use efficiency, SOC content, SOC sequestration rate and SOC sequestration efficiency were measured and analyzed. The advantages of long-term NE management in wheat-maize crop rotation system were evaluated. The results showed that long-term NE management reduced the amount of N fertilizer application rate, compared with FP management, but maintained the crop yields (no significant difference with FP). Compared with FP management, the average accumulative recovery efficiency of N, agronomic efficiency of N, and partial productivity of N in NE management system increased by 7.4 percentage points, 39.7%, and 28.4% in maize production system, and increased by 8.0 percentage points, 28.9%, and 32.8% in wheat production system, respectively After 9-years experiment, both NE and FP increased the SOC contents, with NE management increased faster than FP. The annual SOC contents rise rates of NE treatment in 0-5 cm, 5-10 cm and 10-20 cm soil profile were 0.28, 0.27, 0.34 g/(kg·a), respectively, which were 7.7%, 68.8% and 126.7% higher than those of FP treatment. The average annual carbon input of NE and FP treatment from straw returning were 8.5, 8.7 t/(ha·a), respectively, and the SOC sequestration rates were 1.35, 0.68 t/(ha·a),respectively, and the SOC sequestration efficiencies were 18.6% and 0.4%, respectively, which shown a significant difference. NE management could improve N use efficiency and increase SOC sequestration. Long-term NE management is one of the important measures for fertilizer saving, efficiency strengthen and SOC pool richen in wheat-maize rotation system. It would play a crucial role in ensuring food security and realizing agriculture green development.

The objective of the test is to reveal the effects of long-term manure and its combination with nitrogen fertilizer on nitrogen mineralization of non-calcareous fluvo-aquic soil,and exploring the relationship between crop yield and mineralization.Based on the long-term fertilization test in Laiyang,Shandong Province,which was started in 1978,the effect of long-term fertilization on nitrogen mineralization was studied by ISC-IERB(In-situ Soil Core and Ion Exchange Resin Bag),and the correlation analysis between the crop yield and the mineralization was carried out.Long-term application of organic manure and nitrogen fertilizer could significantly increase the non-calcareous soil total nitrogen,mineral nitrogen,net nitrogen mineralization,nitrogen uptake and yield of winter wheat or summer maize,and in the same manure(or nitrogen fertilizer) level,the increase of the amount of nitrogen fertilizer(or manure) was increased,among these,the increase of M₂N₂(combined application of high amount of manure and high amount nitrogen fertilizer) was the highest,and the yield of winter wheat and summer maize respectively were 6 803,11 935 kg/ha;long-term fertilization in summer maize season soil nitrogen net mineralization,net nitrogen mineralization rate was significantly greater than the winter wheat season,the increase of fertilization treatment were 7.1%-62.7%,16.2%-76.0%;the correlation analysis showed that the yield of winter wheat and summer maize and pre sowing soil total nitrogen,mineral nitrogen content,net mineralization of nitrogen was significantly relativity,but not significantly relativity with nitrogen leaching amount.Application of organic manure and nitrogen fertilizer is an effective means to increase the potential of soil nitrogen supply,plant and season is an important factor to affect the mineralization of soil nitrogen.

The objective of this study was to investigate the influence of application of biochar and biochar compound fertilizer on soil enzyme activity under test of improving brown soil for the sixth year in a row,and it also revealed the effect of biochar on agricultural soil micro-environment.A micro-plot (2 m²) field experiment was conducted from 2009 to 2014 with peanut as tested crop.Four treatments were designed:corn straw returning in combination with NPK (CS),pig manure in combination with NPK (PMC),biochar from corncob in combination with NPK (BIO),and biochar-based compound fertilizer (BF).Catalase,invertase,urease,MBC and soluble carbon of peanut were determined using their relevant methods before sawing and at different developmental stages in 2014.Before planting and mature period,the catalase activity of BIO was close to CS and PMC,the catalase of BIO was lower than that of CS and PMC.Except mature period,invertase activity of BIO was higher than CS and PMC at all growth stages of peanut.Compared with other growth stages,catalase activity of BF was higher than CS and PMC at seeding stage.Only at podding stage,soil invertase activity of treatment BF was higher than that of treatment CS and PMC.Compared with CS and PMC,BIO and BF on urease activity did not show obvious regularity.The positive effect of using biochar and biochar-based compound fertilizer on microbial activity was lower than pig manure application.Compared with CS and PMC,BIO improved the content of DOC at flowering-stage.Biochar induced catalase activity and content of DOC,but improved invertase activity.Application of biochar-based compound fertilizer induced catalase,invertase activity and content of DOC.Compared with CS and PMC,BIO and BF on urease activity did not show obvious regularity.Using biochar and biochar-based compound fertilizer of improve activity of microbial in the straw returned and the pig manure application.

In order to clarify the effects of micro-sprinkling irrigation and nitrogen fertilizer application rate on grain filling characteristics and nitrogen uptake and utilization of winter wheat,two years field experiment was carried out with the main cultivars of wheat variety Jimai 22 as materials. There were three nitrogen treatments(N1,45 kg/ha;N2,90 kg/ha;N3,135 kg/ha) under the condition of micro-sprinkling 4 times(S4,jointing stage+booting stage+flowering stage+grain filling stage) in this study,the integration of water and fertilizer technology was used,and flooding irrigation(CK,jointing stage+flowering stage,N 90 kg/ha at jointing stage) was designed as control. Grain yield,leaf chlorophyll content,dry matter accumulation in grain filling stage,nitrogen accumulation,distribution,translocation in different stages and nitrate nitrogen content in soil were investigated. The results showed that the grain yield was increased under the conditions of micro-sprinkling,especially in the S4N2 treatment,which increased by 10.5% to 24.5% as compared with CK. The increase in grain yield was mainly attributed to the significant increase in thousands grain weight. In 2013-2014 and 2014-2015,the thousands grain weight of S4N2 was increased by 3.47 g and 5.97 g as compared with CK. Micro-sprinkling significantly(P<0.05) increased grain filling duration,especially postponed the terminal time of grain peak filling period and thus extended the grain filling peak duration;at the same time,the theoretical maximum grain weight,maximum and average grain filling rates of S4N2 were significantly higher than other treatments. The content of chlorophyll in micro-sprinkling treatments were significantly higher than CK,and the leaf functional period was prolonged in micro-sprinkling,which promoted grain filling and dry matter accumulation in grain. Compared with flooding irrigation,micro-sprinkling treatments decreased the translocation of nitrogen pre-anthesis and its contribution to grain nitrogen but increased the contribution of post anthesis nitrogen to grain nitrogen,especially in stem and leaf. The grain nitrogen accumulation,nitrogen partial productivity,and nitrogen uptake index were also higher in micro-sprinkling treatment than in control,and the nitrogen fertilizer is mainly concentrated on 0-80 cm soil layer in winter wheat growing period under micro-sprinkling conditions,which reduced nitrate leaching to the deeper soil. Comprehensively,it was concluded that high yield and high nitrogen use efficiency can be realized under the optimal nitrogen application rate(90 kg/hm²) and multiple micro-sprinkling condition in winter wheat.

In order to explore the effects of cattle manure on soil salinity and sodicity on the sodic soil in long-term experiments,the experiments were performed in a randomized complete block design with four treatments;soils that received manure applications for 8,12,18 years were used as the experimental treatments,and soil that did not receive cattle manure application was used as the control treatment(CK).The results showed that the application of cattle manure to saline-sodic soil resulted in a reduction in the bicarbonate ion(HCO₃^-)contents,the elimination of carbonate ions(CO₃^2-),the decrease in soil bulk density(ρ_b),the increases in soil porosity(f_t)and soil organic matter(SOM),the decreases in the exchangeable and soluble sodium ion (Na⁺)contents associated with increases in the exchangeable calcium ion(Ca²⁺),soluble potassium ion(K⁺),and magnesium ion(Mg²⁺)contents compared to those in untreated soil.The soil exchangeable sodium percentage(ESP)and pH were both significantly and positively correlated with the exchangeable Na⁺ and HCO₃^-,and CO₃^2- contents,and soil pH was significantly and negatively correlated with SOM.Regression analysis showed that the dominant factors affecting the sodium absorption ratio(SAR)were the soluble Mg²⁺ and Na⁺ contents in the soil.Pearson correlation analysis showed that there were significantly negative correlation between the accumulated amount of cattle manure among the indicators of soil salinization degree,such as pH,EC,ESP and SAR.It was concluded that long-term manure application significantly decreased the soil pH,ESP,electrical conductivity(EC)and SAR due to the replacement of soil colloidal Na⁺ with Ca²⁺,the leaching of soil soluble salts from the topsoil and changes in the soil soluble salt ion composition.These outcomes were likely due to the decrease of ρ_b associated with increase of f_t and Ca²⁺ and Mg²⁺ contents caused by annual manure application.

Yield and nitrogen accumulation of maize will decline under soil acidification,but the physiological mechanism is not clear.Field experiment was conducted with four different soil acidity gradients:nautral acid(pH=7,CK),weak acid(pH=6,T1),medium acid(pH=5,T2)and strong acid(pH=4,T3),comparing yield,nitrogen accumulation,grain protein content,nitrogen metabolism-related enzyme activities,gene expression,nitrate nitrogen,ammonium nitrogen,soluble protein,free amino acid content in leaf and stem of maize.The results showed that compared with CK,the yield of T1,T2 and T3 treatments declined by 4.2%,30.7% and 52.3%,respectively.Grain number per spike decreased by 1.8%,28.1% and 42.8%;grain protein content showed a downward trend with T3 treatment significantly reduced by 14.5%.At the big flare stage,with the increase of soil acidity,nitrogen accumulation in leaves showed a downward trend,it was significantly decreased in T2 and T3 treatment by 28.1% and 56.2%,respectively.In stem,the nitrogen accumulation increased firstly and then decreased.Compared with CK,T1 treatment was significantly increased by 33.1%,and T3 treatment significantly decreased by 65.4%.At the big flare stage, the activities of nitrate reductase, glutamate dehydrogenase and glutamate synthase in leaf and stem under T3 treatment were significantly higher than those in CK, while the activities of glutamine synthase in leaf were significantly decreased. The amino acids in stem decreased first and then increased.With the increase of soil acidity,the expressions of ZmGln2 and ZmFd-GOGAT were up-regulated,which promoted the assimilation of {{\mathrm{NH}}_4}^{+} released by photorespiration and {{\mathrm{NH}}_4}^{+} produced by {{\mathrm{NO}}_3}^{-} reduction;the down-regulated expression of ZmGln1.2-ZmGln1.4, ZmNADH-GOGAT2 in leaf and ZmNADH-GOGAT1 in stem decreased the assimilation of {{\mathrm{NH}}_4}^{+} released by catabolism.By up-regulating or down-regulating the expression of relevant genes,maize could promote the production of more free amino acids and soluble proteins during nitrogen metabolism to resist acidification stress,but also reduced the nitrogen accumulation,resulting in lower yield and grain protein content.

In order to study the influence of different application amounts of charcoal on the microbial diversity in tobacco rhizosphere soil, with the rhizosphere soil of flue-cured tobacco variety Yunyan 87 as the research object, we compared the situation by applying different amounts of charcoal, and conducted high-throughput sequencing of rhizosphere soil ITS2 region and 16S rDNA-V4 region with progressive treatment with 3 application amounts of charcoal; through bioinformatics analysis of data, we obtained the OTU abundance, distribution,α diversity, community species composition and abundance information of microorganisms in rhizosphere soil when different treatment methods were used, and conducted PCA clustering analysis and UPGMA clustering analysis of the community composition and abundance. The results showed that within the application scope of 50-150 g/tree, by increasing the application amounts of charcoal, it could increase the variety diversity and distribution uniformity of bacteria in rhizosphere soil, while it would reduce the variety diversity and distribution uniformity of fungus; compared to the control group where no charcoal was applied, after applying the charcoal with the amounts of 50, 100,150 g/tree, the abundances of Proteobacteria bacteria had declined by 4.1%, 2.7% and 0.7% respectively; the abundances of Acidobacteria bacteria increased by 10.4%, 8.1% and 7.7% respectively; the abundances of Actinobacteria bacteria were all lower than the abundance of control group; the difference in abundance of Gemmatimonadetes bacteria between various groups was very small. After applying the charcoal with the amount of 50 g/tree, the abundance of Zygomycota fungus had declined by 12.38% compared to the control group(50.92%), and then, with the increased of the application amount of charcoal, the abundance of Zygomycota fungus gradually increased to 53.68%; on the contrary, after applying the charcoal with the amount of 50 g/tree, the abundance of Ascomycota fungus had increased by 10.15% compared to the control group(30.63%), and then, with the increased of the application amount of charcoal, the abundance of Ascomycota fungus gradually declined to 29.11%; after applying the charcoal with the amount of 50 g/tree, the abundances of Basidiomycota and Chytridiomycota funguses almost had no change, and then, with the increased of the application amount of charcoal, the abundances of Basidiomycota and Chytridiomycota funguses presented the trend of increased first, and then declined; various treatment methods did not have significant influence on the abundance of Glomeromycota fungus. By studying the influencing method and action rules of charcoal application on the micro-ecology of tobacco rhizosphere, it can provide theoretical basis to the application of charcoal in tobacco field.

To increase crop yields,reduce the application of chemical fertilizers,and improve nutrient utilization efficiency,N-efficient maize cultivars were screened and popularized. An understanding of nitrogen uptake,utilization,and field balance in maize cultivars with contrasting nitrogen efficiency response to N management is essential for efficient breeding and cultivation of maize to produce fodder and bio-energy. To determine the effects of N management on these factors during maize cultivation,a two-year field experiment was conducted in 2015 and 2016 in a subtropical semi-humid climate zone. The results showed that the proportion of N in the stem plus sheath and leaves in ZH311 during VT and R6 was significantly higher than that of XY508. In addition,the N accumulation into grain post-silking(NAG)and contribution of NAG to grain(CNAG)of ZH311 were significantly higher than those of XY508,while the N redistribution rate(NRR)and contribution of NRA to grain yield(CNRA)of ZH311 were significantly lower than those of XY508. The higher proportion of N in the vegetative organs of a N-efficient cultivar,ZH311,led to a significantly higher N accumulation in each stage than that observed for the N-inefficient cultivar XY508. The N accumulation advantage of ZH311 was higher after silking than before silking. The high post-silking N accumulation of ZH311 inhibited the pre-silking N transport that determines the N transport rate and contribution rate to grain of pre-silking N accumulation,which were significantly lower than those of XY508. Meanwhile,the N uptake efficiency,N recovery efficiency,and N partial productivity of ZH311 were significantly higher than those of XY508. Compared with that of XY508,the root system of ZH311 could more effectively absorb and utilize inorganic N in the 40-80 cm soil layer,reduce N deposition,and significantly decrease apparent N losses. The differences in apparent N losses between the two cultivars were mainly elicited post-topdressing. In summary,ZH311 has not only a higher yield per unit area than XY508,but also lower N losses,consequently reducing environmental risks.

In order to explore the influence of the typical long term orientation of straw returning to field on soil microbial diversity and the relationship between soil microbial diversity and ecological environment effect, using 16S rDNA PCR sequencing technology,continuous 6 years of long term positioning of straw to field test,analysis of the composition of soil bacterial community structure.The results showed that soil microbial community diversity and species richness could be promoted after long-term fertilization of straw and organic fertilizer.The dominant species of bacteria in the soil after straw returning to field were the deformation of the Proteobacteria and Acidobacteria.Principal component analysis that significant differences in the types and contents of microorganisms among different treatments.WC and WCN treatment of N, P, K and other available nutrient content was significantly different.WCN treatment in the N, P, K and other available nutrients, organic carbon content an d invertase, urease, cellulase activity was significantly higher than WC.The application of nitrogen fertilizer could significantly increase the soil nutrient content and enhance the soil enzyme activity, conducive to the improvement of soil is bacterial community diversity and stability, and improve the ecological environment of soil, so as to promote the increase of crop yield.

The effect of soil amendments on soil microbial communities,quality and yield of tomato in protected house were investigated for providing a scientific basis for reasonable use of soil amendments.A field experiment was initiated in a planting tomato greenhouse with different kinds of soil amendments(lime nitrogen,fosthiazate,abamectin and substrate).Changes of bacteria,fungi,quality,yield were monitored.Results showed that four different types of soil amendments could significantly increased the number of soil bacteria,fungi,actinomycetes and antagonists,while the numbers of bacteria and fungi in the later growing period of tomato compared with the middle growing period were decreased;the contents of lycopene and Vc reached the highest under substrate treatment for 8.75 mg/100g,78.60 mg/kg,respectively;the soluble sugar content ranged from 2.85% FW to 3.29% FW;compared with other treatments,the sugar acid ratio of CK,substrate and abamectin were 7.57,6.91 and 7.70,respectively,taste the best;under substrate treatment,the yield of tomato was the highest for 139 059.30 kg/ha,which was increased by 21.18% compared with CK.Considering the taste quality and yield,substrate could be used as a preliminary reference for tomatoes production.

To study the effects of cotton straw returning soil on soil microbes quantities and enzyme activities,experiments were conducted at the Experimental Station of Shandong Agricultural University with two treatments(4-year straw returning soil and no straw returning soil) to investigate soil microbes quantities and enzyme activities across 0-60 cm depths after cotton straw returning for four consecutive years.The main results indicated that cotton straw returning soil significantly increased the quantity of total microbe by on average 19.87%(0-20 cm),20.07%(20-40 cm) and 56.15%(40-60 cm),including soil bacteria and fungi quantity significantly increased by on average 20.91%,26.38%(0-20 cm),20.59%,31.18%(20-40 cm),56.85%,32.30%(40-60 cm),respectively,comparing to no straw returning soil treatment;soil actinomyces quantity increased by on average 4.29%(P>0.05),11.62%(P<0.05),54.00%(P<0.05)across 0-20 cm,20-40 cm,40-60 cm depths,respectively,comparing to no straw returning soil treatment.Cotton straw returning soil had no significant effect on soil urease activities at 0-20 cm depth,comparing to no straw returning soil treatment,while straw returning soil significantly in creased soil urease activities across all sampling times except September at 20-40 cm and all sampling times except July at 40-60 cm depths by on average 13.43% and 24.03%,respectively.Except May at 20-40 cm and August at 40-60 cm depths,soil sucrase activities after cotton straw returning soil significantly increased across 0-20 cm,20-40 cm and 40-60 cm depths by on average 27.08%,46.96% and 57.59%,comparing to no straw returning soil treatment.Except July and August at 0-20 cm depth,cotton straw returning soil significantly increased soil catalase activity at by on average 8.73%,comparing to no straw returning soil treatment,while straw returning soil had no significant effect on soil catalase activity across 20-40 cm and 40-60 cm depths except May and June at 20-40 cm depths.These results indicated that cotton straw returning soil could maintain and improved the biological characteristics of the soil.

In order to investigate the effect of fertilizer reduction combined with organic fertilizer on the yield and quality of silage corn and soil nutrient,in 2019 and 2020,the effects of fertilizer reduction and organic fertilizer on agronomic traits,yield, quality,soil nutrient content and fertilizer utilization rate of silage corn were studied.As a result,the yield of silage corn was significantly affected by different fertilization treatments,and the yield of mixed application of organic fertilizer and slow control fertilizer reached 55 084.75 kg/ha,dry matter production reached 24 192.11 kg/ha.There was no significant difference in yield between slow controlled fertilizer constant and slow controlled fertilizer reduction of 20%,that was,excessive fertilization had no significant effect on yield.The accumulation of N,P and K under T2 treatment was 234.83,173.75,35.72 kg/ha,and significantly higher than other treatments.The maximum nitrogen fertilizer productivity of silage corn under T4 treatment was 166.46 kg/kg,and the maximum nitrogen fertilizer utilization efficiency under T1 treatment was 0.80 kg/kg,which indicated that the mixed application of organic fertilizer and inorganic fertilizer could improve the productivity of silage corn.After T4 treatment,the crude fat content of silage corn was the highest,and the application of organic fertilizer could increase the crude fat content of silage corn,and also increase the content of acid washing fiber.The yield of silage maize was correlated with urease,catalase and available phosphorus content,the correlation coefficients were 0.845,0.798,0.784.The results showed that fertilizer reduction and organic fertilizer application in Southwest China could significantly improve the yield and quality of silage corn,which was beneficial to the protection of farmland ecological environment and the sustainable utilization of soil fertility.

In order to study the effects of different amount of biochar application combined with nitrogen fertilizer on the growth of flue-cured tobacco and the main chemical composition of tobacco leaves.Yunyan 87 was selected as testing material and a field experiment was designed to study the effects of nine different amount of biochar application combined with nitrogen fertilizer on the growth of flue-cured tobacco and the main chemical composition of tobacco leaves.The results showed that biochar application combined with nitrogen fertilizer could regulate and promote the growth of flue-cured tobacco,accelerate the speed of the leaves,but amount of biochar application was not positively correlated with the role of promotion tobacco growth,when applied to the biochar more than 3 750 kg/ha,and nitrogen fertilizer at 112.5 kg/ha,the role in promoting tobacco growth gradually decreased.Biochar application combined with nitrogen fertilizer could promote root growth,and improve the amount of dry matter accumulation of flue-cured tobacco.Coordinate the content of total sugar and reducing sugar,decline the content of starch,and improve the content of potassium in tobacco leaves and improve the combustibility of tobacco leaves.At the same time,it could also improve the ratio between sugar and nicotine,the ratio between sugar and nitrogen and the ratio between sugar and nitrogen of tobacco leaves.It was harmful to improve the ratio between sugar and nitrogen and the ratio between potassium and chlorine of tobacco leaves that a lower proportion of biochar application combined with nitrogen fertilizer that was 3 000 kg/ha biochar and 75.0 kg/ha nitrogen fertilizer.It was concluded that 3 750 kg/ha biochar and 112.5 kg/ha nitrogen fertilizer was the optimal proportion which had faster growth of tobacco plant and the appropriate content of main chemical composition of tobacco leaves.

To investigate the reasonable amounts of NPK fertilization on peanut in the rotation of peanut and rye during one year,the effects of the different applying amounts of NPK fertilizers on the yield and quality of peanut,the SPAD value and the gas exchange parameters of the leaf of peanut in pod setting stage,and the soil nutrients in the harvest stage of peanut,and the grass yield and the nutrients accumulation above ground of rye were studied by the combining methods of the field investigation and the laboratory analysis.The results showed that the pod yield,the hundred pods weight and the hundred grains weight of peanut,and the grass yield and the protein yield of the following rye were all improved with the increase of NPK fertilizers amounts.However,the excessive fertilization of NPK would cause the increment of the pod yield of peanut being not significant.And the protein content,the fat content,the O/L value of the peanut grain increased significantly when the NPK fertilizers amounts were added to a certain level.And improving the NPK fertilizer levels not only could enhanced significantly the chlorophyll content,photosynthetic efficiency of peanut pod leaf,but also could significantly improve the Alkaline P,Alkaline K content in soil except for the SOM content,alkaline hydrolysis nitrogen content.The C,N,P and K nutrients of rye accumulated with the increase of the fertilization level,and the maximum amounts of the accumulated nutrient was C,and the mini was P.And the reasonable applying amounts of NPK were N 56.25 kg/ha,P₂O₅ 243.75 kg/ha,K₂O 187.50 kg/ha respectively.In conclusion,the rational application of NPK fertilizers can increase the yield,quality and photosynthetic efficiency and nutrients content in soil.

In view of a series of problems of a large number of inputs bringing the low utilization rate of water and fertilizer and nutrient loss in current production of high yield of potato,the effect of different fertilizer treatments on the yield,quality and the fertilizer utilization ratio of potato under mulching drip irrigation were studied in this paper under open field conditions.The different fertilizer treatments were composed of CK(No fertilizer),D1(1 245 kg/ha of slow-released of fertilizer),D2(1 500 kg/ha of compound fertilizer) and D3(675 kg/ha of water soluble fertilizer),and with farmers' conventional irrigation fertilization treatment CF(1 500 kg/ha of compound fertilizer with furrow irrigation) for comparison.The results indicated that different fertilization treatments under drip irrigation conditions increased the plant height,root length,root volume,leaf area index,chlorophyll content and plant fresh weight of potato and reduced the MDA content and SOD activity of potato.The test results also indicated that compared with conventional furrow irrigation fertilization,the treatments of D1,D2 and D3 with drip irrigation under mulch film promoted the potato on the absorption and accumulation of soil nutrients,increased the potato production by 18.4%,13.3% and 26.0% respectively.Starch content increased by 10.3%,5.5%,15.1% respectively,and the crude protein content increased by 12.9%,8.6% and 13.8% respectively.While the soluble sugar content reduced by 5.6%,2.4% and 15.3%respectively.Especially the D3 treatment with drip fertigation increased the fertilizer utilization ratio of nitrogen,phosphorus and potassium by 22.7%,20.5% and 23.5% respectively.From the point of view of the efficiency of agricultural use and the partial productivity of fertilizer,phosphate fertilizer was higher than that of nitrogen fertilizer and potassium fertilizer.Therefore,we should pay attention to the promotion of fertigation technology and the scientific application of fertilizer in potato production.

To assess the peanut rhizosphere bacteria community structure in response to salt stress at different development stages, the peanut variety Huayu 25 was used as experimental material, and a pot experiment was set with three salt concentrations to study the effect of salt stress on peanut yield and analyze the changes of microbial community structure of peanut rhizosphere at flowering and harvest stage under salt stress by high-throughput sequencing technology. The results showed that the rhizosphere microbial composition of peanut were basically similar under different salt stress treatments, but the diversity and richness significantly varied between flowering and harvest stage. Under higher salt stress, the diversity and richness of rhizosphere bacterial community were increased at the flowering and needling stage but decreased at the harvest stage. The dominant bacteria phyla of all soil groups were Proteobacteria, Actinobacteria, Chloroflexi, Acidobacteria, Verrucomicrobia, Bacteroidetes, and Patescibacteria. The relative abundance of Cyanobacteria, Gammaproteobacteria, Verrucomicrobiae and Bacteroides significantly increased under salt stress, especially at the flowering and needling stage. Hierarchical clustering revealed that the microbial community diversity was markedly altered by the salt concentrations and growth stages, samples of the same growth period were clustered into one group under salt stress. KEGG functional prediction analysis indicated that sequences related to carbohydrate metabolism, amino acid metabolism, energy metabolism, and metabolism of cofactors and vitamins were enriched, whereas that of signal transduction mechanisms, lipid metabolism, replication and repair, xenobiotics biodegradation and metabolism, metabolism of other amino acids, and folding, sorting and degradation were decreased. Among them, salt stress increased the abundance of functional groups involved in substance and energy metabolism, membrane transport, translation, replication and repair, and signal transduction, but decreased the 100 fruit weight and 100 kernel weight of peanut resulted in the decrease of peanut yield. Therefore, salt stress had a great impact on the peanut rhizosphere bacterial community structure and peanut yield. The salt tolerance of peanut could be enhanced by improving soil microbial environment. The results provided a theoretical basis for the development of peanut production in saline-alkali areas.

In order to investigate the relationship of nitrogen fertilizer(N) and planting density(D) with the yield, quality and starch pasting properties of fresh edible sweetpotato, the field experiments were carried out in 2017 and 2018 using Xushu 32 and Xuzishu 5 as the research subjects, and setting three nitrogen fertilizer levels and five planting densities. The results showed that:The storage root yield of the two varieties decreased with the increase of nitrogen application, while first decreased and then increased with the increase of density. In general, the maximum storage root yield came from the treatment of N0(0 kg/ha) nitrogen level and D1(43 785 plant/ha) density level; Nitrogen application reduced the dry matter rate and significantly increased the protein content in the two sweetpotato varieties. With the increase of planting density, the dry matter rate, starch content and protein content of the two cultivars generally increased first and then decreased. The reduced sugar showed a downward trend, while the soluble sugar content fluctuated, which was the lowest at D3 level; On the whole, the peak viscosity, hot paste viscosity and breakdown value of starch in the two varieties were significantly reduced and the setback value was significantly increased, resulting in the decline of cooking and eating quality. The peak viscosity, hot paste viscosity, breakdown value and cool paste viscosity fluctuated with the increase of density; the maximum values were from the D3 level for Xushu 32, and from the D2 level for Xuzishu 5. The effects of nitrogen application and planting density on RVA spectrum of sweetpotato starch were different among varieties and characteristics. Based on the results of this experiment, applying a large amount of nitrogen to a plot with high soil fertility reduced the storage root yield of sweetpotato, and negatively affected the nutritional quality and edible quality. At the density level of 43 785 plants/ha, the storage root yield was the highest. However, proper increase of density was beneficial to the improvement of nutritional quality, cooking quality and eating quality.

This study investigated the accumulation and distribution of dry matter,nitrogen(N)and zinc(Zn)of summer maize under N and Zn fertilization,to provide a basis for reasonable application of zinc fertilizer and combined fertilization.Split-split design was used with three N rates(90,180,225 kg/ha N)as the main factor,two Zn rates(0,4.5 kg/ha ZnSO₄·7H₂O)as the second factor,two varieties(ZD958 and GSY66)as the third factor.The effect of N and Zn application on the grain yield,dry matter accumulation dynamic and N and Zn absorption,accumulation and distribution of each organ of different maize varieties by field experiment.The results showed that the grain yield achieved 9.77,10.42 t/ha under the N rates of 180,225 kg/ha,respectively,increased by 18.0% compared with 90 kg/ha.The treatment of 225 kg/ha N had the highest plant dry matter accumulation after silking,while the treatment of 90 kg/ha had higher ratio of cob and grain dry matter at the mature stage.Highest N concentration in each organ,Zn concentration in the stem and N and Zn accumulation in the leaf and grain were obtained in the treatment of 225 kg/ha,while highest Zn concentration in the sheath,bract and grain and ratio of grain N and Zn were found in the treatment of 90 kg/ha.No effect was found in the grain yield and dry matter accumulation and distribution under two Zn treatments.Zn application significantly increased N and Zn concentration and accumulation but decreased distribution ratio of grain N and Zn by 6.93,6.86 percentage points,respectively.Relative to GSY66,ZD958 had higher grain yield and dry matter ratio,and increased dry matter by 29.2% at maturity.Besides this,ZD958 decreased grain N and Zn concentration by 8.9% and 5.3%,respectively,but improved grain accumulation and distribution ratio.Correlation analysis showed that grain yield and N concentration in the stem,leaf and grain were significantly positively correlated.There was also a significantly or extremely significantly positive correlation between Zn concentration in the leaf and N concentration in the sheath and grain,between Zn concentration in the cob and N concentration in the sheath,cob and bract.These results suggested that combination of N and Zn fertilizers could increase yield and plant dry matter accumulation,enhance the N and Zn absorption and accumulation in each organ especially grain,but decrease distribution ratio of N and Zn in the grain.

Based on a long-term field experiment,the effects of different tillage measures on the carbon storage of soil and the utilization efficiency of water and nitrogen in wheat were studied.Four models were designed:deep tillage(T1),deep tillage plus straw returning(T2),shallow tillage(T3),and shallow tillage plus straw returning(T4).The results showed that straw returning had a certain infuenceron soil carbon accumulation.Compared with the organic carbon storage before sowing,it was higher at winter stage in 0-20 cm soil,reached to the highest at jointing stage in 20-40 cm,and also had the maximum value at jointing stage in 40-60 cm except T1 treatment.During the whole growth period,the organic carbon storage was generally higher in straw returning treatment than in no straw returning.T1 treatment increased the soil water content in early growth stage of wheat.The crop water consumption of T2 treatment was 4.2% higher than that of T4 treatment.Straw returning could increase the water use efficiency of wheat.The water use efficiency and irrigation water use efficiency of T2 were 24.9% and 27.6% higher,respectively,than that of T4.Except in flowering stage,the nitrogen content of plant was higher in deep tillage than in shallow tillage.And T2 treatment could significantly improve the nitrogen accumulation of wheat,44% higher than that of no straw returning.Deep tillage increased the nitrogen utilization efficiency by 57.2% compared with the shallow tillage straw returning treatment inhibited the growth of wheat in early growing stage,but promoted the dry matter accumulation in later growing stage.Straw returning could increase the grain number of wheat,so as to raise the grain yield.The grain yield of T2 was 22.1% higher that of T3,and 6.7% higher than that of T1,while it was 14.4% higher in T1 than in T3.The results suggested that straw returning and deep tillage could increase the carbon storage of soil,improve the use efficiency of water and nitrogen,and then increase the grain yield of wheat.

Based on randomized block experimental design,a field experiments was conducted to investigate the effects of different nitrogen fertilizer,high efficiency organic fertilizer and amendments on wheat yield,maize yield and soil fertility in the rotation system of wheat and maize on coastal saline areas.The aim of these experiments was to providing a certain theoretical guidance about soil fertility and crop yield in coastal saline soil.The results showed that the application of nitrogen fertilizer,high efficiency organic fertilizer and amendments could increase grain yield of wheat.And the yield increased 9.52%-29.52%,2.30%-17.82%,2.19%-11.48% respectively.The application of nitrogen fertilizer,high efficiency organic fertilizer could increase grain yield of maize,and the yield increased 29.37%-45.74%,1.69%-11.15% respectively.There was obvious yield increasing effect on corn yield after wheat amendments,and the yield increased 3.50%-8.33%.Application of nitrogen fertilizer,high efficiency organic fertilizer and amendments had a significant effect on improving soil fertility in coastal saline soil.O3(N₂O₃A₂) had the highest available nitrogen,available phosphor,available potassium content in all treatments;Application of amendments increased soil organic matter content and decreased the soluble salt contents in soil.Under the conditions of this experiment,the highest wheat and maize annual production reached 16 770.46 kg/ha,which obtained by mathematic simulation,and the optimum economic amounts of nitrogen fertilizer,organic fertilizer and amendment were 763,2 250,3 167 kg/ha,respectively.Therefore,in order to obtain high yield and get higher economic efficiency,we should pay attention to combine application among nitrogen fertilizer,high efficiency organic fertilizer and amendments in the rotation system of wheat and maize on coastal saline areas.

Through 6 years of field experiments,the intention of the experiment was to study the effects of the different fertilizer treatments on the soil humus content changes under the condition of wheat-corn straw returned.The results suggested that humic acid (HA),fulvic acid (FA) and humin (HM) content increased gradually with the increase of age of straw length.Contrast with CK,3 types of straw return to soil humic acid with an average increased of 3.84% to 62.16%,there were significant differences among them.The soil humus (HA,FA,HM) content in WCN treatment was the highest,and the averagely increased 98.16% than CK.WN,WCN and M treatment could improve the content of soil water soluble substance (WSS),the contents of WSS under WC treatment were stable in (0.29±0.11) g/kg level.WCN compared to CK increased by 89.29%.With the increase of straw returning years, the treatment of WCN HA/FA and the PQ value reached maximum in 2014,1.08 and 0.52 respectively.It stated that two seasons could enhance the content of soil humic acid(HA),humin (HM),fulvic acid (FA) and could also significantly improve humus soil humification degree,increase the content of humic acid and make steady growth.

To clarify the suitable application rate of the soluble ammonium polyphosphate fertilizer for tomato,the phosphorous rates of soluble ammonium polyphosphate fertilizer on yield,quality,phosphorous uptake of autumn-winter tomato were studied in a plastic greenhouse.The results showed that the yield of tomato and the fruit weight were highest at the 29 kg/ha,however,when continue to increase the amount of phosphorus,the yield and fruit weight will be lower.The most appropriate phosphorus rate for tomato quality was 29 kg/ha.As the phosphorus uptake of tomato roots,the difference between treatments was not significant; After fitting,the most appropriate phosphorus rate for tomato fruit and whole-plant were 21.17 kg/ha and 25.79 kg/ha respectively.The phosphorous utilization efficiency (PUE) was higher than other treatments at 29 kg/ha.In summary,the most appropriate phosphorous rate for a higher autumn-winter tomato yield was 29 kg/ha under this soil fertility.

In order to promote the further promotion of green manure planting in Tianjin, a field experiment was adopted, and 9 spring Brassica napus L. varieties were overturned with spring fallow fields as a control to study the effects of different spring Brassica napus L. on soil potassium content and maize nitrogen metabolism.The results showed that there were differences in the biomass and nutrient content of different spring Brassica napus L. varieties. Among them, Zhongyoufei 1901(7 716.50 kg/ha), 1804(6 577.02 kg/ha), and 1907(6 457.03 kg/ha) had higher biomass and nutrient content.The change trend of soil total potassium and available potassium in 2019 was the same as 2020. Among them, the content of total potassium and available potassium in the soil under the treatment of spring Brassica napus L. of Zhongyoufei 1901, 1804, and 1907 was higher than that of other tested varieties in different periods, and the total potassium and available potassium content of soil in 2020 were higher than those in 2019.The potassium uptake by the whole plant of maize and the total potassium uptake by the hectare of the three varieties of maize were higher than those of other tested varieties. Compared with 2019, the potassium uptake of the whole plant of maize treated with different spring Brassica napus L. in 2020 increased by 15.70%-24.34%;the NR and GS activities of the ear leaves in different spring Brassica napus L. treatments increased by 2.16-14.22 nmol/(min · g), 0.99-2.30 μmol/(h · g), respectively. The top 3 NR and GS activities of the maize ear leaves were the same as the potassium uptake of the whole maize plant. Compared with spring fallow, spring Brassica napus L. treatments' yield of maize increased by 10.02%-33.47%, which was 1.09-1.41 times of the spring fallow, and the highest yield in two years was 15 700.94 kg/ha (2020 Zhongyoufei 1901). It could be seen from the path analysis that the nitrate reductase activity of the leaf at the ear position had a direct effect on the protein content of corn grains.In the indirect effect, leaf protein content contributed the most to maize grain protein through leaf nitrate reductase activity.Correlation analysis showed that there were significant and extremely significant positive correlations among Brassica napus L. total potassium, soil potassium, maize potassium uptake, key enzymes in maize leaf nitrogen metabolism, maize leaf protein content, and maize grain protein content.