Abstract:

To investigate the effects of different maize straw carbon addition on soil organic carbon and fertilizer improvement,it focused on an in-situ soil column incubation experiment was established on tobacco fields.Four treatments were set,including none straw addition(CK),conventional straw(RS),decomposed straw(DS)and straw biochar(BC).The organic carbon components and structure,soil physical and chemical properties,and enzyme activities of the 0-20 cm soil layer of tobacco field treaded by the four treatments were characterized and analyzed.One-year incubation results showed that:Compared with none straw addition,the three forms of straw carbon addition all significantly increased the content of total organic carbon(TOC)and microbial biomass carbon(MBC)in the soil.Compared with none straw addition,treatments of conventional straw and decomposed straw significantly increased soil dissolved organic carbon(DOC)content,while straw biochar treatment significantly increased particulate organic carbon(POC)content(42.40%).The three forms of straw carbon addition all significantly increased the microbial biomass carbon/total organic carbon ratio and promoted the turnover of soil organic carbon.The functional group structure of SOC was analyzed by ¹³C nuclear magnetic resonance.The results indicated that conventional straw and decomposed straw treatment increased the relative content of Alkoxy carbon(O-Alkyl-C)and Carbonyl carbon(Carbonyl-C)(labile carbon component),while straw biochar treatment increased Alkyl carbon(Alkyl-C)(recalcitrant carbon component),Alkyl carbon/Alkoxy carbon(A/OA)and Hydrophobic-C/Hydrophilic-C(Hydrophobic-C/Hydrophilic-C).Different forms of straw carbon had significantly different effects on soil nutrients and enzyme activities,straw biochar treatment significantly increased by 65.72%,19.93% and 5.77% for the content of available potassium(AK),ammonium nitrogen(AN)and nitrate nitrogen(NN),respectively.Conventional straw and straw biochar treatments significantly increased the activities of sucrase(Su)and urease(Ur).The three forms of straw carbon all had a significant effect on the activity of phosphatase(Ps).Redundancy analysis showed that C/N ratio(C/N),cellulase(Ce)and total nitrogen(TN)were the main factors affecting the organic carbon content,while cellulase,pH,and available potassium were the main factors affecting the organic carbon structure.Overall,the application of maize straw biochar had significant advantages in improving organic carbon content and stability,nutrient content,and enzyme activity in a short term.In the comprehensive soil fertility evaluation,straw biochar had the highest score with 0.57.Maize straw biochar was an effective measure to improve the organic carbon level and soil fertility in the tobacco planting soil.

Key words: Straw carbon form, Organic carbon, Soil fertility, Tobacco planting soil