Effect Of Straw Biochar On Nitrogen Fixation And Its Availability In Paddy Soil

Nitrogen plays an important role in the growth of rice and the formation of yield.However,in agricultural production,large amounts of nitrogen fertilizers are used,leading to increased production costs,increased nitrogen loss,lower nitrogen use efficiency,and decreased soil quality.During the double-season rice production process,a large amount of straw is produced.Using straw to prepare biomass carbon to return to the field can reduce the pollution and waste of straw,and it has strong adsorption and holding effect on nitrogen,but biomass carbon to double-cropping rice soil nitrogen The mechanism of the effect of adsorption and retention of the element on adsorption is not yet clear.In order to reduce the loss of nitrogen in paddy soils and increase the efficiency of nitrogen absorption and utilization of crops,we provided solutions to this study.In this study,adsorption experiments,soil column leaching simulation experiments,and field positioning experiments were conducted to investigate the effect of postgraduate material carbon on the absorption and utilization of nitrogen in rice plants and yield.Effects,microbiological mechanisms and mechanisms of adsorption,retention and transformation of soil NH₄⁺-N and NO₃^--N.The main findings are as follows:（1）Adsorption experiments showed that with the increase of the concentrations of NH₄⁺-N and NO₃^--N,the adsorption capacity and the adsorption capacity of biochar showed an increasing trend,and the linear Freundlich model could simulate the biomass better.Adsorption of NH₄⁺-N and NO₃^--N from solution by carbon,NH₄⁺-N linear Freundlich model formula:ln Q_e=1.0905ln C_e-2.6882（R²=0.95）,NO₃^--N linear Freundlich model formula:ln Q_e=1.4086ln C_e-0.3696（R²=0.99）.（2）Soil column leaching simulation experiments show that biomass carbon can promote soil adsorption and retention of NH₄⁺-N,reduce soil leaching of NH₄⁺-N,and slow down the decline of NH₄⁺-N concentration in the leach solution.Compared with the treatment without added biomass carbon,the soil NH₄⁺-N leaching loss in soil layers after treatment with 2%,4%,and 6%biomass carbon decreased,reaching a maximum of153.23%.2%treatment reduced NO₃^--N leaching in soil,up to 7.72%.With the addition of4%and 6%ratio of biomass carbon,the NO₃^--N leaching loss in soil column soils increased by up to 36.57%.（3）The field positioning test showed that the soil organic matter,available potassium,and p H value increased as the amount of biomass carbon applied increased,the p H value of rice soil increased by 1.47%to 6.79%,and the soil available potassium increased by7.11%～64.32%,soil organic matter content increased by 9.54%to 30.28%.In the early growth period（early rice and young panicle differentiation period,heading date and late panicle differentiation period）,the application of biomass charcoal results in a decrease in soil NH₄⁺-N（0-20 cm）content,which is reduced by 4.55%to 14.85%.In the later growth period（early rice maturity,late rice heading and maturity）,the application of biomass charcoal treatment increased soil NH₄⁺-N content by 5.30%to 16.19%.The soil microbial biomass carbon（MBC）and microbial biomass nitrogen（MBN）are directly proportional to the amount of biomass carbon,with an increase of 5.38%to 89.61%.At late rice maturity,the gene abundance of ammonia-oxidizing archaea treated with 40 t hm^-2 biochar alone was significantly higher than that of other treatments,and the abundance of ammonia-oxidizing bacteria treated with 40 t hm^-2 biochar and nitrogen fertilizer was significant.Lower than other treatments.There was no significant difference in soil nar G and nir K gene abundance between early and late rice growth treatments at the same growth stage,but different growth stages had significant effects on the nar G and nir K gene abundances.At the heading stage of early rice,40 t hm^-2 biomass charcoal treatment,20 t hm^-2 biomass charcoal and single application of nitrogen fertilizer at the heading stage of late rice,and 40 t hm^-2 biomass carbon and 40 t hm^-2 biomass at mature stage The nos Z gene abundance of t hm^-2 treatment with biomass charcoal and nitrogen fertilizer was significantly higher than other treatments during the same period.There was no significant difference in nif H gene abundance between treatments during the same growth period.The difference in abundance of nif H genes between early rice and late rice was significant.（4）The field positioning test showed that the number of effective panicles of the biochar-added rice decreased by 0.76%to 7.50%,the number of grains per panicle increased by 3.43%to 18.60%,and the yield increased with the increase of the amount of carbon applied.The increase was 2.6%～10.38%.Under no nitrogen application,the SPAD value,aboveground dry matter,nitrogen concentration,and nitrogen accumulation in leaves of early rice and late rice increased by 0.29%-6.90%and 1.83%-14.87%,respectively,with the increase in the amount of carbon applied.,1.27%to 9.43%and5.69%to 25.48%.Under the condition of nitrogen application,the SPAD values of the leaves of early rice and late rice,the dry matter,nitrogen concentration and nitrogen accumulation of shoots in the early growth stage（early ear and young panicle differentiation stage and heading stage,late rice and panicle differentiation stage）depend on the amount of carbon applied.Increased and decreased,and the reduction ranged from0.48%to 3.48%,from 3.41%to 13.7%,from 0.54%to 10.69%,and from 7.38%to 15.98%,but at the later stage of maturation（early rice maturation,late rice heading and maturity）.The increase in carbon content increased by 0.69%to 17.22%,1.89%to 7.48%,2.79%to17.31%,and 5.02%to 24.83%.