Effects Of Maize Straw-Derived Biochar On Microbial Amount And Function In Calcareous Arable Soil

Nitrogen fertilizer is one of the most important conditions for improving crop yield and ensuring food security.In order to achieve higher grain yield,nitrogen fertilizer is widely used in agricultural production,but it also brings many negative effects.Therefore,it is one of the urgent problems to be solved to find a way to minimize soil nitrogen loss and increase nitrogen fertilizer utilization.Biochar is a kind of refractory,stable,highly aromatic and carbon-rich solid matter produced by high temperature pyrolysis of biological residues under the condition of hypoxia,and it is a new technology for carbon fixation in arable that has been implemented in recent years.However,conclusions about the effects of biochar application on microbial amount and function in arable soil are different due to factors such as biochar materials and soil types.Therefore,this research prepared biochar from maize straw with a wide range of sources,and studied the effects of maize straw-derived biochar on microbial amount and function in calcareous arable soil of Loess Plateau.This research provides theoretical reference for the application of maize straw-derived biochar in agricultural engineering in the Loess Plateau.The research on bacteria,actinomycete and fungi amount amended with maize straw-derived biochar was carried out in calcareous arable soil of Loess Plateau.Under the condition of applying nitrogen fertilizer,the maize strawderived biochar was mixed with the soil at a proportion of 0%,0.5%,1% and 2%(mass ratio).At the same time,the treatment of no nitrogen fertilizer and no biochar was set as a control.The amount of bacteria,actinomycete and fungi of soil samples were determined at regular intervals,combined with changes of electrical conductivity(EC),readily oxidizable organic carbon(ROC),soil total organic carbon(TOC),organic matter(OM),total nitrogen(TN),ROC/TN,TOC/TN in soil to investigate the effect of maize straw-derived biochar on bacteria,actinomycete and fungi amount in calcareous arable soil,and to analyze the related mechanism.The results showed that the microbial amount of soil showed the following trend: Bacterial>Actinomycete>fungi;The amount of bacteria and actinomycete increased with the incubation process,while the amount of fungi showed a decreasing trend;The addition of maize straw-derived biochar increased the amount of bacteria,actinomycete and fungi in the soil,and the degree of increase improved with the increase of biochar addition ratio;Compared with CK,single application of nitrogen fertilizer inhibited fungal growth during partial incubation period;Correlation analysis showed that there was a significant correlation between soil EC,ROC,TOC,OM,TN,TOC/TN and bacteria,actinomycete and fungi amount,and there was a significant correlation between ROC/TN and bacterial amount.In addition,in order to study the effect of maize straw-derived biochar on nitrogen-transforming bacteria amount and nitrogen-transformation rate in calcareous arable soil of Loess Plateau,this research conducted a 50-day static soil incubation experiment.Under the condition of applying nitrogen fertilizer,the maize straw-derived biochar was mixed with the soil at a proportion of 0%,0.5%,1% and 2%(mass ratio),at the same time,the treatment of no nitrogen fertilizer and no biochar was set as a control.Azotobacter,ammonifying bacteria,ammonia-oxidizing bacteria,nitrite-oxidizing bacteria amount and ammonification rate,ammonia oxidation rate,nitrite oxidation rate of soil samples were determined at regular intervals.At the same time,the regression relationship between nitrogen-transforming bacteria amount and nitrogen-transformation rate was analyzed by linear regression analysis,and correlation relationship between nitrogen-transforming bacteria amount,nitrogen-transformation rate and EC,ROC,TOC,OM,TN,ROC/TN,TOC/TN at the end of incubation in soil was analyzed by correlation analysis,to investigate the effect of maize straw-derived biochar on nitrogen-transforming bacteria amount and nitrogen-transformation rate in calcareous arable soil,and to analyze the related mechanism.The results showed that the addition of maize straw-derived biochar increased azotobacter,ammonifying bacteria,ammonia-oxidizing bacteria,nitrite-oxidizing bacteria amount and ammonification rate,ammonia oxidation rate,nitrite oxidation rate in calcareous arable soil,and the degree of increase improved with the increase of biochar addition ratio;Regression analysis showed that there was a significant regression relationship between nitrogen-transforming bacteria amount and nitrogen-transformation rate in the process of nitrogen-transforming in calcareous arable soil,and the macroscopic nitrogen-transformation rate was a direct reflection of the micro-scale nitrogen-transforming bacteria amount;Correlation analysis showed that there was a significant correlation between soil EC,ROC,TOC,OM,TN,TOC/TN and nitrogen-transformation.