| In recent years,the decline of soil fertility,the degradation of cultivated land quality and the shortage of water resources have seriously threatened my country’s food security.In the maize production system,the decline of arable land quality caused insufficient utilization of rainfall and exogenous fertilizers,which affected the water and fertilizer utilization of maize.In order to ensure the sustainable development of farmland environment and the yield safety of the maize production system,using biochar to achieve dual carbon and optimize the use of water and fertilizer and resources.The aim of the experiment is to improve soil water,fertilizer and maize yield,biochar as the research object,through randomized block trials,under the rate of 6 t·hm-2 and 12 t·hm-2 carbon application,to study the effects of biochar on maize yield,water use efficiency,soil moisture content,water storage,nitrate nitrogen,alkaline hydrolyzed nitrogen,total nitrogen,phosphorus,available potassium,density and p H.The main findings are as follows:（1）Biochar aging has significant effect on maize yield.The effect of biochar on maize yield is mainly reflected in the number of panicles per plant.The number of panicles per plant in the 1st,2nd and 5th years of natural aging was higher than that of the non-charcoal treatment increased significantly,and the effect on the number of rows and grains per panicle was small.Under the same carbon application period,the maize yield of 12 t·hm-2 carbon application rate was more than 6 t·hm-2;under the same carbon application rate,the maize yield of the 1st and2nd year of aging was more than that of the 5th year and 6th year.Compared with the treatment without carbon application,the yield increase rate of 12 t·hm-2 carbon application rate in the1st year of aging was the largest,reaching 28.3%,and the yield increase rate of biochar with 6t·hm-2 carbon application rate in the 5th year of aging was the lowest,up to 6.9%,while the 6t·hm-2carbon application rate in the 6th year of aging had no effect on maize yield,indicating that the 6 t·hm-2 carbon application rate of biochar in the 6th year of biochar aging had an effect on maize yield.The positive effect of yield disappears,and charcoal needs to be replenished in time.（2）Biochar aging has a significant effect on soil moisture and water storage.Except for the treatments of 6 t·hm-2 in the 5th year of aging,6 t·hm-2 and 12 t·hm-2 in the 6th year of aging,the other biochar treatments all significantly improved the maize of water use efficiency compared with no charcoal treatment（P<0.05）,the improvement ranges from 5.4%to 16.7%（2020）and 2.0%to 27.9%（2021）.The effect of biochar application on soil moisture content and soil water storage was mainly concentrated in the 0-30 cm soil layer,and the 12 t·hm-2biochar in the 1st and 2nd years of natural aging in the field has the highest soil moisture content and water storage in the 0-30 cm soil.Under the same carbon application years,the soil moisture content and water storage capacity of the 12 t·hm-2 carbon application rate were significantly higher than those of the 6 t·hm-2 carbon application rate.Under the same amount of carbon application,the soil moisture content and storage capacity of biochar treated in the5th and 6th years of aging were significantly lower than those in the 1st and 2nd years of aging.There was no significant difference in soil moisture content and water storage between the 6t·hm-2 treatments in the 5th and 6th years of aging compared with the no charcoal treatments.（3）Biochar aging has a certain effect on soil fertility.Except for the 6 t·hm-2 treatment in the 6th year of aging,other biochar treatments can significantly increase soil nitrate nitrogen content.According to the grey correlation analysis results,the soil nitrate nitrogen content in the grain filling stage has a high correlation degree with the yield;In the 1st,2nd,5th and 6th years of aging,the content of soil available potassium in the biochar treatment was significantly higher than that in the non-charcoal treatment.The 12 t·hm-2biochar treatment in the first and second years of natural aging in the field had the most significant increase in soil available potassium,which increased by 78.8%and 70.5%compared with no charcoal treatment,respectively;The soil available phosphorus content of 12 t·hm-2 and 6 t·hm-2 biochar in the 1st and 2nd years of natural aging in the field was significantly higher than that of no charcoal treatment in all growth stages,The soil available phosphorus content of 12 t·hm-2 carbon application rate was higher than that of 6 t·hm-2 carbon application rate.The soil available phosphorus content of the 12 t·hm-2treatment in the 1st and 2nd years of aging was significantly higher than that in the 5th and 6th years of aging,reaching 10.5%and 32.2%,respectively.Comprehensive analysis of the available phosphorus content in the whole growth period showed that there was no significant difference in the soil available phosphorus content with the 6 t·hm-2 carbon application rate in the 5th and 6th years of field aging compared with no carbon application treatment.Redundancy analysis between maize growth and development indicators and soil nutrients in 2020 and 2021 showed that soil alkaline nitrogen,available phosphorus and available potassium accounted for 79.9%（2020）and 77.9%of the changes in the two-year experiment,they are the main fertility index that affects the growth and development of maize.（4）A correlation index for evaluating the fertility improvement of biochar was constructed.The soil alkaline hydrolyzable nitrogen,total nitrogen,available phosphorus,available potassium,bulk density and p H were calculated by the Nemerow index method to calculate the comprehensive soil fertility.Under the same carbon application year,the comprehensive soil fertility of 12 t·hm-2 carbon application rate was better than 6 t·hm-2,and under the same carbon application rate,the comprehensive soil fertility of the 1st and 2nd years of aging was better than that of the 5th and 6th years.By constructing a linear regression prediction model for the evolution of soil comprehensive fertility,it can be seen that,the effective life of 6 t·hm-2carbon application on soil fertility index is about 6-7 years after the application of carbon into the soil,the effective years of 12 t·hm-2 carbon application on soil fertility index were about 16-17 years after the application of carbon to soil.In conclusion,this study found that the 1st,2nd,and 5th years of biochar aging could improve soil moisture and nutrients,and the optimization effect of 12 t·hm-2 carbon application was better than 6 t·hm-2 carbon application.However,as the years of aging and decomposition in the field increase,the effect of improving soil water,fertilizer and yield will decrease.Therefore,timely supplementing charcoal within the effective years of biochar can make the best,rational and efficient comprehensive utilization of biochar,which is a water-saving and fertilizer-saving solution.The best charcoal application mode for increasing yield. |
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