Study On The Synergistic Mechanism Of Carbon And Nitrogen Enhancement In Agricultural Soils Under Maize Straw Return And Nitrogen Fertilizer Transport

The low utilisation of straw on the Loess Plateau of Inner Mongolia and the reality that the unreasonable distribution of nitrogen fertiliser from straw to field is a major factor in the waste of agricultural resources and the decline in sustainable productivity of farmland in the region.With the effective promotion of straw repatriation technology,how to regulate and optimise the application of nitrogen on the basis of straw repatriation to ensure the efficient use of straw resources has become a hot spot for agricultural research in the region.In this study,the effects of five different tillage practices on soil carbon sequestration,soil nitrogen accumulation,soil enzyme activity,plant material accumulation,leaf area index,leaf photosynthetic performance and yield of maize farmland were compared and analysed through two consecutive years of field trials,to elucidate the synergistic mechanisms and changes of soil carbon and nitrogen,and to reveal the effects of straw return and nitrogen fertilizer management on soil carbon and nitrogen.This study will provide a scientific basis for the research and development of efficient straw return technology for maize on the Loess Plateau of Inner Mongolia.The results are as follows:1.Straw return and nitrogen fertiliser transport had a greater effect on the soil reactive carbon fraction,with no difference in the effect of total soil organic carbon.Compared with the control FN,the HNS treatment significantly increased the soil soluble organic carbon content,the RNS treatment increased the soil easily oxidized organic carbon content by12.68-21.53%,and the soil microbial carbon content increased by 7.40-8.10%,indicating that nitrogen fertilizer post-fertilizer forward application with straw return can increase the effectiveness of soil organic carbon and sequester the soil carbon pool.2.Different nitrogen fertilizer transport methods under straw return conditions have a greater impact on soil nitrogen,HNS treatment soil total nitrogen,alkaline nitrogen and microbial nitrogen content significantly increased,RNS treatment can reach the HNS treatment nitrogen elevated level,and nitrogen fertilizer forward application with straw return can increase the accumulation of nitrate nitrogen and ammonium nitrogen in the cultivated soil layer,significantly reduce the leaching of mineral nitrogen.3.Straw return and nitrogen fertilizer transport significantly increased soil enzyme activity,RNS treatment soil catalase,soil urease,soil sucrase,soil alkaline phosphatase activity than the FN increased 20.66% to 27.81%,19.12% to 22.54%,34.69% to 39.14%and 30.44% to 45.53% respectively.Soil enzyme activity was better with N fertilizer postfertilizer forward application with straw return than with N fertilizer habitual application with straw return,and could reach the level of high N fertilizer application with straw return.4.Straw return and nitrogen fertilizer transport promoted maize growth,increased the upper ground dry matter accumulation and leaf area index,but there was no difference in the effect of each tillage method on maize plant height,RNS treatment maize leaf photosynthetic performance improved significantly,no significant difference between RN and FN treatment base without return treatment,leaf water vapour pressure deficit was not significantly different between treatments.5.In terms of yield and nitrogen fertilizer utilization,the FNS,HNS and RNS treatments increased by 3.20 to 5.30%,10.93 to 18.10% and 11.41 to 20.07% respectively compared to the control FN.Nitrogen fertilizer post-fertilizer forward application with straw return maize yield can reach the high amount of N fertilizer dispensing level,and the constant input of N fertilizer can obtain high nitrogen fertilizer bias productivity.In summary,straw return with nitrogen fertiliser transport can significantly improve soil carbon and nitrogen content,maintain the stability of soil carbon pool and increase soil nitrogen accumulation,improve soil enzyme activity,as well as promote crop growth and increase crop yield.In particular,the best performance was achieved by the forward application of nitrogen fertiliser with straw return,which can be used as a model for saving nitrogen,stabilising yields and increasing efficiency of straw return on the Loess Plateau of Inner Mongolia.