Effects Of Mulching,Ridge Tillage Practices And Nitrogen On The Sustainability Of Spring Maize On The Loess Tableland

The Loess Plateau is a typical arid farming area and an important part of global agricultural system.The crop yield in this region is very important to ensure food security.The improvement of crop productivity was limited by the special climate condition and the lack of water and N nutrients in this area.Therefore,the conservation tillage,such as plastic film mulching,straw mulching and ridge tillage,have been widely applied in this area.However,there is a lack of systematic research on the agricultural sustainability of plastic film mulching,straw mulching and ridge tillage on the Loess Plateau.This study focused on spring maize,the main grain crop in the arid agricultural region of the Loess Plateau.A 6～year continuous field experiment was carried out in Changwu from2016～2021,to study the yield stability,water and N balance,the change of soil organic carbon and soil active nitrogen pool of spring maize under plastic film mulching,straw mulching and ridge tillage in arid areas of the Loess Plateau.The field experiment was conducted using a split plot design.The tillage systems investigated were:conventional tillage（CT）,ridge tillage（RT）,partial plastic mulching with conventional flat cultivation（FM）,ridge tillage with plastic film mulching on ridge（RTF）,and maize straw mulching（SM）.In combination with the tillage systems,two N application rates(0 and 225 kg N ha^–1)were used,providing a total of 10 treatments,each with three replicates.The main research results were as follows:1.The plastic film mulching combined with N fertilizer was an effective way to maintain high and stable yield.The results showed that plastic film mulching combined with N fertilizer significantly increased the yield and yield sustainability of spring maize,and decreased yield variability.Compared with CT,the yield of plastic film mulching combined with N fertilizer increased significantly by 65.0%to 73.4%,the yield sustainability index increased by 11.1%to 18.8%,and the yield variation coefficient decreased by 4.8%to 10.6%.The SM was significantly affected by N fertilizer and climate factors.The RT has limited yield increase and low yield sustainability.2.Soil evaporation was significantly reduced by plastic film mulching,canopy transpiration and canopy transpiration/evapotranspiration（T/ET）ratio was significantly improved by plastic film mulching combined with N fertilizer.The water consumption structure of maize was optimized under plastic film mulching.Thus,the water use efficiency was improved.Compared with CT,plastic film mulching combined with N significantly increased canopy transpiration by 15.9%～19.9%,T/ET ratio by 12%and water use efficiency by 58.8%～72.2%.Additionally,plastic film mulching combined with N fertilizer increased water consumption of spring maize and rainfall utilization potential,which may aggravate soil water deficit in normal water years.However,the results of six consecutive years showed that the rainfall in fallow seasons and humid years could replenish the soil water consumption of maize and maintain the soil water balance.Soil water deficit was not caused by plastic film mulching combined with N fertilizer.3.The plastic film mulching and straw mulching significantly improved the N uptake,reduced the residual N in soil and potential losses.The plastic film mulching and straw mulching significantly increased the N accumulation,and improved the N use efficiency.The results of labeled ¹⁵N showed that plastic film mulching and straw mulching significantly increased the seasonal N use efficiency by 8.2%～12.1%and the cumulative N use efficiency by 10.0%～16.4%.4.The results showed that plastic film mulching combined with N fertilizer could maintain or improve soil quality.The results showed that SM significantly increased soil organic carbon（SOC）content by 22.3%～33.3%and total nitrogen（TN）content by27.1%～29.8%.The plastic film mulching combined with N fertilizer could significantly increase SOC and TN content.Ridge tillage and CT had a tendency to reduce SOC and TN content.5.During the whole growth period,the ammonia flux in canopy was 0.001～0.116 kg N ha^–1d^–1,and accumulation of ammonia flux in canopy was 1.50～4.75 kg N ha^–1.Plastic film mulching significantly increased ammonia flux in canopy,while reduced soil ammonia flux and field ammonia flux,and decreased ammonia volatilization loss rate.Compared with CT,plastic film mulching significantly reduced the cumulative accumulation of soil flux by 22.2%～37.7%,cumulative accumulation of field by 16.5%～17.4%,and reduced ammonia emission coefficient by 0.94%～1.04%.6.Fertilizer nitrogen had a tendency to leak into deep layer year by year.The plastic film mulching reduced the leaching of mineral nitrogen to deep soil and reduced the risk of leaching loss.7.The N budget was negative under without N application.The consumption of soil nitrogen was accelerated under plastic film mulching.The SM alleviated soil nitrogen consumption.Nitrogen application replenished the consumption of original nitrogen in soil and maintained or increased the N content in soil.In conclusion,the mulching practices combined with N fertilizer could improve grain yield and yield sustainability,and reduce yield variability.The mulching practices combined with N fertilizer could improve water and N use efficiency.The SM and plastic film mulching combined with N fertilizer could increase SOC content,TN content and other soil nutrients,which is beneficial to maintain or improve soil quality.The yield increase effect of RT is limited,the yield variability was high.The SOC and TN contents under RT tended to decrease.Hence,plastic film mulching and straw mulching combined with N fertilizer application are effective choices for agricultural sustainable development in dryland farming areas,but attention should be paid to the microplastic pollution caused by plastic mulch and the epidemic of diseases and pests during straw returning.