The Effect Of Film Mulching And Nitrogen Application On Nitrogen Balance And Water And Nitrogen Utilization Efficiency In Summer Maize

Maize is an important grain crop in the northwest of China.However,during the growth and development of maize production,there are problems such as imbalance between precipitation distribution and crop water demand and excessive application of nitrogen fertilizer leading to reduced water and fertilizer use efficiency and environmental pollution.Conventional cultivation methods are difficult to achieve high yield and efficient agricultural production.To solve the problems of water shortage and low utilization of nitrogen fertilizer in summer maize growing areas in northwest China,it is important to investigate planting strategies to improve the efficiency of precipitation resources,heat and nitrogen fertilizer utilization and reduce environmental pollution in summer maize growing areas,in order to achieve green and high-yielding and efficient production in dryland agriculture.This study was conducted in subhumid and prone arid region,with summer maize as the research object.Three mulching methods（FRM:furrow-ridge planting with full film mulching,FFM:flat planting with full film mulching,FNM:flat planting without mulching）were set up.Four nitrogen application levels（N100:100 kg N/hm²,N150:150 kg N/hm²,N200:200 kg N/hm²,N300:300 kg N/hm²）were set under FRM and FFM planting methods,and two nitrogen levels（N0:no N,N300:300 kg N/hm²）were set under FNM as control treatments.The effects of mulching and nitrogen application on physiological growth,nitrogen balance,yield,economic benefit and water and nitrogen use efficiency of summer maize were investigated to explore the green and high-yielding and efficient mulching and nitrogen application pattern of summer maize.The main research results were as follows:（1）Mulching is effective in increasing soil temperature from 0-30 cm and soil water storage from 0-100 cm.However,the effect of mulching on increasing 0-30 cm soil temperature（except for N300 under FFM）decreased from the nodulation stage onwards,and the warming effect decreased with increasing soil depth.FFM was more effective than FRM in increasing temperature（except at seedling stage）and FRM was more effective than FFM in increasing soil water storage in summer maize（except at filling stage）.Nitrogen application reduced soil water storage from 0-100 cm and increased with increasing nitrogen application,but had no significant effect on the soil temperature of 0-20 cm,which generally appeared to decrease with increasing nitrogen application.（2）Mulching significantly increased summer maize plant height,leaf area index and above-ground dry matter mass,chlorophyll content and net photosynthetic rate.FRM significantly improved the physiological indicators of summer maize growth compared to FFM,including the onset of rapid dry matter accumulation（T₁）by 1-4 d,the extension of the rapid dry matter growth period（T）by 1-4 d and the increase in V_max by 0.5%-8.9%,which facilitated the accumulation of dry matter by FRM.Plant height and above-ground dry matter mass and net photosynthetic rate both tended to increase and then decrease with increasing nitrogen application,and reached a maximum at 200 kg N/hm² under both FFM and FRM cropping methods.（3）Mulching significantly increased soil mineral nitrogen accumulation and enhanced nitrogen export from summer maize.Mulching（FFM and FRM）increased N export by an average of 35.4%compared to FNM.0-100 cm soil nitrogen leaching was significantly reduced by 13.7%-37.7%and plant nitrogen uptake was increased by4.9%-18.5%in FRM compared to FFM,but plant nitrogen uptake did not differ significantly between the 2 mulching treatments.In addition,cumulative NH₃volatilization was reduced by 0.13-23.83 kg/hm² in FRM compared to FFM,but cumulative N₂O emissions only increased by 0.05-0.12 kg/hm².Nitrogen balance under mulching was all nitrogen deficit,which was significantly reduced with increasing N application.The nitrogen deficit under FRM was significantly lower than under FFM,by 0.1%-25.2%,but NH₃ volatilization,N₂O emissions,soil mineral nitrogen accumulation,residues and nitrogen leaching all increased significantly.（4）Mulching and increasing nitrogen application improved yield components and increased yield and economic benefit of summer maize to different degrees,with FRM increasing yield by 6.0%-19.9%and net benefit by 6.3%-27.7%compared to FFM.Seed yield and net benefit all tended to increase and then decrease with increasing N application,reaching a maximum under the N200 treatment,but not significantly different from N300.（5）Compared with traditional flat crop,cover cropping（FFM and FRM）significantly reduced water consumption by 5.4%-15.4%,increased water use efficiency by 8.0%-43.6%and nitrogen fertilizer bias productivity by 2.2%-21.5%throughout the summer maize reproductive period,and FRM was more effective than FFM in improving water and nitrogen use efficiency.With increasing nitrogen application,water use efficiency,nitrogen use efficiency（except FFM）and nitrogen harvest index basically tended to increase and then decrease with increasing nitrogen application,while significantly reducing nitrogen fertilizer bias productivity.Under FRM cropping,the 200 kg N/hm² treatment had the highest water use efficiency and nitrogen harvest index,and the 150 kg N/hm² treatment had the highest nitrogen use efficiency.（6）By analyzing the results of fitting nitrogen application to yield,water use efficiency,nitrogen harvest index and gaseous nitrogen（N₂O and NH₃）emissions under mulch cropping（FFM and FRM）,it was determined that using FRM cropping with nitrogen application of 198 kg N/hm² was a suitable mulch nitrogen application pattern for summer maize in the semi-humid and drought-prone areas of northwest China.The mulching（FFM and FRM）provided a suitable soil water and heat environment for summer maize growth and promoted the accumulation of dry matter,resulting in a significant increase in yield and economic benefit.Seed yield was significantly higher by 198-1971 kg/hm² and economic benefit by 309-3527 RMB/hm²compared with traditional flat crop（FNM）,reflecting the high yield and efficiency of the mulching pattern.In addition,through the multi-objective optimization of nitrogen application rate under the two mulching planting methods,the green,high-yield,and high-efficiency mulching nitrogen application pattern for summer maize was determined in the northwest arid region.