Analysis Of Nutrient Balance And Economic Benefit Under Different Nitrogen Fertilizer Operation Modes In Loess Plateau Spring Corn

Nitrogen is an important factor restricting the yield of spring maize in the dry Loess Tableland.In order to pursue high yield,excessive fertilization is common,which leads to the decrease of fertilization efficiency and the increase of soil nitrogen residue,resulting in fertilizer waste and soil pollution.Therefore,to study the nitrogen utilization,nitrogen balance and economic benefit of spring maize under different nitrogen management modes,combined with the research results of early soil nitrogen leaching resistance control,put forward scientific and reasonable nitrogen management measures,and provide scientific basis for guiding local spring maize production.The experiment was conducted for four years（April 2017 to October 2020）at Changwu Loess Plateau Agricultural Ecology Experimental Station of The Chinese Academy of Sciences in Changwu County,Shaanxi Province.The spring maize variety"Xianyu 335"was planted once a year with semi-plastic film mulching.A completely random block design was adopted and each treatment was repeated three times.There were four different contents:（1）The experiment of reducing nitrogen application:seven different nitrogen gradients were set based of the local farmers’traditional nitrogen application rate of 250 kg·hm^-2,which was successively reduced by 20%.（2）Straw deep buried test:straw deep burial was carried out on the basis of two different levels of nitrogen application of 200 kg·hm^-2 and 250 kg·hm^-2.（3）Nitrifying inhibitor test:nitrifying inhibitor（DCD）was added at 1%,5%,10%and 15%of nitrogen application rate on the basis of 200 kg·hm^-2 nitrogen application rate,respectively.（4）Slow and controlled release fertilizer experiment:under the total nitrogen application rate of 200 kg·hm^-2,different ratios of slow and controlled release fertilizer and ordinary urea were set,which were 65%+35%,50%+50%and 35%+65%,respectively.Corn yield,plant nitrogen content and soil ammonium nitrate nitrogen content were measured at the harvest stage of each season.The main conclusions are as follows:（1）In the range of 0 to 250 kg·hm^-2,with the increase of nitrogen application rate,the total nitrogen content and total nitrogen uptake of maize increased significantly,and the nitrogen use efficiency increased firstly and then decreased,and reached the maximum value when the nitrogen application rate was 200 kg·hm^-2.Nitrogen agronomic efficiency and nitrogen production efficiency were not positively correlated with nitrogen application rate,but were better under low nitrogen treatment.When N application rate was 200 kg·hm^-2,straw returning could not increase total N content of maize,but increasing straw deep burial could increase total N uptake,N use efficiency,N agronomic efficiency and N production efficiency of maize.The total nitrogen content of maize reached the maximum value when 50%controlled release urea+50%common urea was applied,the nitrogen use efficiency was the best when common urea was applied alone,and the agronomic efficiency and production efficiency of nitrogen fertilizer were the best when 65%controlled release urea+35%common urea was applied.When N application rate was 200 kg·hm^-2,total N content of maize increased significantly in the range of 5%～10%DCD.When DCD concentration was1%～10%,the total nitrogen uptake of maize increased with the increase of DCD concentration.When DCD concentration continued to increase,the total nitrogen uptake of maize decreased,and the nitrogen use efficiency decreased first and then increased with the increase of DCD concentration.When DCD concentration was in the range of 5%～10%,it reached the maximum value.The agronomic efficiency and production efficiency of nitrogen fertilizer increased first and then decreased.（2）With the increase of nitrogen application rate,the crop nitrogen removal increased significantly.When the nitrogen application rate was more than 200 kg·hm^-2,the soil residual nitrogen content increased significantly,and the soil nitrogen surplus reached the maximum value when the nitrogen application rate was 250 kg·hm^-2.Under the premise of high nitrogen application rate,increasing straw deep burial increased soil nitrogen residue and nitrogen surplus,and the total nitrogen input increased significantly with the increase of nitrogen application rate and residual mineral nitrogen in the previous year.The combined application of 50%controlled release urea+50%ordinary urea reduced the nitrogen content and the apparent loss of crops compared with that of ordinary urea alone.Increased application of nitrification inhibitors did not increase the total nitrogen input,nor significantly increased the amount of nitrogen taken out of crops,which would reduce the amount of nitrogen taken out of crops to a certain extent.However,soil nitrate nitrogen residue was significantly reduced.When DCD content was between 5%and 10%,the nitrogen surplus was relatively low.（3）In the range of 0 to 250 kg·hm^-2,the yield and economic benefit of spring maize increased firstly and then decreased with the increase of nitrogen application rate.When the nitrogen application rate was 200 kg·hm^-2,the yield and economic benefit were the highest.Under the traditional nitrogen application rate(N 250 kg·hm^-2),straw deep burial could effectively increase the yield and economic benefit of maize,while increasing straw deep burial could also increase the yield and economic benefit of maize at the N application rate of200 kg·hm^-2,but the difference was not significant.Common urea combined with slow and controlled release fertilizer can reduce maize yield and significantly reduce economic benefit and yield input ratio of maize.When N application rate was 200 kg·hm^-2,the yield increase effect was the best when DCD concentration was about 10%.Further increase of DCD dosage will cause corn yield reduction,and with the increase of DCD concentration,economic benefit and yield input ratio would be significantly reduced.