| Maize and wheat are the main food crops in the Loess Plateau,which play a vital role in ensuring food security and maintaining social stability in China.However,the problems in this region,such as labor shortage,high crop production cost,excessive nitrogen application and low nitrogen use efficiency,seriously affect the cultivation of maize and wheat,and have a certain impact on the environment.In order to explore the efficient cultivation techniques suitable for crop planting in the Loess Plateau and its effect on the environment,the field experiments of maize and wheat were designed in this study.In the experiment of high-efficiency cultivation of maize,nitrogen reduction,high density planting and one-time basal slow-release urea were compared with local conventional cultivation techniques.There had three treatments,the conventional treatment(the fertilizer rates was 225 kg N ha-1 which used common urea,2/5 base fertilizer and 3/5 topdressing,45000 plants·ha-1),the optimized treatment(substrate slow-release urea 180 kg N ha-1,one-time basal application,65000 plants ha-1)and the control(N0 45000 plants·ha-1).The agronomic effect,water and nitrogen utilization,environmental benefit and mechanical direct harvest index of spring maize were studied in these treatments.The high efficiency cultivation experiment of wheat was designed by split-plot experiment,The field experiment was a split-plot design,where in combination of two winter wheat varieties（Xiaoyan 22 and Zhengmai 366）as main factor and two N application rates(0 kg N ha-1,N0 and 180 kg N ha-1,N180)as sub factor were applied.The agronomic effects,nitrogen utilization and environmental benefits of winter wheat were studied in these treatments.The main results of these studies are as follows:（1）Compared with the conventional treatment,the optimized treatment significantly increased the grain yield,ear number per hectare,economic benefit and biomass of spring maize（P<0.05）,with increments of 4965 kg ha-1,23 million panicles·ha-1,10964￥ha-1 and11840 kg ha-1,respectively.The leaf area index of optimized treatment was significantly higher than that of conventional treatment at jointing stage,trumpet stage,silking stage and milk stage（P<0.05）,and the increments were 0.30,0.46,0.85 and 1.79,respectively.（2）Optimized treatment of spring maize significantly increased apparent nitrogen use efficiency and agronomic nitrogen efficiency.The nitrogen uptake of the optimized treatment was 52.68 kg N ha-1 higher than that of the conventional treatment（P<0.05）.The apparent nitrogen use efficiency and agronomic nitrogen efficiency of the optimized treatment were significantly higher than those of the conventional treatment（P<0.05）,and the increments were 23.41%and 31.25 kg kg-1,respectively.（3）Compared with the conventional treatment,the farmland water consumption and water use efficiency of the optimized treatment were significantly increased by 15.98 mm and 8.47 kg ha-1 mm1,respectively（P<0.05）.（4）Compared with Xiaoyan 22,Zhengmai 366 nitrogen application treatment significantly increased grain yield,1000-grain weight,grain nitrogen uptake,Agronomic nitrogen efficiency and Physiological nitrogen efficiency by 857 kg ha-1,1.16 g,38.2 kg N ha-1,4.98 kg kg-1 and 9.66 kg kg-1,respectively.（5）The whole growing season about spring maize accumulation of ammonia volatilization in soil,canopy and field were 2.876～3.562 kg N ha-1,6.314～8.178 kg N ha-1and 9.190～11.583 kg N ha-1,respectively.The whole growing season about winter wheat accumulation of ammonia volatilization in soil,canopy and field were 11.503～16.640 kg N ha-1,-1.436～0.784 kg N ha-1 and 11.948～15.204 kg N ha-1,seperately.Conclusion:Optimized cultivation（substrate slow-release urea 180 kg N ha-1,one-time basal application,65000 plants ha-1）can reduce fertilization times,save fertilizer,increase yield and save cost,and improve nitrogen use efficiency and water use efficiency,so it is suitable to be popularized in spring maize planting area of loess plateau. |
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