Nitrogen Application Affects Grain Yield By Altering The Soil Moisture And Nitrate-N Of Maize/Wheat Cropping System In Dryland Areas Of Northwest China*

Few studies have investigated the effects of N application in a wheat/maize rotation system on soil moisture, residual nitrate-N (NR), growth, grain yield (GY) and nitrogen use efficiency (NUE) in northwest China under dryland conditions. A five-season (June 2013-October 2015) field experiment was conducted using N fertilizer rates of 0, 86, 172 and 258 kg ha(-1)during the summer maize growing season, and 0, 105, 210 and 315 kg ha(-1)during the winter wheat growing season. Soil NR increased sharply as N rates rose, but soil moisture storage decreased. Summer maize under the high N treatment suffered from increased NR levels and low soil water at the vegetative stage. The dry matter levels increased as the N supply rose during the wheat season. When the N application rate was below 210 and 172 kg N ha(-1)for wheat and maize, respectively, yield increased as the N application rose, but excessive N applications negatively affected maize and wheat grain yields. NUE decreased significantly as time progressed and N rates increased. The most appropriate N rates were 172 kg N ha(-1)for maize and 210 kg N ha(-1)for wheat, which led to relatively good soil moisture uptake and NR conditions.