Integrated nitrogen fertilizer management for improving wheat yield and the efficiency of water and nitrogen fertilizer use

Improving resource use efficiency through optimized nitrogen (N) management is the key to increasing crop productivity, but it remains unclear whether integrated N management practices could better improve wheat yield and the use of N and water. Here we investigated the effects of individual and integrated N management practices on wheat production in different soil-climatic conditions, and constructed the relationship between the soil-climate factors and N application rate on wheat yield. Results showed that individual N management practice (optimized N application rate only) reduced wheat yield by 2.4 %, increased N use efficiency (NUE) by 45 %, and decreased water use efficiency (WUE) by 2.2 %; however, integrated N management practice (integrating optimized N rate with irrigation, tillage, manure, or straw return) increased yield and NUE on average by 5.4 % and 55 % respectively, without reducing WUE. In different soil-climate conditions, individual N management practice decreased wheat yield from 1.1 % to 5.0 %; however, integrated N management practice increased yield by 8.5 %, 6.4 %, and 5.8 % in soil organic carbon (SOC) >= 10 g kg(-1), mean annual precipitation <= 400 mm, and 10 degrees C < mean annual temperature <= 15 degrees C, respectively. Mixed-effects model showed that the integrated N management practice had a higher yield by better exploiting the yield-enhancing benefits of SOC. Facing the complex production environment of the future, applying integrated N management practice will be a key alternative for improving grain production and resource use efficiency.