Optimized fertilization based on fallow season precipitation and the Nutrient Expert system for dryland wheat reduced environmental risks and increased economic benefits

In drylands, optimized management of fertilization based on precipitation is very important to reduce fertilizer inputs and environmental risks and improve crop yield and benefits. Based on a four-year winter wheat experiment with two treatments (FP, farmers’ practices; NE, Nutrient Expert system recommendation) at nine counties of the Chinese Loess Plateau, we determined the effects of NE on wheat yield, environmental risks, and economic benefits under three precipitation year types (dry, normal, and wet) and recommended optimized N fertilization. The results showed that the NE treatment reduced N and P fertilizer input rates by 21.7% and 50.0%, respectively, Nr losses by 30.1% and GHG emissions by 21.6%, but it did not affect wheat grain yield compared to the FP treatment. There were no significant differences in N and P input rates among the three precipitation year types, but higher grain yield and partial factor productivity of N and P fertilizers were found in wet years in the NE treatment. Additionally, soil nitrate N residues in the 0–100 cm soil layers were ordered in wet years < normal years < dry years. Based on the NE system, the optimized N fertilization method could further reduce the N fertilizer rate by 16.6% and 62.5%, Nr losses by 20% and 68%, and GHG emissions by 1.7% and 47.8% in normal and dry years, respectively, but could increase economic benefits by 3.3% and 5.6%, suggesting that optimized fertilization based on fallow season precipitation can result in multiple benefits for agriculture and the environment.