Fallow season precipitation is a useful criterion to optimize nitrogen fertilizer for WUE and dryland winter wheat production

Abstract Precipitation is the major cause of yield variation in rainfed agriculture production on the Loess Plateau. Overfertilization is economically and environmentally undesirable. Optimizing N inputs according to fallow season precipitation (PF) is vital for efficient crop water use. An 8 year field experiment was conducted using 7 N rates to explore the prediction of PF on optimal N input for higher yield and water use efficiency (WUE). Reference range to describe years as normal (220.7–346.2 mm), dry ( 346.2 mm) based on 37-year precipitation. Optimum N rate varied with the PF and was 150, 150–180, and 210 kg ha−1 during dry, normal, and wet years. Maximum yield and WUE obtained by optimizing the N input was largely attributable to the increases in spike number per hectare. A non-linear regression showed that yield increased from 1.6-15 kg ha-1 with every mm increase in the PF and yield increased by 46 kg ha-1 with every 1% increase in the ratio of PF to total precipitation. Thus, dryland wheat yield may be improved by adjusting the nitrogen rate in accordance with PF in rainfed winter wheat farming systems.