Long-term N fertilization increases water use and use-efficiency of winter wheat

Abstract

Context

North China Plain (NCP) is characterized with sporadic seasonal rainfall patterns and scarce surface water resources that challenge the consistency of winter wheat production. Farmers in the NCP tend to fertilize crops with luxury N to obtain high yield, but such practices have accelerated depletion rates of scarce water supplies. However, the influences of long-term N treatments on water use and use-efficiency in the winter wheat production are still not fully understood, which is important for optimizing N rates and irrigation to promote agricultural green development.

Objective

The purpose of this study was to quantify the impacts of different N rates on water consumption and water use efficiency (WUE) in winter wheat using 11-year experimentation.

Methods

This study was focused on a winter wheat-summer maize cropping system in an 11-year field experiment in the NCP, which comprised five N rates in the wheat production season, namely 0, 60, 120, 180 and 240 kg N ha⁻¹, hereafter recorded as N0, N60, N120, N180 and N240, respectively.

Results

Fertilization longitudinally increased the yield and WUE of winter wheat, but also ramped water use. Water consumption and WUE under the N60-N240 treatments were 17–38 % and 186–333 % higher than that in the N0 treatment, respectively. Soil water extraction primarily occurred in the 0–120 cm soil depth, and which was predominantly concentrated within the 0–60 cm soil layer before flowering. It primarily reflected by root distribution abundance and yield formation. Greater yield and aboveground biomass under high N treatments were directly proportional to larger amount of water consumption in both vegetative and reproductive stages.

Conclusions

Increased N rates resulted in higher wheat yield and WUE but also caused larger amount of water consumption, while low N inputs significantly reduced water consumption but led to reduced WUE in the long-term. The optimal N rate to achieve high levels of wheat yield and WUE with low water consumption is 180 kg N ha⁻¹ (N180) in the study.

Implications

Application of N fertilizer is beneficial for improving WUE, however, N application may result in accelerated premature senescence when water is limiting, the appropriate N rates should thus consider soil water availability as well as potential for the crop to receive water from rainfall or irrigation.