Winter wheat yield and water use efficiency response to organic fertilization in northern China: A meta-analysis

Nitrogen (N) application is a basic practice for increasing cereal yield and efficient utilization of N sources is key to sustainable intensification. A meta-analysis was conducted to determine how organic fertilization (i.e., livestock manure) affects yield, yield variability and water use efficiency (WUE) of winter wheat (Triticum aestivum L.) in northern China, and how this is impacted by N management and growing environment. Organic fertilization significantly increased grain yield and WUE by an average of 18 and 20 % compared to without organic fertilizer, respectively, and also reduced spatial and temporal yield variability. Compared to without organic fertilizer, change in grain yield was +24, +28, and −11 % for treatments of synthetic nitrogen fertilizer plus organic fertilizer with the same level of synthetic nitrogen (NOF), decreased level of synthetic nitrogen fertilizer combined with organic fertilizer (N_LOF), and a portion of synthetic nitrogen fertilizer replaced with organic nitrogen fertilizer at the same level of nitrogen (N_ROF), respectively. The positive effect of organic fertilizer on grain yield and WUE of winter wheat was greatest when yield levels was <4.0 Mg ha^–1. Moreover, organic fertilization was most effective at improving grain yield and WUE in North China Plain when synthetic N application was <150 kg N ha⁻¹ and in growing environments with SOM <1.4 % and ET <500 mm. These results demonstrate that applying organic fertilizer in combination with a decreased level of synthetic N fertilizer is an effective approach for advancing sustainable intensification of winter wheat in northern China, and that greatest benefits with organic fertilization may occur when local environmental factors (e.g., growing region and soil conditions) are appropriately considered.