Performance of a optimized nutrient management system for double-cropped wheat–maize rotations in North Central China

Over-application of nitrogen (N) and phosphorus (P), and insufficient supply of potassium (K) are considered primary reasons for restriction of yield improvement in North China Plain. Optimized nutrient management practices that are based on soil testing and yield targets have been developed. Other large scale field experiments have indicated that additional improvement for yield and nutrient use benefits is needed. The objective of this study was to evaluate the effects of the optimized nutrient management system on yield, nutrient uptake, nutrient utilization and profit in the North China provinces of Shanxi, Hebei, Shandong and Henan. Treatments consisted of a check without fertilizer use (CK), a balanced ‘optimum’ nutrient application (OPT), the farmers’ practice (FP), and a series of nutrient omission treatments (minus N, P and K, respectively). The results indicated that the OPT optimized grain yield, nutrient use efficiency, and profitability. Maize (Zea mays L.) yield increased by 12.2% at Shanxi and 18.5% at Hebei, respectively. Inputs of N and P across the wheat (Triticum aestivum L.) and maize system at the four sites was reduced by 13% (266 kg N ha^–1) and 45% (430 kg P₂O₅ ha^–1), while K input was increased by 43% (265 kg K₂O ha^–1). The OPT improved both measurements of nitrogen use efficiency; agronomic nitrogen efficiency (AE_N) and nitrogen recovery efficiency (RE_N) in the majority of cases. Although the OPT tested in this study increased yields and nutrient uptake, there remains considerable potential to improve AE_N and RE_N further for this intensive wheat–summer rotation system.