Yield and N use efficiency of a maize-wheat cropping system as affected by different fertilizer management strategies in a farmer's field of the North China Plain

This study aimed to identify whether nitrogen (N) use efficiency in a summer-maize/winter-wheat double-cropping system of the North China Plain (NCP) could be increased by adjusting N supply to crop N demand, and through the use of alternate N fertilizers and application strategies. In a static experiment conducted on a farmers' field six reduced N treatments were compared to farmers' practice (FP: 550 kg (N) ha(-1) a(-1)) and a control treatment (CK). With few exceptions of single treatments in single cropping-seasons, the optimized fertilization of N did not lead to a yield reduction of either summer-maize or winter-wheat. The grain yield of summer-maize ranged between 5.8 and 7.1 Mg ha(-1). The grain yield of wheat ranged between 4.4 and 6.2 Mg ha(-1). For the first two vegetation periods of summer-maize, the recovery efficiency (REN: 0.09-0.30 kg kg(-1)) and agronomic efficiency of N (AE(N)) were mainly affected by the yield achieved in the control treatment (5.7 and 5.9 Mg ha(-1)), which was not significantly reduced compared to most fertilized treatments. In the third vegetation period of summer-maize, an increase of REN of the reduced treatments (0.37-0.58 kg kg(-1)) was determined compared to FP (0.21 kg kg(-1)). In both vegetation periods of wheat REN of the reduced treatments (0.34-1.0 kg kg(-1)) was significantly higher compared to FP (0.26 and 0.27 kg kg(-1)). The highest cumulated AEN, as well as cumulated grain yields were observed when ammonium sulphate nitrate +3,4-dimethylpyrazolephosphate (ASN(DMPP)) was applied according to crop N demand and residual soil mineral N. The highest REN was observed when urea ammonium nitrate was applied in a shallow, banded depot (UAN(DEP)). This research demonstrates that N application rates in a maize/wheat double cropping system may be significantly reduced compared to common farmers' practice, without negatively affecting grain yield, thereby increasing N use efficiency. (C) 2015 Elsevier B.V. All rights reserved.