Recovery of residual fertilizer-nitrogen by wheat in a winter wheat–summer maize rotation in the north china plain: A soil column study
Cropping systems is potentially useful practice for mitigating nitrate leaching and increasing nitrogen use efficiency (NUE) because deeper rooted crops could capture the leached N from previous shallower rooted crops. The recovery of fertilizer nitrogen (FN) applied to maize (Zea mays L.) by the succeeding wheat (Triticum aestivum L.) in a winter wheat–summer maize rotation in North China Plain (NCP) was studied in 2003–2004 and 2005–2006 by creating 15N-labeled soil columns. We found that the in-season maize plant use efficiency of FN was about 46 to 48% and the total residual fertilizer nitrogen (RFN) in a 2-m soil profile at maize harvest was 34% in 2003–2004 and 41% in 2005–2006, the ratios of FN unaccounted for were about 19 and 12%, respectively. The RFN declined significantly down the soil profile. About 13 and 10% of total RFN, or 4.4 and 4.0% of total applied FN were observed below the 1.2 m soil depth. Wheat was able to recover the RFN up to the 2.0-m soil depth, the recovery ratio from upper soil layers was higher than that from lower layers and ranged from 4.4 to 23% in 2003–2004 and 4.6 to 34% in 2005–2006. Corresponding total recovery ratios were 13.7 and 21.4% of total RFN, or 4.9 and 8.7% of total applied FN, respectively. The annual recovery ratios were 51.6% in 2003–2004 and 56.2% in 2005–2006. The deep-rooting characteristics of winter wheat for deep N uptake should be taken as an important index in N fertilizer management in the rotation system.