Soil N transformation mechanisms can effectively conserve N in soil under saturated conditions compared to unsaturated conditions in subtropical China

文献类型： 外文期刊

第一作者： Zhang, Yushu

作者： Zhang, Yushu;Ding, Hong;Zheng, Xiangzhou;Zhang, Yushu;Cai, Zucong;Zhang, Jinbo;Zhang, Yushu;Misselbrook, Tom;Carswell, Alison;Cai, Zucong;Zhang, Jinbo;Cai, Zucong;Zhang, Jinbo;Muller, Christoph;Muller, Christoph

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关键词： N-15; N transformations; Nitrogen retention; Saturated soils

期刊名称：BIOLOGY AND FERTILITY OF SOILS （ 影响因子：6.432； 五年影响因子：6.332 ）

ISSN： 0178-2762

年卷期： 2018 年 54 卷 4 期

页码：

收录情况： SCI

摘要： The connection between moisture and nitrogen (N) transformation in soils is key to understanding N losses, particularly nitrate (NO3-) losses, and also provides a theoretical framework for appropriate water management in agricultural systems. Thus, we designed this study to provide a process-based background for management decision. We collected soil samples from the long-term field experiment in subtropical China, which was designed to examine tobacco and rice rotations under a subtropical monsoon climate. The field experiment was established in 2008 with four treatments: (1) no fertilization as control; (2) N, phosphorus (P), and potassium (K) fertilizers applied at recommended rates; (3) N fertilizers applied at rates 50% higher than the recommended amounts and P and K fertilizers applied at recommended rates; and (4) N, P, and K fertilizers applied at recommended rates with straw incorporated (NPKS). Soil samples were collected during the unsaturated tobacco-cropping season and saturated rice-cropping season and were incubated at 60% water holding capacity and under saturated conditions, respectively. Two N-15 tracing treatments ((NH4NO3)-N-15 and NH4 (NO3)-N-15) and a numerical modeling method were used to quantify N transformations and gross N dynamics. Autotrophic nitrification was stimulated by N fertilizer both under unsaturated and saturated conditions. The rate of NO3- consumption (via immobilization and denitrification) increased under the NPKS treatment under saturated conditions. Secondly, the rates of processes associated with ammonium (NH4+) cycling, including mineralization of organic N, NH4+ immobilization, and dissimilatory NO3- reduction to NH4+, were all increased under saturated conditions relative to unsaturated conditions, except for autotrophic nitrification. Consequently, NO3--N and NH4+-N concentrations were significantly lower under saturated conditions relative to unsaturated conditions, which resulted in reduced risks of N losses via runoff or leaching. Our results suggest that under saturated conditions, there is a soil N conservation mechanism which alleviates the potential risk of N losses by runoff or leaching.

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