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作 者 ：申小冉 徐明岗 张文菊 吕家珑 王伯仁 蔡泽江

期 刊 ：植物营养与肥料学报 2012年 18卷 5期 页码：1133-1140

关键词：长期施肥；红壤；土壤颗粒；氮分配；

Keywords:long-term fertilization, red soil, soil particles, nitrogen distribution,

摘 要 ：土壤培肥过程中氮素的积累和在各级土壤颗粒中的分配对了解土壤氮素积累机制和氮素的可持续管理具有重要意义。本研究以红壤旱地长期定位试验为基础，采用离心法分离土壤颗粒，通过分析氮素在土壤不同颗粒中的含量，研究长期施肥对土壤中不同粒级土壤氮的分配的影响。结果表明，施肥二十年后，在0—20 cm土层，施肥处理的全氮含量在1.19~1.98 g/kg 之间，施肥处理全氮含量显著高于不施肥处理（CK）。在20—40 cm土层，土壤全氮含量分布在0.59~0.84 g/kg之间，显著低于表层土壤氮含量; 在0—20 cm土层，与氮磷钾化肥配施处理（NPK）相比，单施或者配施有机肥的土壤与砂粒、 粗粉粒、 细粉粒、 粘粒结合的氮含量分别提高220%、 84%、 46%和26%。而在20—40 cm土层，与NPK处理相比，有机肥的施用仅提高了与细粉粒、 粘粒结合的氮含量，降低了与粗粉粒结合的氮含量; 在0—20 cm土层中，红壤氮素主要分布在粘粒中。20—40 cm土层CK、 NPK和氮磷钾配施加秸秆还田处理（NPKS）表现为与粗粉粒结合的氮的分配比例最高，而施用有机肥的处理氮素分布仍以粘粒占比例最高。相关分析表明，土壤表层＜5 μm粒级的土壤颗粒中氮含量和作物的经济产量呈显著性正相关。长期施用有机肥可以显著提高表层土壤全氮及与各个颗粒结合氮的含量，不同处理的氮主要保存在粘粒中。而亚表层土壤中，施化肥或者秸秆还田加速了粘粒结合态氮的耗竭，配施有机肥促进了氮在粘粒中的积累，也更有利于土壤全氮的积累，是可持续的氮素管理措施。

Abstract:Accumulation and distribution mechanism of nitrogen in soil particlesize during soil fertility development is of great significance for sustainable agricultural management practices. Based on the longterm fertilization experiment, soil particlesize fractionation was separated by supersonic and centrifugation to explore the impact of longterm fertilization on the soil nitrogen concentration and distribution. Results showed that, after twenty years of fertilization, total nitrogen concentration (TN) under all treatments ranged from 1.19 g/kg to 1.98 g/kg in the 0-20 cm layer. Compared to the CK, TN was increased significantly under all treatments. At the 20-40 cm soil layer, TN varied from 0.59 g/kg to 0.84 g/kg for all treatments, which was obviously lower than that of the 0-20 cm surface soil; Nitrogen concentration in the sand, coarse silt, fine silt, and clay particlesize fractions for the treatments combined with manure were increased by 220%, 84%, 46%, and 26% compared to the NPK treatment with the same amount of nitrogen fertilizer in 0-20 cm soil layer. In 20-40 cm soil layer, compared to the NPK, nitrogen concentration in finesilt and clay particles were improved, whereas nitrogen concentration declined in coarsesilt particles under the treatments combined with organic manure; Soil nitrogen mainly associated with clay particles under the 0-20 cm layer. While in the 20-40 cm layer, there was much higher proportion of nitrogen associated with coarsesilt fraction under the CK, NPK and NPKS, clay particle contained the main part of nitrogen under the treatments with organic manure. There was significant positive linear correlation between crop grain yield and soil nitrogen concentration in the < 5 μm size fractions under top soil. In 0-20 cm layer, application of organic manure can significantly increase soil nitrogen concentration in bulk soil and particlesize fractions. Soil nitrogen was mainly associated with clay particle in red upland soil for all the treatments. In the 20-40 cm soil layer, application of mineral fertilizers with and without straw incorporation has no effects on nitrogen accumulation in clay size faction. Manure application greatly promotes the nitrogen accumulation in clay size fraction, acting as a sustainable soil nitrogen management practice.

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