中文摘要：

【目的】揭示施肥对土壤供氮潜力的影响。【方法】以土壤有机氮作为土壤肥力的重要指标采用Bremner法对棕壤29年长期定位试验的有机氮组成进行分级。【结果】单施化肥处理对耕层土壤有机氮含量及其组成无明显影响；有机肥和化肥配施，耕层土壤各形态酸解有机氮的含量都有不同程度的提高，其中氨基酸态氮的增加最为明显。在不同施肥处理中的顺序是氨基酸态氮〉非酸解态氮〉酸解氨态氮〉酸解未知态氮〉氨基糖态氮。各形态有机氮的剖面分布相似，含量均随土层的加深而降低。不同处理对有机氮各组分含量变化的作用表现为有机无机配施处理〉单施有机肥处理〉单施化肥处理、不施肥处理。【结论】长期有机无机肥配施显著提高了土壤的供氮潜力，是维持土壤肥力最优的施肥方式。

英文摘要：

[ Objective ] Soil organic nitrogen （N） is the main form of soil nitrogen, which is affected by fertilization practices. [Method] The Bremner method was employed to analyze soil organic N fractionation. After 29-year fertilization treatments, the changes of N supply capacity in a brown soil were studied in this paper. [Result] Compared with the control, neither single chemical fertilizer had the effect on the content of soil organic N, nor had the effect on the nitrogen composition. Application of manure with chemical fertilizer significantly increased the contents of all forms of hydrolysable organic N, especially the content of amino acid N. The contents of different forms of soil organic N in all treatments followed the order of amino acid N 〉 non-hydrolysable N〉ammonia N〉unidentified hydrolysable N〉amino sugar N. The distributions of all forms of organic＇N were similar, and decreased with layers＇ depth. The basic rule is organic-inorganic fertilizer treatment〉single organic manure fertilizer treatment〉single chemical fertilizer treatment and the control. [Conclusion] Manure plus chemical fertilizer increased the content of most organic N, and was considered the best way for maintaining the soil fertility and sustainable agriculture.