长期施肥对黄土旱塬黑垆土有机氮和有机碳的影响

Response of Soil Organic Nitrogen Forms and Organic Carbon to Long-term Fertilization in Dry Highland of Loess Plateau

耕地土壤中的氮素和有机碳是土壤肥力高低的指标,其含量除受各种自然因素影响外,还强烈地受到施肥的影响。为揭示施肥对土壤供氮潜力和有机碳的影响,本文采用Bremner法对20a长期定位试验的黑垆土耕层土壤有机氮组成进行了分级。结果表明,单施氮肥或磷肥对耕层土壤全氮、各形态有机氮的绝对含量及其占全氮的相对比例均无显著影响;有机肥和化肥配施,显著提高了耕层土壤全氮、酸解有机氮、酸解铵态氮、氨基酸态氮的含量,其中对氨基酸态氮的影响最大。施化肥或有机肥均能显著提高有机碳水平,有机无机肥配施效果最好。在不同肥料处理中,土壤各种形态有机氮的含量高低顺序依次为:酸解铵态氮>氨基酸态氮>酸解未知态氮>氨基糖态氮。长期有机无机肥配施显著提高了土壤供氮潜力和有机质水平,是维持土壤肥力最优的施肥方式。

Soil organic nitrogen （N） and organic carbon （C） are important indicators of soil fertility, which are affected by natural factors and fertilization practices. The changes of N supply capacity and organic C in Isohumosols from dry highland of Loess Plateau after 20-year fertilization treatments were studied in this paper. The Bremner method was employed to analyze soil organic N fractionation. Compared with the control （CK）, N fertilizer or phosphorus fertilizer alone did not significantly affect quantity or composition of organic N forms. Application of manure plus mineral fertilizer significantly increased the total N（TN） （P〈O.05）, hydrolysable organic N, ammonium N and amino acid N in the soil increasing by 42.1%, 51.8%, 48.6%, 69.2%, respectively. Application of mineral fertilizer or manure, especially application manure plus mineral fertilizer increased organic C significantly. The contents of different forms of soil organic N in all treatments followed the order： ammonium N 〉 amino acid N 〉 non-hydrolysable N 〉 unidentified hydrolysable N 〉 amino sugar N. Manure plus mineral fertilizer increased the content of TN, most organic N and organic C, and was considered the best way for maintaining the soil fertility and sustainable agriculture.