长期施用不同肥料的土壤有机氮组分变化特征

采用Bremner有机氮分级方法研究了30年施用不同肥料的长期定位试验耕层土壤有机氮组分变化特征。结果表明,与不施肥(CK)处理相比,长期施用不同肥料均提高了耕层土壤全氮和有机氮含量,所增加的有机氮中酸解性氮和非酸解性氮各占一半左右,其中增加的酸解性氮有69.0%为未知态氮,21.0%为氨基酸氮,6.6%为氨基糖氮,3.4%为氨态氮。与单施化肥(NPK)相比,牛粪/稻草与化肥配施能进一步提高土壤全氮和有机氮含量,但是不同种类的有机肥与化肥配施所增加有机氮的组分有明显差异;其中牛粪与化肥配施处理(NPKM)所增加的有机氮有60.0%为酸解性氮,而稻草与化肥配施处理(NPKS)中所增加的有机氮有71.7%为非酸解性氮。牛粪与化肥长期配施有利于提高土壤酸解性氮含量,而稻草与化肥配施则有利于提高非酸解性氮含量。

Characteristics of Organic Nitrogen Fractions in Soils Under Long-term Different Fertilization

A better understanding of organic nitrogen(N) fractions in soils under long-term fertilization is critical to the regulation of N fertilizers and eco-environmental quality. In this study, a organic N fractionation method by Bremner was used to examine the characteristics of soil organic N fractions under long-term applications of different fertilizers. Compared to no fertilizer(CK) treatment, total N and organic-N in soils increased under long-term fertilization. About half of the increased organic-N was acid-hydrolysable N and the rest was non-acid hydrolysable N. Of the increased acid hydrolysable N, hydrolysable unidentified N, amino acid N, amino sugar N and ammonia N accounted for about 69.0%, 21.0%, 6.6%, and 3.4%, respectively. Total N and organic-N in the soils applied with organic fertilizers plus chemical fertilizers were higher than those with chemical fertilizer alone. However, organic-N fractions changed differently under different organic fertilizers. In the soils applied with cattle manure combined with chemical fertilizers(NPKM), about 60.0% of the increased organic-N was acid-hydrolysable N, while 71.7% was non-acid hydrolysable N in the soils with straw plus chemical fertilizers(NPKS). These results indicate that the composition of organic materials would have great impact on the fractions and availability of organic N in soils.