半湿润农田生态系统长期施肥对土壤团聚体中有机氮组分的影响

通过对黄土高原半湿润农田生态系统25年的田间肥料定位试验,研究了长期不同施肥模式对土壤有机氮组分及其在各级团聚体中分布的影响.结果表明:长期施肥对水解氨态氮、水解未知氮在土壤各级团聚体中分布的影响最大,对氨基酸态氮的分布有一定影响,而对氨基糖态氮分布的影响较小.长期施用化肥和有机肥能有效地影响水解氨态氮和水解未知氮与团聚体的结合作用,而氨基糖态氮在土壤氮循环转化过程中具有较强的稳定性.长期施肥条件下土壤水解全氮与有机碳、全氮以及团聚体分形维数均呈极显著正相关,其r分别为0.942,0.981,0.910(P<0.001),说明土壤有机氮组分对土壤团聚体的形成和性质具有显著影响.相关分析表明,土壤全氮或有机质对1～2mm和0.25～1mm土壤团聚体中各有机氮组分的影响较大.

Effects of long-term fertilization on distribution of organic nitrogen components in soil aggregates in sub-humid agroecosystem

A 25-year long-term fertilization experiment was conducted on a Eun-Orthic Anthrosols in the sub-humid agroecosystem on Loess Plateau to study the effects of different fertilization on the distribution of organic nitrogen components in soil aggregates.The results indicated that under long-term fertilization,the distribution of hydrolyzed ammonia N and hydrolyzed unknown N(HUN)in soil aggregates was affected most significantly,followed by that of amino acid nitrogen,and of amino sugar nitrogen,suggesting that applying chemical and organic fertilizers in long-term could promote the combination of soil aggregates with hydrolyzed ammonia N and HUN,while amino sugar nitrogen was more stable during the processes of nitrogen cycling and transformation in soil.There were significant positive correlations of soil total hydrolyzed nitrogen with soil total organic carbon,total nitrogen,and fractal dimensions of aggregates,the correlation coefficient being 0.942,0.981 and 0.910,respectively,illustrating that soil organic nitrogen components had significant effects on the formation and characteristics of soil aggregates.Correlation analysis indicated that soil total N and organic C had greater effects on the organic nitrogen components in 1-2 mm and 0.25-1 mm soil aggregates.