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

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.