江苏句容水库农业流域农田土壤反硝化作用的研究

2008年6月、8月、12月和2009年3月，在江苏句容水库农业流域采集农田原状土壤样品，使用乙炔抑制实验室培养法测定土壤的反硝化速率，同时测定土壤的含水率、铵态氮（NH2-N）和硝态氮（NO_3-N）的含量，研究农田土壤反硝化速率变化、影响因素及其对流域氮损失的贡献。结果显示，旱地土壤反硝化速率范围在0．13-51．96kgN·hm^-2a^-1之间，水田土壤的反硝化速率范围在3．16-12．29kgN·hm^-2a^-1之间。相关分析表明，反硝化速率与土壤硝态氮（NO_3-N）浓度、铵态氮（NH2-N）浓度之间不具有显著相关关系；在12月和3月，反硝化速率与土壤含水率之间有显著相关关系，其他月份无显著相关关系。流域内农田土壤反硝化损失的总氮量为31．93tN·a^-1低于流域施氮总量的3．19％，可见，反硝化作用不是该流域氮损失的主要途径。

Denitrification of Farmland Soils in the Agricultural Watershed of Jurong Reservoir, Jiangsu Province, China

The seasonal variations in denitrification rate and corresponding nitrogn loss in the farmland soils were determined. Soil samples were collected from 29 different fields, including upland and paddy, in the agricultural watershed of Jurong reservoir, Jiangsu Province, between June 2008 and March 2009. The denitrification rates were analyzed using acetylene inhibition procedure, and concentrations of NH^＋4-N and NO_3-N were measured with spectrophotometric method. The results showed that denitrification rates ranged from 0.13 kgNhm^-2·a^-1 to 51.96 kgN·hm^-2·a^-1 for the upland and from 3.16 kgN·hm^-2.a·^-1 to12.29 kgN.hm·^-2.a^-1for the paddy. There was no significant correlation between denitrification rates and NH_＋4-N and NO_3-N concentrations in all soils. However, denitrification rates were significantly related to soil water content in the winter season （December and March）, but not for the summer season （June and August）. The total nitrogen loss amount was 31.93 tN·a^-l, much less than 1 000 tN·a^-1of total nitrogen fertilizer application amount, indicating that denitrification may not the main way of nitrozen loss in such a watershed.