北方典型灌区不同灌期农田系统中氮素迁移特征分析

以内蒙古河套灌区杭锦后旗解放闸灌域为研究区,分析2009年夏灌和秋浇前后土壤中、浅层地下水和土壤渗滤液中的硝态氮、总氮的分布特征,研究不同灌期农田系统中氮素的迁移规律及其影响因素.结果表明:夏灌对氮素的稀释作用明显,反硝化作用也会降低地下水中硝态氮的浓度,此外玉米地块的氮流失在夏灌时相对明显;秋浇是农田氮素淋失的主要阶段,一方面是硝态氮 (NO3-N) 在灌水作用下向下淋失,另一方面是土壤中的NO3-N 在反硝化作用下转变成N2O、N2和O2释放;夏灌与秋浇两次灌水前后地下水中总氮 (TN) 的峰值滞后于NO3-N,表明氮素的流失除以NO3-N的形式发生之外,部分氨氮以及有机氮等其他形式的氮素在灌溉驱动下也发生一定程度的纵向流失.

Transfer characteristics of soil nitrogen in northern typical irrigation area under different irrigation periods

Nitrogen (N) is necessary element for crop growth, as well as an important factor of water eutrophication. In this paper, the Jiefangzha Irrigation District of Hetao Irrigation Zone of Inner Mongolia was chose as the study area to highlight the soil N circle during the irrigation periods. The distributions of total nitrogen (TN) and nitrate nitrogen (NN) in soil, shallow ground water and soil leachate during summer irrigation and autumn irrigation were analyzed. The results indicated that summer irrigation obliviously diluted the N, and denitrification in the groundwater lowered the concentration of NN, the corn field N loss relatively obviously after summer irrigation. Autumn irrigation was the main phase of nitrate loss in farmland. On the one side, the NN was leaching down under the watering; on the other side, the NN was released as the shape of N2O, N2 and O2 after denitrification. The peak value of TN in the groundwater lagged behind that of NN during both summer and autumn irrigation. It was conclude that included the loss of NN, partial NH4-N, organic N and some other forms of N had a certain extent lengthways leaching under the irrigations.