Study On Three-Nitrogen Transport And Transformation Law In Unsaturated Zone Of Red Paddy Soil

This thesis is mainly about the transportation and transition regulation of nitrogen in unsaturated zone. Ammonia-nitrogen, nitrite-nitrogen and nitrate- nitrogen are used as the research object, combining with collection of soil solution regularly and monitoring. The site of this research locates in the rice fields of the agricultural ecosystem located in Qianyanzhou, Jiangxi. The scientific basis will be provided for prediction and quantitative assessment of the nitrogen pollution in groundwater. The test results show that the content of ammonia-nitrogen is low during the period of early rice, while nitrite-nitrogen and nitrate- nitrogen are high obviously. The nitration reaction is inhibited during the period of late rice, then ammonia-nitrogen are high obviously. As time increases, ammonia-nitrogen tends gradually dynamic equilibrium. Three-nitrogen at different depths in water has obvious characteristics of migration. The content of ammonia-nitrogen is highest in the soil solution during 40~120cm, the content of ammonia- nitrogen rises at first, then decreases during 20~120cm, and the content of nitrate-nitrogen decreases gradually with depth's increase because of denitrification consumption. The major concentration field bits of iron and manganese affecting nitrogen transport and transformation is identified in the unsaturated zone. There is a significant positive correlation between the content of iron and manganese in the depth of 120cm, the change of nitrogen is controlled significantly by iron and manganese concentration field. The content of nitrogen, iron and manganese has a rather poor correlation in other depths. The content of ammonia-nitrogen and nitrite-nitrogen has a significantly positive correlation with iron and manganese, and nitrate-nitrogen content has a significantly negative correlation with iron and manganese.