河套灌区不同灌季土壤氮素时空分布特征分析

以内蒙古河套灌区东段乌拉特灌域为研究区,在春灌、夏灌和秋浇(2005年4月、7月和11月)3个不同特征灌季进行采样分析,应用传统统计学方法和地统计学中的普通 kriging 法,对研究区0～20cm土壤中氮污染物的空间分布特征进行了研究.结果表明,不同灌溉时期土壤中总氮、铵态氮和硝态氮的理论变异函数模型主要为球状、高斯和指数模型,与实际变异函数间的残差平方和在0.0009与0.1238之间,拟合效果较好;除11月铵态氮具有中等空间相关性外.其它参数均具有强烈的空间相关性;在4、7月土壤中总氮元素含量大体表现为东北高、西南低;研究区整体土壤总氮和硝态氮含量4月最高、11月最低,土壤铵态氮含量7月最高、11月最低.土壤中氮元素的上述时空变异受研究区地下水位、引水和农田排水不同期变化具有较大的影响.

Temporal and spatial variability of nitrogen in soil in the Wulate irrigation district of the Hetao irrigation area in Inner Mongolia

The spatial variability of nitrogenous pollutants in soil has a great significance for the balance of field fertilization and the decrease in the loss of nitrogen. After analysis of soil samples collected from the Wulate irrigation district, a case study area in the east of the Hetao irrigation area, traditional statistics and the ordinary Kriging method of geostatistics were applied to determine the spatial distribution of nitrogen in soil (total nitrogen, ammonia nitrogen and nitrate nitrogen) within a depth of 0 to 20 cm. The correlations between nitrogenous pollutants and groundwater level, irrigation quantity, drainage and return water were also investigated. The results indicated that the theoretical variogram model of Total Nitrogen (TN), Ammonium Nitrogen (AN) and Nitrate Nitrogen (NN) in different periods of irrigation (April, July and November) were presented well of the spherical, Gaussian and exponential forms. The residual sums of squares (RSS) of the theoretical variogram between the actual variogram of TN, AN, NN were in the range from 0.009 to 0.1238. The nitrogen in soil had a strong spatial relevancy except the ammonium nitrogen in November. The nitrogen content in soil was generally high in the northeast and low in the southwest in April and July. In the whole area, the total nitrogen and nitrate nitrogen in soil reached the highest content in April and the lowest in November, while the ammonium nitrogen in soil had the highest content in July and the lowest in November. The temporal and spatial variability of nitrogen in soil was strongly correlated with the groundwater level, irrigation quantity, drainage and return water.