上海郊区罗店旱地氮素的淋溶研究

渗漏流失是旱地农田氮素流失的主要途径之一，也是引起地下水污染的重要原因。上海市郊大面积旱地农田，雨季渗漏流失较为严重。基于氮素渗漏基本理论和当地农田管理习惯方式，为了研究不同施肥方式处理下氮素流失规律，对实验地进行3种不同方式处理：常规施肥、减量15％施肥、不施肥。结果表明，不同深度不同形态氮浓度随施肥时间递减，并且其递减幅度有所差异，递减幅度大致为30>50>70>120 cm。在垂直方向上，氮素在50 cm处有富集的趋势。硝态氮占总氮流失比例较大，各种不同处理方式下其所占比例均超过70％，是氮素流失的主要形态；铵态氮和亚硝态氮占总氮的比值很低，铵态氮主要分布在表层，并受施肥的影响较大。减量施肥能够减小土壤渗漏水氮素的浓度，提高肥料的利用率。

CHARACTERISTICS OF N-ELEMENT LEAKAGE IN THE DRY LAND IN LUODIAN IN SHANGHAI SUBURBS

Nitrogen leaching to the groundwater is one of the major nitrogen loss ways in dry land farming systems,and contributes to a large extent in groundwater pollution.In most of the dry land in Shanghai Suburbs,it is much more serious that nitrogen may leach to the groundwater in rain seasons.In this paper, effects of different fertilization methods on nitrogen transport were studied based on lysimetric experiment and orthdox tillage.Results of the experiment showed that the concentration of nitrogen decreased with fertilization time,and the decrease extent of nitrogen in different vertical depth differed,being in the order 30>50>70>120 cm.And nitrogen showed an accumulating tendency at 50 cm vertical depth.Nitrate was the main form of the leaehing nitrogen,with its proportion exceeding 70% under all treatment meth- ods;and the proportions of ammonium nitrogen and nitrite nitrogen were very low.Reducing chemical fer- tilizer can improve the utilization of fertilizer and decrease the concentration of nitrogen in the leakage water.