太湖地区水稻土的硝态氮穿透曲线及影响因素

用模拟土柱的方法对太湖地区三种主要水稻土的硝态氮垂直运移穿透曲线和影响因素进行了研究。结果表明:对同一种土壤而言,土层由上往下土层的出流速度减慢,硝态氮的穿透过程推迟。对这三种土壤而言,乌栅土的各土层的平均流量最小,穿透时间最长。在水分饱和和充分淋洗的条件下,硝态氮能完全穿透土柱,硝态氮的垂直运移过程主要受土壤粘粒含量的影响,随着粘粒含量的增加出流速度减小,硝态氮的穿透开始时间推迟,硝态氮的穿透曲线峰值变低、峰面分布变宽,穿透曲线变化平缓。所有的穿透曲线都显得不对称,粘粒含量越高的土壤越有明显的拖尾现象。土壤容重和有机质含量对硝态氮的垂直运移有很大的影响;容重越小、有机质含量越高,出流的流量就越大,穿透开始的时间也就越提前;有机质与穿透总时间有极显著的相关性;有机质含量越高,穿透总时间就越短。

Breakthrough Curves of Nitrate -N in the Main Paddy Soils in Tai- Lake Region and Influencing Factors

The breakthrough curves of vertical transport of nitrate-N and its influencing factors in the main paddy soils(Bai soil,Yellow soil and Wushan soil) in Tai-Lake region were studied by simulated soil columns.The results showed that the flow velocity of nitrate-N was lowered and the breakthrough process of nitrate-N was prolonged from the surface layer to the bottom one in a soil depth profile.Among the three soils,the average flow velocity of Wushan soil was the smallest and the breakthrough process was the longest.When the soil was saturated and filtered adequately,nitrate-N could penetrate the soil column thoroughly.The transport of nitrate-N was affected by clay content and as the clay content increased,the outflow of nitrate retarded,the starting time of breakthrough of nitrate-N deferred,the peak value of break through curve decreased,and the area became wide and the curve became gentle.All of the curves were dissymmetric.The trail of curve was delayed more obviously when the clay content was higher.The vertical transport of nitrate was also affected by soil bulk density and organic matter content.When soil bulk density was low and organic matter content was high,the out flow became fast and the starting time went forward.The higher organic matter content,the faster breakthrough process was.