太湖地区农田土壤中铵态氮和硝态氮的时空变异

对太湖地区农田土壤3种主要水稻土类型:白土、黄泥土和乌栅土在小麦和水稻生长期间土壤剖面中NH₄⁺-N和NO₃^--N含量的时空变异进行了研究.结果表明:NH₄⁺-N在1a中的2月份和9月含量较高;4月份和11月的含量较低.NH₄⁺-N在土壤剖面中的空间变异为土壤上层到土壤下层呈逐渐递减趋势,以表土层含量为最高,在40cm以下基本上趋于稳定.NO₃^--N的含量低于NH₄⁺-N,在1a中小麦生长季节(旱作)高于水稻生长季节(水作);NO₃^--N在土壤剖面中的空间变异为:旱作时的土壤表层到底层迅速下降;但在水稻生长季节土壤剖面中表层土壤的NO₃^--N含量低于底层的NO₃^--N的含量,出现明显的淋溶现象.在旱作期间NO₃^--N随NH₄⁺-N呈指数曲线变化,而在水稻生长期间没有这种关系.NH₄⁺-N和NO₃^--N含量与土壤有机质呈显著的直线线性正相关关系.但NH₄⁺-N和NO₃^--N仅在旱作时随土壤粘粒含量和土壤pH值的升高而呈对数曲线下降.

Time-Spatial Variability of Ammonium and Nitrate in Farmland Soil of Taihu Lake Region

Time-spatial variability of ammonium and nitrate in soil profiles of farmland soil(three main paddy soils: White soil,Huangni soil and Wushan soil) during wheat and rice growth was studied.The results were as follows: the ammonium content was high in February and September and low in April and November in 2004.The spatial variability of ammonium content in soil profiles was gradually decreased from surface soil layer to bottom soil layer.It was stable below 40 cm.The nitrate content was lower than the ammonium content.The nitrate content of the wheat growth season(dry cultivation) was higher than that of the rice growth season(water cultivation) in a year.The spatial variability of the nitrate content in soil profiles was quickly decreased from surface soil layer to bottom soil layer during dry cultivation.But during the rice growth season,the nitrate content of the surface soil layer in soil profiles was lower than that of bottom soil layer.It was leaching phenomenon of nitrate.The nitrate content was in a sharp positive relation with the ammonium and changed with exponential function during dry cultivation.But there was not this relationship during water cultivation.The ammonium and nitrate were significant relation with soil organic matter in straight line.But the ammonium and nitrate content decreased with the soil clay content and pH value increased and changed with logarithmic function.