渭北旱塬梯田土壤氮素特征及影响因素分析

Analysis on characteristics and influencing factors of soil nitrogen for terrace in the Weibei dryland

测定不同利用年限梯田土样的有机质、全氮、速效氮、矿质氮(NH4+-N+NO3--N)以及其它理化指标,利用统计分析法系统分析渭北旱塬梯田土壤的氮素特征、剖面变异性及影响因素。结果表明,土壤氮素含量缺乏(全氮除外)且分布不均,特别是矿质氮很贫乏;各形态氮素表层含量最高,沿剖面向下降低,表层与下层含量差异显著;施肥可明显提高氮素含量;CEC、粘粒、全磷和速效磷含量对有机质、全氮和速效氮含量正向影响较大;CaCO3和粉粒含量对土壤氮素具有"稀释效应";坡位、坡向和梯田类型对土壤氮素也有一定的影响;随利用年限的增加,有机质、全氮和速效氮含量先增后降,开始衰退的年限在19 a以上。

Testing the content of organic matter（OM）,total nitrogen（TN）,available nitrogen（AN）,mineral nitrogen（NH4^＋-N＋NO3^—N） and other physical-chemical properties under different use years of terrace.Using statistical analytical method,the characteristic,variability in profile of soil nitrogen and its influencing factors for terrace were studied systematically in the Weibei dryland.The results showed that distributions of various soil nitrogen were uneven and their contents were poor except for TN,especially,the content of mineral nitrogen（MN） was very poor.The contents of various soil nitrogen in topsoil were highest and their contents decreased from upper to lower in vertical profile and their significant differences were found between topsoil and lower layers.Fertilization increased obviously the content of various soil nitrogen.OM,TN and AN were influenced obviously and positively by the contents of CEC,clay particle,total phosphorus（TP） and available phosphorus（AP）.The contents of CaCO3 and silt particle made ＂dilution effect＂ of soil nitrogen.All soil nitrogen was effected to some extent by aspect and position of the slope and type of terrace.The content of OM,TN and AN increased incipiently and decreased subsequently with the increasing of terrace use years,the degraded critical year of them was 19 years at least in study area.