渭北旱塬梯田土壤钾素状况及影响因素分析

对渭北旱塬梯田土壤钾素特征、剖面变异性及影响因素的系统研究表明,表层各形态钾素中有效性钾和速效钾的空间变异性最大,钾素分布并不平衡;整体来看,因富钾矿物的作用导致钾储量(矿物钾和全钾)充盈,但约95%对植物长期无效;有效钾素(有效性钾和速效钾)的供应及潜在给源(缓效钾)都较富足。在80 cm剖面内,各形态钾素的变异性既反映出它们之间可相互转化,也揭示出梯田植物受钾素影响的范围在60 cm以内。有机质、CEC和粘粒对有效钾素影响较大;CaCO3和pH值对各形态钾素呈负效影响,特别是CaCO3对缓效钾的"稀释效应"最为明显;坡位、坡向和梯田类型对土壤钾素都有一定程度的影响;研究区梯田耕种至少17年以上钾素开始衰退,但降幅较小。

Analysis on Status of Soil Potassium and Its Influencing Factors for Terrace in Weibei Dryland

The characteristic,variability in 80 cm profile of soil potassium and its influencing factors in terrace were studied systematically in the Weibei dryland.The results showed that the spatial variability of available potassium(AK) and readily available potassium(RAK) were most large among various soil potassium of topsoil,and distributions of various soil potassium were uneven.As a whole,the function of rich potassium mineral caused plentiful reserves of mineral potassium(MK) and total potassium(TK),but for plants in terrace,about 95% of them was useless for long,and the supplies and potential sources(slowly available potassium,SAK) of AK and RAK were richer.In 80 cm profile of terrace,the variability of various soil potassium reflected that they could transform one another and revealed that influencing range of soil potassium to plants in terrace was within 60 cm.AK and RAK were influenced obviously by OM,CEC and clay particle. Various soil potassium was effected negatively by CaCO3 and pH value,especially,"dilution effect" to SAK made by CaCO3 was most obvious.All soil potassium was influenced to some extent by aspect and position of the slope and type of terrace.The degradation of soil potassium began in after terrace had been cultivated at least 17 years in study area,but their degraded speed was slow.