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.