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.