Research on characteristics of soil potassium of artificial farmland in loess hilly region

Through analyzing soil samples and using statistical analytical method,characteristics on contents,correlations and vertical and temporal distributions of soil potassium for artificial farmland——dam land and terrace in loess hilly region were studied systematically.The results showed imbalances of soil potassium were serious in dam land and terrace.Average content of readily available potassium(RAK) of topsoil belonged to medium level in dam land and lacking in terrace.Average content of total potassium(TK) of topsoil belonged to level in dam land and medium level in terrace.Average content of slowly available potassium(SAK) was respectively 7.58 times and 11.06 times of that in RAK in dam land and terrace,but its transition ratio was low.Average content of mineral potassium(MK) took up respectively 95.71%(dam land) and 95.16% (terrace) of that in TK and it was difficult to be utilized by crop.The interrelations between various soil potassium were very significant positive correction,and they were influenced by organic matter,CEC,pH value and particle size distribution of soil.Very significant differences were found for RAK in top layer and lower layer of soil profile and for SAK in dam land and terrace.As a whole,soil potassium of loess parent material was even.The content of RAK for dam land increased from upper to lower in vertical profile and was wholly higher than that of terrace.The content of SAK in dam land was lower than that of terrace because of depletion for maize.In the process of temporal change,available potassium,RAK and SAK increased firstly and decreased subsequently,and the critical time was about 40 years in dam land and 30 years in terrace.