The influence on the dynamic change of the brown soil K when soybean and maize are cropped by rotation is researched through
25 years long-term localization experiment. The result indicates: in each processing the change
tendency of content of available
potassium and slow release potassium for the soybean year all disappears to be larger than that for the maize year(1992>1993year,2002>2003year),the content of mineral potassium for the soybean year is less than that for the maize year. When CK,N1 and N1P three disposal are not fertilized with K chronically in soil various shapes K all assumes year by year drops, the drop scope of available and slow release potassium for the maize year is quicker than that for the soybean year, the mineral potassium for the maize year is slower than that for the soybean year. For a long-term executing the K in each processing the content of available potassium assumes rise tendency year by year; the content of slow release potassium assumes drop tendency year by year from 1992; the content of mineral potassium assumes rise tendency for maize year and drop tendency for soybean year. Four years related statistical analysis indicates correlation notability is invariable along with between the planting fixed number of years increase between soil available and slow release potassium.