Abstract
Difference of potassium (K) dynamics between grazing with sheep and cutting grasslands were investigated when three levels of K fertilizer NK : 0, LK : 7.5 HK : 27.5 kg/10a/yr, were applied to grasslands with mixed grass species. Outlines of results are as follows. 1. Dry matter (DM) yields in the cutting grassland were superior to those in the grazing grassland at the same K levels. The increases of DM yield by K application were shown in the cutting grassland but not clear in the grazing grassland 2. K concentrations of herbage in the grazing grassland were maintained at higher percentage than those in the cutting grassland at the same levels of K application. K yield of herbage in NK of grazing was higher than that of cutting, but in LK and HK, K yields of herbage in cutting was higher than those in grazing as the result of the increment of DM yield in LK and the luxuty absorption of K in HK by K application. 3. In the cutting grassland, more than K applied was absorbed by plants and removed from the grassland. On the other hand, in grazing grassland K absorbed by plants was less than K applied, and it was shown that most of K applied were accumulated in soil and residual herbage. 4. At the same K levels, exchangeable K in soil was higher in grazing than in cutting, in particular there was a remarkable difference between grazing and cutting. 5. There are two processes of K return, from urine and dead plant tissues in grazing grassland. At low K level, K return from urine will play an important role in K cycle and, in addition to this K return from herbage will be important under high K level.
