Abstract: Taking rice-rape rotation system as research object, the effects of potassium （K） application rates on rice-rape rotation system crop yield, K accumulation and use efficiency of rice and ripe were studied by fields experiments with K₂O rates of 0, 120 and 240 kg/hm². In which, the K₂O rate of 120 kg/hm² is recommended amount of potassium fertilizer for local soil test formulations. The results showed that crop yield of the rice-rape rotation system was increased at the first and then gradually decreased with the increment of the K application rates,and reached maxima under the K fertilizer application rate of K₂O 120 kg/hm². The K fertilizer utilization efficiency of rice and rape were decreased significantly with the increment of the K application rates. In conclusion, under this field experiment conditions, the optimal K fertilizer application amount is K₂O 120 kg/hm² in Wuxue city, Hubei province.

Key words: rice-rape rotation system, yield, K application rate, K use efficiency