Abstract: Using the 13-year fixed site field trials located at selected locations in three provinces of northeast China, Liaoning, Jilin and Heilongjiang, effect of K fertilizer use on maize yield and soil K status in the plough layer was studied. Results showed that effect of K application on maize yield was quite different between the three fixed sites. In the field trial in Heilongjiang, significant maize yield response to K was found starting in the first year; in Jilin, the significant yield response to K was found starting in year 3; while in Heilongjiang, the maize yield response to K was not very stable from 1993 to 2005. The ranges of yield response to K fertilizer application in the field trials in Liaoning, Jilin and Heilongjiang were 9.9%-10.3%, 12.6%-13.6% and 17.5%-21.7%, respectively. In all three sites, K balance in soil-crop system was negative in the treatment with K2O application rate at 112.5kg/hm2, and remarkable K accumulation in soil was found when K2O application rate was 225.0 kg/hm2. Application of K fertilizer significantly increased soil available K content, and the increase in slowly available K in soil was not significant. Considering maize yield and income and soil K status, suitable, quantity of K fertilizer (K2O) was 112.5 kg/hm2 under present experimental conditions.

Key words: Long-term application of K fertilizer, Spring maize yield, Soil K