EFFECT OF LONG-TERM POTASSIUM FERTILIZER LEVELS ON THE YIELD OF RAINFED CORN IN NORTHEAST CHINA

The excessive application of potassium (K) fertilizer over the last 30 years has resulted in considerable resource waste and environmental risk. In order to economize and protect the environment, China launched a soil testing and fertilizer recommendation project from 2005 to 2015. A total of 1370 on-farm experiments were conducted concerning maize fields in Jilin Province Northeast China, also called the golden maize (Zea mays L.) belt, over the past ten years to evaluate the effects of the implemented project and to provide farmers with an improved fertilizer recommendation system. The results showed that the average yield of maize with K0 treatment was 9000 kg ha(-1). Its maximum yield (Max.yield) and increased yield (IY k) after application of K fertilizer averaged at 10200 kg ha(-1) and 1100 kg ha(-1), respectively. Significant variability was evident in KO yield and Max.yield over the years. Maize hybrids and different soil types had significant differences in IY yield. Meanwhile, IY k can either increase or decrease depending on K0 yield, which suggest that a suitable K fertilizer can improve the yield, whereas excessive fertilizing would have no obvious effect on the yield. In addition, the yield was found to be affected by environment, maize hybrids, soil types, and K fertilizer rate.