Effect of Polyhalite and MOP As a K Source on the Yield and Nutrient Uptake of Maize in Sichuan, China.

Sichuan province in China is one of major provinces to produce maize with the planting area at 1371.1 (1000 ha). Potassium is an important nutrient to enhance maize yield. The type and rate of K fertilizer are two important factors to affect the growth of maize. Two different type of K sources (Polyhalite (POLY4) and KCl (MOP)) at different K rate (0, 75, 113, 150 and 225 kg K₂O ha^-1) with the same local recommendation rate of 300 kg N ha^-1 and 90 kg P₂O₅ ha^-1 from urea and mono ammonium phosphate were conducted for Maize in 2014 in Sichuan, China. The experiment was a randomised block design with each treatment plot at 20 m² in four replications.

The field trial showed that applying K of both POLY4 and MOP significantly increased maize kernel yield. Comparing the performance of the two type of K fertilizers, POLY4 significantly increased maize kernel yield, total biomass weight, plant height, cob height and number of green leaves over MOP. There was a positive correlation between rate of K fertilizer and maize kernel yield in both of two K sources (r = 0.844, p < 0.01 in MOP; r = 0.861, p < 0.01 in POLY4). Applying POLY4 and MOP also significantly enhanced total uptake of K in plant (grain +straw). There was a positive correlation between K rate and total uptake of K in plant (grain +straw) in in both of two types of K fertilizer (r = 0.685, p < 0.01 in MOP; r = 0.767, p < 0.01 in POLY4). Application of POLY4 significantly improved uptake of Ca, Mg in harvested straw of maize over MOP. And applying POLY4 significantly enhanced S content in straw and available S content in post harvested soil than applying MOP. The study demonstrated that applying POLY4 had better performance on the yield and nutrient uptake of maize than applying MOP. Beside K nutrient, the benefits from Ca, Mg and S in POLY 4 to improve maize production should be investigated deeply in future study.