Response of Wheat to Different Application Rate of Polyhalite in Jiangsu, China.

Jiangsu province in China is one of major provinces to produce wheat with the planting area at 2132.56 (1000 ha). Applying K fertilizer is one of important strategies to increase wheat yield. The adequate rate of K applied is efficient to maintain wheat yield with economic use of K source. Two field experiments with applying different rate of polyhalite (POLY4) (0, 45, 90 and 130 kg K₂O ha^-1) at the same rate of 140 kg N ha^-1 and 200 kg P₂O₅ ha^-1 from urea and monoammonium phosphate were conducted in 2014 at Buzhi and Wanguanj, Jiangsu respectively. The experiment was a randomised block design with each treatment plot at 30 m² in four replications.

The two field trials demonstrated that applying POLY4 significantly increased wheat yield in both of Buzhi and Wanguanj. But response of wheat yield to rate of POLY4 varied with the site of field trial. The highest yield of wheat was at the rate of 130 kg K₂O ha^-1 in Wanguanj and at the rate of 45 kg K₂O ha^-1 in Buzhi. There was a positive correlation between rate of POLY4 and wheat yield in the two sites (r = 0.617, p < 0.05 in Wanguanji; r = 0.207 in Buzhi). Applying POLY4 also significantly enhanced total uptake of K, Ca and S in plant (grain +straw) in Buzhi and total uptake of Mg in plant in Wanguanji. There was a positive correlation between rate of POLY4 and soil available K content in post harvested soil (r = 0.307 in Wanguanji; r =0.654, P < 0.05 in Buzhi). The study demonstrated that applying POLY4 can enhance uptake of nutrient in plant, soil available K content and improve wheat yield in the field condition. Further research is needed to investigate the response of wheat to POLY4 in variable soil type and find the mechanism relationship between optimum recommendation POLY4 rate for wheat production and soil characteristics.