Effectively increasing the yield and oil quality of sunflower by basal application of potassium fertilizers in Hetao irrigation area, Inner Mongolia

Objectives The research purpose is to compare the effect of potassium chloride and potassium sulfate application on yields and quality of sunflower, the research would provide the scientific support for cost effective potassium fertilizer application.

Methods Fertilization experiments were carried out in Hetao irrigated area, Wuyuan County, Inner Mongolia from 2014 to 2016. Potassium chloride and potassium sulfate were used as potassium fertilizers and applied in rate of K₂O 120 kg/hm². Three application treatments were set up as 100% basal application (100% B), 50% basal application + 50% dressing in squaring stage (50%B + 50%T) and 25% basal application + 50% dressing in squaring stage + 25% dressing at florescence (25%B + 50%T + 25%T), no potassium application was used as control. The sunflower yields and yield traits were investigated, the crude fat, protein and main fatty acid contents in sunflower seeds were analyzed, the K uptake and accumulation amount were determined, and the potassium fertilizer using efficiency were calculated.

Results Application of K₂SO₄ and KCl increased the yields of sunflower by 10.4% and 10.6%, respectively. The contents of crude fat and crude protein in sunflower seeds were increased by 2.17% and 1.95% using K₂SO₄, and 2.74% and 2.45% using KCl, respectively. There were no significant differences in the sunflower seed yield and quality between K₂SO₄ and KCl and among the three application modes. Potash application significantly increased the flower dish sizes, thousand-seeds weights, dish weights, there were no significant differences between the two potassium fertilizers and among the three application modes. The K absorption was increased significantly and the average use efficiency of potassium fertilizers was 47.7% in the 3 experimental years. The average agronomy efficiency of potassium fertilizers was 3.08 kg/kg. The application of potassium fertilizer increased the crude fat contents in sunflower seeds, and the ratio of unsaturated fatty acid by 2.20%. There was no significant difference between different potash varietis and different application modes.

Conclusions Application of potassium fertilizers is effective in increasing sunflower yields and oil quality in Hetao irrigation area. The effects are similar between the two potassium fertilizers, and the effects are the same among the application modes. Considering the potash price and the labor input, potassium chloride with once basal application is recommended in sunflower production in Hetao irrigation area.