Abstract: In order to discuss the suitable amount of potassium fertilizer for soybean[Glycine max （L.） Merr.], two-year field trials were conducted in 2017 and 2018 in Linying county, Henan province. Four potassium fertilizer gradients （K₂O application amount of 0, 60, 120, 180 kg/hm²） were set up to analyze the effect of K₂O amount on soybean dry matter, nutrient accumulation, yield, fertilizer utilization rate and economic benefits. The results showed that the dry matter and nutrient accumulation of soybeans increased continuously with the advance of the growth period, and the dry matter accumulation rate was fast from the flowering and pod-forming stage to the grain-filling stage. In 2017, the dry matter weight of mature soybeans increased first and then decreased with the increase of potassium application amount, and the potassium accumulation continued to increase with the increase of potassium application. The dry matter and potassium accumulation of mature period in 2018 both increased with the amount of potassium increases. In 2017, the yield of soybean had no significant difference among all treatments. In 2018, compared with control that without potassium application, the yield of different potassium application treatments increased by 34.3% to 52.7%, and this difference all reached significant level. The yield and increased economic benefit of applying K₂O 120 kg/hm² was the highest. So, the recommended amount of potash fertilizer is about 120 kg/hm² K₂O in the middle Henan province.

Key words: soybean [Glycine max （L.） Merr.], potash, yield, dry matter, nutrients