Potassium Sources for Soybeans

This project was conducted to determine whether chloride or magnesium applied with potassium (K) fertilizers influence soybean yield and quality, and to determine whether Ontario soybean cultivars differ in response to sources of K. The experiment was conducted over four years beginning in 1999. In 2000 and 2002, soybeans were planted following soybeans, with treatments applied to the same plots as the previous year. In each case, soybeans responded more strongly to applied K in the second year than in the first year. In 2000, all sources of K increased yield by about 12%.

In 2001 and 2002, cultivar by K source interactions occurred, with some varieties responding more positively than others to K, and some varieties showing sensitivity to muriate of potash (KCl). In 2000 and 2001, K also increased seed size and sugar, and slightly decreased protein. Potassium decreased disease in 1999 and 2001, but had little effect in 2000. Results indicate that soybeans following soybeans need substantially more K than following corn. ON-18