New research shows phosphate fertilizer may increase soybean protein

Soybean yields increase about 15% when you apply recommended rates of phosphorus fertilizer when soil test levels are low or very low. In addition, new research shows that the added phosphate may increase the protein percentage by about 1%, says George Rehm, U of M extension soil scientist, although he cautions that more research is needed on the effect.

A yield response can be expected when phosphorus as measured by the Bray procedure is 10 parts per million (ppm) or less, Rehm says. If phosphorus is extracted by the Olsen test, expect a positive response to phosphate fertilization if the value is 8 ppm or less. With a yield potential of 40 to 50 bushels per acre and a low soil test for phosphorus, the value of the added yield can be in the range of $42 to $56 per acre with $7 soybeans. The fertilizer cost for the increase is about $12.50 per acre.