Managing Phosphorus Inputs into Soybeans – When Should Application Occur?
When it comes to fertilizing crops with phosphorus in the Midwest, the typical perspective is that the timing is not overly critical. Phosphorus applications can occur in the fall or the spring, and application can occur every year or every other year. Historically, phosphorus applications occur in the fall (or the spring) ahead of corn planting at a rate that usually covers both crops in the corn-soybean rotation. The goal is to ensure an adequate supply of phosphorus to maintain soil test values at a level that is considered adequate.
Some recent research out of the University of Minnesota is challenging that notion on soybeans grown on high pH soils (>8.0). Researchers have found that high pH soils (specifically soils below the medium range of soil test phosphorus) can be responsive to fertilizer applied specifically for soybeans in the soybean year rather than an application for the rotation (where phosphorus is supplied for both crops prior to corn, but not the soybeans). Soybean yields were increased by 20 percent when phosphorus was applied prior to soybean planting.
If you would like more info, here is the article from University of Minnesota Extension.
