Alternatives for P and K Management:

Adequate amounts of soil phosphorus (P) and potassium (K) are needed to support sustained corn and soybean production. These requirements have been recognized for a long time, and soil testing is a useful tool to estimate P and K fertilization needs. Obviously, fertilizer applications to low-testing soils increase grain yield and result in economic benefits for crop producers. Continued P and K fertilizer applications increase soil-test P and K values over time, and this is considered a desirable consequence of fertilization when soil test are initially low. However, long-term use of fertilization has increased soil-test P and K levels of many Iowa soils to levels usually considered above optimum for corn or soybean. With current low crop prices, producers are looking at ways of cutting back in inputs. The presentation will review aspects of P and K management related to use of soil testing to decide fertilizer rates and will summarize recent information on alternative placement methods for P and K, which include starter and dep band preplant applications. With this information, producers can make decisions about most appropriate fertilization practices for their conditions.