Corn harvest ran late, but I still want to apply phosphorus and potassium for soybeans before spring, if possible. When is it OK to apply? Are there rules in Indiana about applying fertilizer on frozen soils? Are there fields to avoid?

The panel of Indiana certified crop advisers answering this question includes Steve Gauck, Beck’s sales agronomist, Greenburg; Andy Like, Syngenta, Vincennes; and Jeff Nagel, Ceres Solutions agronomist, Lafayette.

Gauck: There is still plenty of time to apply fertilizer before soybeans. Many agronomists now recommend spring-applied nutrients. The Office of Indiana State Chemist regulates when and how nutrients can be applied. Its website has application restrictions that say you can’t apply to saturated ground, but you can apply inorganic fertilizer to frozen ground. The biggest challenge to applying on frozen ground is the concern of a heavy rain shortly after application that could move nutrients.

In an ideal world, we would wait and apply fertilizer right before planting, when soils are dry and warming. If that isn’t possible, avoid applying nutrients on frozen ground in fields that have lots of slope where nutrients could move from the field.

Like: Assuming the P and K you want to apply is inorganic, such as DAP and potash, you can apply anytime you want if it isn’t applied on standing water or on saturated ground. Application on frozen ground is permitted, although it may not be a best practice. I would avoid fields with a high potential for P and K to run off and enter a stream or creek.

If your P and K is applied as manure, different rules apply. Those can be found at oisc.purdue.edu.

Nagel: In short, apply anytime ground conditions are fit and runoff potential is minimal. Essentially, for inorganic fertilizers such as 11-52-0 (MAP), 18-46-0 (DAP) or 0-0-60 (potash), you can apply anytime ground conditions are suitable for application equipment. Applications can be made to frozen ground, but potential runoff could occur if made prior to a significant rainfall event. The following are a few guidelines for dry fertilizer applications: