Under most circumstances deep placement of P and K does not lead to increased yield over broadcast applications. (In SE coastal plains in sandy soils we may see leaching?). Soil sample and use recommendation of state testing facility. State soil testing labs.
For double-crop soybeans (planted immediately following wheat), both P and K could be applied before the wheat crop. If the wheat straw will be removed, K should be applied immediately after wheat harvest.
Phosphorus and Potassium are the most often applied nutrients for soybean. Typically, these can be applied prior to the previous crop such as corn in sufficient quantities to supply both crops. Soil test recommendations should be used to determine quantity of fertilizer required.
“For more information on this or other topics related to soybean production, contact your state extension specialist or your local extension educator/agent.”
The following is the link to the soybean extension specialists: state extension soybean specialist