Many Iowa fields require phosphorus (P) and potassium (K) fertilization for optimum soybean production. Suggested application rates, when required and based on soil testing, are fairly large amounts. Fertilizer application methods and equipment commonly used to supply these nutrients are adapted to apply these large fertilizer rates to the soil before planting. Foliar fertilization, on the other hand, can be used to apply only small amounts of nitrogen (N), P and K, and also to apply sulfur (S) and micronutrients.