Interaction of Fertilizer Phosphorus, Potassium, and Sulfur in a Corn-Soybean Rotation.

Fertilizer, which consists of more than one nutrient, is needed to maximize grain yield for corn and soybean production in the northern Corn Belt. Sulfur is increasingly being applied but potential interactions with other nutrients have not been fully established. It is common practice to apply most, if not all, of the needed fertilizer in a two-year corn-soybean rotation prior to planting corn. The objective of this research was to determine if sulfur applied to corn was cycling to the next years’ soybean crop and to determine if there was any interaction among, P, K, or S for corn or soybean. Four rates of K (0, 93, 186, and 279 kg K ha-1) were superimposed over a factorial combination of 0 or 28 kg S ha-1 and 0 or 59 kg P ha-1. Two year corn-soybean rotations were established at four locations in Minnesota. Soybean grain yield was never increased by fertilizer application even though plant tissue data indicated that P, K and S were carried over in the soil from the previous years’ application. Fertilizer S increased corn grain yield at two sites and P or K increased corn grain yield each at one site. Soil test P was high (> 20 mg kg-1 Bray-P1) and soils generally tested < 160 mg kg-1 by the ammonium acetate test. There was no interaction among any of the nutrients studied considering grain yield of either crop. It can be concluded from the data that 1) the response in corn grain yield from the addition of a nutrient (in this case P, K, or S) results in an additive effect on corn grain yield, and 2) when either P, K, or S is deficient no other nutrient can be applied to fully or partially recover a loss in grain yield.