Influence of rate and placement of phosphate fertilizer on growth and yield of hard red spring wheat in diverse tillage systems

Management of P is a major issue for crop producers who grow hard red spring wheat (Triticum aestrivum, L.) with conservation tillage. Compared to the use of the moldboard plow, tillage that leaves crop residue on the soil surface can cause changes in soil chemical, biological, and physical properties. These changes may affect management practices for fertilizer P. Two studies were conducted to evaluate the impact of rate and placement of fertilizer P on hard red spring wheat production in various tillage systems. In one study, P rates of 0, 5.5, 11.0, 16.5, and 22.0 kg ha^-1 were: (1) broadcast and incorporated, or (2) applied in a subsurface band prior to tillage, or placed with the seed at planting. The chisel plow was used for primary tillage in this study. In a separate study, P rates of 0, 20, 40, and 60 kg ha ^-1 were: (1) broadcast and incorporated, (2) applied in a subsurface band, or (3) applied with the seed at planting. These P rates and placements were used in a moldboard plow, chisel plow, and no-till planting system. There was a positive response to rate of fertilizer P used in both studies, with a higher rate needed for optimum yield when soil test levels for P were in the low rather than the medium range. Tillage system had an effect on yield with no-till < chisel plow < moldboard plow. There was no interaction between: (1) tillage system and rate of P applied, (2) tillage system and P placement, and (3) rate and placement of P fertilizer. The data collected from these studies lead to the conclusion that the recommended rate of fertilizer P should not be adjusted for either method of placement or tillage system.