Impact of Maleic-Itaconic Copolymer On Phosphorus Nutrition of Soybean.

Phosphorus (P) nutrition management remains challenging. Settings, defined either by P deficiency or P excess, have been identified. Improved P use efficiency is important in both contexts as soluble P amendment rates might be curtailed by economic or environmental concerns. Purveyors of maleic-itaconic copolymer impregnation of granular P fertilizers promise improved P use efficiency via reductions in soil P fixation. The objective of this study was to determine the impact of diammonium phosphate (DAP) impregnation with maleic-itaconic copolymer on soybean P nutrition. Soybean was grown at soil test P levels ranging from 4 to 8 ppm (Mehlich III), to insuring that improved P availability was discernable. Four treatments were imposed at each soil test P level; as diammonium phosphate (DAP) at rates of 0, 11 and 22 kg P/ha, and as copolymer impregnated DAP at 11 kg P/ha; in four replicates of randomized complete blocks. Leaves were taken at growth stage R1, grain was sampled at harvest, and P concentrations determined in both tissues. Leaf and grain tissue P concentrations, and yield, responded strongly and positively to greater P nutrition at all soil test levels, though drought after R1 reduced yield. The maleic-itaconic copolymer did not improve P availability.