Evaluation of an Organic Copolymer Fertilizer Additive on Phosphorus Starter Fertilizer Response by Corn

Fertilizer additive products have recently been developed with the intention of reducing phosphate fixation and improving phosphorus plant availability. We conducted two experiments at multiple North Carolina locations from 2007-2009 to evaluate the effects of an organic copolymer phosphorus fertilizer additive, AVAIL Phosphorus Fertilizer Enhancer (Specialty Fertilizer Products, Leawood, KS), on corn (Zea maize L.) nutrient uptake, growth, and yield. Treatments included a combination of diammonium phosphate (DAP, [(NH₄)₄HPO₄]) P fertilizer rates with and without AVAIL. Grain yields did not differ across fertilizer treatments or across low, medium, or very high initial soil test phosphorus. Grain P concentration differed among treatments in only 2 of 16 site-years, where the N-only treatment had less tissue P than the treatments including P with or without AVAIL. Also, N-only plots occasionally had shorter plants compared with DAP and DAP + AVAIL. Treating DAP with AVAIL did not consistently affect corn plant growth parameters in the Piedmont and Mountain Regions of North Carolina, and using treated DAP did not offer a consistent agronomic benefit over DAP- or N-only fertilization.