Polymer Coated Urea Research Summary: Meeting Plant Requirements While Mitigating Environmental Impacts.

Fertilization is fundamental to agriculture. Nitrogen (N) is half of the global fertilizer input, but plant N recovery is inefficient due to system “leaks” causing air and water pollution. Inefficiency wastes resources and can reduce yields, quality, and profits. Optimal source, rate, timing, and placement increase Nitrogen-use efficiency (NUE). Polymer coated urea (PCU) is an N fertilizer that can reduce N loss to background levels. A summary of our laboratory, glasshouse, and field research trials comparing PCU to urea shows dramatic increases in NUE by decreasing N loss to air and water. Average ammonia volatilization and nitrous oxide emissions were lower for PCU by 300 and 120%, respectively. In studies with plants growing in fertilized soil, residual nitrate was 38% lower for PCU compared to uncoated urea. The N losses for PCU fertilized plants were nearly the same as the background levels in the controls. PCU resulted in significant improvements in crop yields and/or quality (average increase across our trials in potato, corn, and small grain yields is 9%) or at least equivalent to uncoated urea when managed properly. However, timing of application is critical—basing application on matching release curves to crop requirements. In addition, tissue analysis calibration may need adjustment. For example, PCU results in a reduction in potato petiole nitrate-N concentrations of ~2,000 mg kg^-1 without yield reduction. Widespread use of PCU is warranted in most crops if costs are reasonably close to uncoated urea—resulting in improved environmental quality and agronomic productivity.