Evaluation of a quick test to assess polymer-coated urea prill damage

Polymer-coated ureas (PCUs) can reduce N leaching in potato (Solanum tuberosum L.) production while maintaining yields. However, damage to the polymer coating during handling increases N release and potentially affects leaching and crop response. A 2-yr study was conducted to develop a quick test of PCU damage, compare its results with N release under field conditions, and determine damage effects on N uptake and yield in field experiments. A 24-h water immersion procedure was developed to measure N release differences from two sources of the PCU fertilizer Environmentally Smart Nitrogen (ESN) handled in different ways: ESN(C), dealer grade undamaged control, and ESN(A), damaged by air boom spreader application. Nitrogen release from ESN(A) was more rapid in both the 24-h test and during in situ soil incubation. Quick test results were positively correlated with N release during the first 7 d of field incubation (R² = 0.91, adjusted R² = 0.86). Differences in prill damage between ESN(C) and ESN(A) were greater in 2010 than 2011. Limited crop response differences occurred in 2011, but in 2010 petiole nitrate-N was more stable and higher late in the season for ESN(C) than ESN(A), and tuber, vine, and total N uptake were significantly greater for ESN(C). Tuber yield and size were not significantly affected by ESN damage. Based on these results, the quick test provides an accurate assessment of potential differences in N release during the growing season due to coating damage and can be used to evaluate leaching potential and possible need for fertigation.