Polymer Coated Urea Impact on Petiole Nitrate-N Concentrations.

Polymer Coated Urea Impact on Petiole Nitrate-N Concentrations

Potato (Solanum tuberosum L.) is especially sensitive to deficiencies and excesses of nitrogen supply. Polymer Coated Urea (PCU) can be an effective nitrogen source for potato through increased yields and tuber quality and decreased environmental impacts. However, a majority of potato growers utilize weekly petiole tissue analysis to guide their efforts to provide a steady supply of nitrogen to their crop and PCU has been shown to give differing values, as compared to traditional nitrogen sources, for this important analytical tool. Eight years of field trials and grower strip trials were conducted in Southern Idaho. A PCU, ESN (Environmentally Smart Nitrogen, 44-0-0, Agrium) was compared to uncoated urea (46-0-0) at identical rates and untreated controls. An average across 124 site years of data reveals that the petiole nitrate-N concentration was 2050 mg kg^-1 less for the PCU than urea regardless of stage of season or potato variety. Despite the lower nitrate concentration, yields were typically higher for PCU than urea. We hypothesize that the steady release of nitrogen from the fertilizer prill enables the plant to take up a higher percentage of this nutrient in the ammonium-N form and, thus, is not measured as nitrate. Studies are underway to evaluate this theory.