Comparison of ESN and Urea on Potato Petiole Nitrate and Yield in Southeast Idaho.

Nitrogen (N) is a costly input commonly lost to the environment through leaching, volatilization, and denitrification. Previous studies show a polymer coated urea known as Environmentally Smart N (ESN) is effective in potato (Solanum tuberosum L.) production. The purpose of this research was to determine if combinations of ESN with in-season fertilization of uncoated urea result in tuber quality and yield increases and to examine the impact on in-season petiole tissue nitrate-N concentrations. Russet Burbank potato was grown at the Brigham Young University-Idaho Hillside Farm in Rexburg, ID. An untreated control was compared to ten N fertilized treatments with all combinations of three at cultivation (urea applied at 50% N and ESN applied at 50% or 75%) and three in-season (0, 50, or 100% applied as urea) fertilization treatments. US No. 1 yields increased with the first increment of N fertilization. The only fertilized treatments different from one another had 50% N applied at cultivation, but no additional in-season N fertilizer applied. In this case, ESN performed significantly better than urea at the same rate due to a greater number of the largest size tubers. Surprisingly, increasing the N rate did not result in continued increases of yield or tuber quality—regardless of fertilizer source or timing. In general, the petiole nitrate values of ESN vs. urea at 50% was 2,484 ppm greater nitrate for urea when averaged over the course of the season, with a similar trend when 50% of the in-season N was applied but not when 100% was applied. Although results may have been different under a more typical N response, these data show: 1) ESN provides an advantage over urea at the appropriate N rate and 2) traditional petiole nitrate values based on calibration with urea and other traditional N sources may not be valid.