Soil- and plant-based indices in potato production in response to polymer-coated urea.

Cambouris, A.N., St. Luce, M., Ziadi, N., and Zebarth, B.J. (2014). "Soil- and plant-based indices in potato production in response to polymer-coated urea.", Agronomy Journal, 106(6), pp. 2125-2136. doi : 10.2134/agronj14.0041  Access to full text

Abstract

Polymer-coated urea (PCU) is used in potato (Solanum tuberosum L.) production to maintain or improve tuber yield while minimizing N losses, but the mode of N release is different from conventional soluble N sources. Hence, it is not known how soil- and plant-based indices of N availability would perform in response to PCU application. A 3-yr study was conducted on a sandy-loam soil in Quebec, Canada, to examine the effect of PCU application rate (0, 60, 120, 200, and 280 kg N ha1) on petiole NO3–N concentrations, chlorophyll meter readings (SPAD readings), soil mineral N content, and total tuber yield. Nitrate availability throughout the growing season was monitored by measuring NO3 adsorbed by anion exchange membranes (NO3{SUB}A{/SUB}{SUB}E{/SUB}{SUB}M{/SUB}). The NO3{SUB}A{/SUB}{SUB}E{/SUB}{SUB}M{/SUB} values, petiole NO3–N concentrations, SPAD readings, soil mineral N content, and total tuber yield increased with PCU application rate. The NO3{SUB}A{/SUB}{SUB}E{/SUB}{SUB}M{/SUB} values fluctuated during the growing season due to plant N uptake and variations in soil moisture content. Using all the PCU rates across years, we found that relative yield was better related to petiole NO3–N concentrations measured at 45 to 50 d after planting (DAP) (R2 = 0.95) and to cumulative NO3{SUB}A{/SUB}{SUB}E{/SUB}{SUB}M{/SUB} values measured up to 49 DAP (R2 = 0.91) than soil mineral N (R2 = 0.67), soil NO3–N (R2 = 0.65), and SPAD readings (R2 = 0.53) measured at 45 to 50 DAP, respectively. This study showed that soil- and plant-based indices of N availability can be used as early indicators of yield response in potato fertilized with PCU.

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