Potato yield, petiole nitrogen, and soil nitrogen response to water and nitrogen

Detection of high NO3 concentrations in domestic weds has led to concern about excessive fertilizer N use in crop production. A potato (Solanum tuberosum L. cv. Russet Burbank) experiment was initiated to examine the effect of water and N on potato yield and quality, tuber N concentrations, petiole NO3 concentrations, and N distribution in the soil. The field trial consisted of a line-source irrigation system with six water rates (0.33, 0.66, 1.00, 1.10, 1.20, and 1.30 times crop evapotranspiration ETc) each having six planting-time N rates (0, 56, 112, 168, 224, and 448 kg ha(-1)) replicated four times with treatments applied to the same plots in two successive gears on a Pittville sandy loam (fine-loamy, mixed, mesic Typic Argixerolls). Yields were significantly increased with water, averaging 14.1 to 54.4 Mg ha(-1) in 1992 and 20.8 to 46.5 in 1993. Nitrogen rate significantly increased yield in 1993, averaging 28.7 to 41.1 Mg ha(-1), but not in 1992. Residual soil profile NO3-N (1040 mg kg(-1)) present at planting time in the first cropping season was utilized, denitrified, or leached from the top 150 cm of soil by above-normal winter rainfall before the beginning of the second season. At the end of the second season, low NO3-N concentrations were observed in soil profiles receiving 0, 112, and 224 kg N ha(-1), whereas a concentration of 1050 mg kg(-1) was found in the 0- to 60-cm depth of soil with the 448 kg N ha(-1) rate. High residual soil N in 1992 resulted in N use efficiency (NUE) for tubers of >200 g kg(-1); in the 1993 season, however, NUE was > 300 g kg(-1). Near-maximum yields were obtained with 1.10 to 1.20 ETc applied water and 0 to 56 kg N ha(-1) in 1992 and with 1.10 to 1.30 ETc applied water and 168 to 224 kg N ha(-1) in 1993.