TY - JOUR T1 - Fate of <sup>15</sup>N Fertilizer Applied to Trickle-irrigated Grapevines JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 191 LP - 198 DO - 10.5344/ajev.1998.49.2.191 VL - 49 IS - 2 AU - S. Hajrasuliha AU - D. E. Rolston AU - D. T. Louie Y1 - 1998/01/01 UR - http://www.ajevonline.org/content/49/2/191.abstract N2 - Information on fate of nitrogen applied to vines is needed to improve fertilizer management. Nitrogen-15 enriched ammonium and nitrate fertilizers were applied in the spring through a trickle irrigation system to six Thompson Seedless vines of a vineyard on the West Side of the San Joaquin Valley of California. At fruit harvest, all above-ground plant parts were removed and analyzed for 15N. Soil around each vine was also sampled and analyzed for 15N in the inorganic and organic N fractions. Spatial patterns of fertilizer N for soil inorganic and organic N were analyzed using a median polish technique which indicated large variability with respect to direction, distance, and depth. There was a tendency for the fertilizer N from NH4 to be located directly beneath emitters than from the NO3. Nitrogen from the NH4 application penetrated to only the 150-cm depth, whereas some N from the NO3 application reached 210 to 240 cm. Most of the organic fertilizer N for both NO3 and NH4 applications was in the top 60 cm of soil where the vine roots were likely of greatest density. Overall recovery of fertilizer N was also quite variable, probably due to variability in soil physical properties and uneven surface application of water and fertilizer due to local surface ponding. Although not statistically significant, uptake of fertilizer N by above-ground plant components was slightly higher for the NH4 application (24.2% of applied N) than the NO3 application (21.5%). Soil organic N had significantly (95% level) higher N from NH4 (19% of applied N) than from NO3 (13%). This probably occurred due to longer residence time of N from NH4 within the top 60 cm, where the bulk of roots and microbial activity existed, than for NO3. Overall, about 67% to 79% of the fertilizer N applied in spring remained in the soil at harvest, and the vines took up the rest. There was no indication of significant N leaching below 2.4 m or denitrification of fertilizer N for the trickle-irrigated vines during the growing season. ER -