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The Pre-sidedress Soil Nitrate Test (PSNT) has shown promise in the humid eastern United States as an effective tool for predicting nitrogen (N) fertilizer needs of corn (Zea mays L.). The purpose of this three-year study was to evaluate the PSNT under irrigated conditions of the semi-arid western United States. The specific objectives were to determine the critical nitrate-nitrogen (NO3-N) concentration range at the 6-leaf (V6) growth stage of corn and the best soil sampling position and depth. Experiments were conducted in farmers' corn fields selected for low residual soil NO3-N levels. Four pre-plant main plot N rates (0, 47, 90, and 134 kg N/ha) and two subplot sidedress N rates (0 and 67 kg N/ha) were used. Soil was sampled at the V6 growth stage (PSNT) for NO3-N analysis. Soil samples were collected from 0-30 and 0-60 cm depths from three positions relative to the corn plants: in the row, on the shoulder of the row, and in the bottom of the furrow. There was a good correlation between PSNT soil NO3-N concentrations and percent relative yield (r(2) = 0.58). Composite soil samples from the furow and shoulder positions resulted in a higher correlation between PSNT NO3-N and percent (%) relative yield. The results showed a critical PSNT NO3-N concentration range of 13-15 mg/kg for 0-30 cm sampling depth. This critical PSNT concentration range is substantially lower than the 21 mg/kg suggested in the humid region of the United States. The reason for the difference may be due to the higher concentrations of subsoil (60-120 cm depth) NO3-N found in many soils under irrigated conditions in the semi-arid west. Our soils are not tile drained or subject to leaching during the winter or spring.