-In the present study, a 2-year N rate response experiment was conducted in different fields to monitor NO 3 -N soil profiles, N accumulation by the crop and final crop performance, in order to assess if soil NO 3 -N at pre-sidedressing (Pre-Sidedress Soil Nitrate Test, PSNT) is a reliable indicator for soil N availability for corn in the irrigated area served by canal d'Urgell (Lleida, Spain), and if the test can be used to separate responsive fields from non-responsive fields to sidedress N fertilizer applications. Preliminary soil N availability (N sidedress fertilizer rate + PSNT) critical levels to identify fields that need supplementary N fertilizer applications were established at ca. 300 and 210 kg NO 3 -N·ha nitrate du sol / PSNT / azote / dose de fertilisant / maïs