Nitrates in Celular Extract of Petiole in Greenhouse Tomato

The purpose of this study was to obtain information on N-NO₃ sufficiency ranges in sap of greenhouse tomato (Lycopersicon esculentum Mill “Beatrice”) growing under soil. The experiment was conducted during the winter-spring season on 2003-04. Crescents doses of nitrogen fertigation were applied at the crop during season, varying the nitrogen quantities since 250 until 1000kg ha^-1. Over the plant growth cycle, samples of the most recently mature leaves was taken, and the sap of central ribbing without foliage was analyzed with portable ionometers. The results shown high correlation between N-NO₃ concentrations and maximum relative yield (R² = 0.7858 - 0.9925). Sufficiency ranges in N-NO₃ concentration associated with 90-100% of relative yields were variables. Intervals found early season shown concentrations between 506 - 582 mg L^-1 of N-NO₃. Later in season shortest intervals in concentrations were found (201 - 210 mg L^-1 of N-NO₃). Results of this study illustrate the utility of use of quick nitrate test for monitoring nitrogen nutrition on greenhouse tomato.