Methods of plant analysis to evaluate nitrogen status in sugarbeet
1997
Mambelli, S. | Dal Rio, M.P. | Amaducci, M.T. | Venturi, G. (Bologna Univ. (Italy). Dept. of Agronomy)
Accurate prediction of the minimum amount of nitrogen fertilizer required for optimum sugarbeet production and quality benefits the growers, the sugar factory and the environment. The use of plant tissue tests as a tool for nutrient deficiency diagnosis and for providing information for adjusting fertilization programs is increasing. A comparison of tissue testing techniques was conducted on sugarbeet crops fertilized with nitrogen input ranging from 0 to 180 kg per ha. Crop nitrogen status was assessed at 4-6, 8-10 and 10-12 true leaves stages (16, 31 and 39 days after emergence). The following indicators were considered: leaf nitrogen content (Kjeldhal method), chlorophyll content (SPAD-Minolta), petiole (Nitrat Schnelltest and ione-selective method) and crown nitrate levels (Nitrat Schnelltest). Leaf N values were positively related to petiole nitrate concentrations. A similar relationship between leaf nitrogen content and chlorophyll meter readings improved after the first sampling date. Quick test of petiole nitrate was found to be well correlated with the analytical determination. Crown nitrate concentration was an indicator not sensitive enough to show differences among the treatments and was poorly correlated with the leaf nitrogen content. Nitrate determinations were characterized by high variability, in spite of the method and plant organ used. Critical levels for separating deficient and adequate nitrogen crop status were identified. Further studies under different conditions are needed to confirm these preliminary results.
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