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ISHS Acta Horticulturae 852: IV International Symposium on Ecologically Sound Fertilization Strategies for Field Vegetable Production

VALIDATION OF N NUTRITIONAL STATUS TOOLS FOR PROCESSING TOMATO

Authors:   M. Farneselli, P. Benincasa, F. Tei
Keywords:   N management, chlorophyll meter, petiole sap test, NNI
Abstract:
A field experiment was carried out in 2006 in Central Italy on processing tomato fertilized with 3 N rates (0, 100 and 300 kg N ha-1) applied by different fertigation-irrigation weekly frequencies. Growth analysis was performed by sampling plants every 2 weeks starting from 30 days after transplanting (DAT) for a total of 5 sampling dates (i.e., 30, 42, 57, 71 and 84 DAT). At each sampling date the dry weight of the different above-ground plant organs (stems, leaves and fruits) were determined. Reduced-N and nitrate-N concentrations were determined by lab analyses. At each sampling date the crop N nutritional status was also assessed by petiole sap testing and chlorophyll meter readings both taken from the apical leaflet of 10 youngest fully expanded leaves. The evaluation of the crop nutritional status (i.e., sub-optimal, optimal and luxury consumption) was determined by using for the sap test the sufficiency ranges proposed by UC Davis (Anonymous, 1997) and for the above-ground total-%N content the critical-N curve proposed by Tei et al. (2002). Results showed that the sap test is a reliable tool for assessing the N nutritional status in processing tomato for about 2/3 of the crop cycle (i.e., until the end of linear growth phase) that represents the crucial time for N fertilizer management in that vegetable crop. On the contrary, the SPAD chlorophyll meter in our experiment resulted less sensitive and less reliable.
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