DRIS evaluation of the nutritional status of processing tomato

Diagnosis and Recommendation Integrated System (DRIS) norms were derived for processing tomato (Lycopersicon esculentum Mill.) from a 1993-94 survey of >100 fields in the Sacramento and San Joaquin Valleys of California. Relative foliar N, P, K, Ca, Mg, and S concentrations mere expressed in ratio form, with DRIS norms calculated as the means of fields with fruit yield greater than or equal to 90 Mg . ha(-1), Norms we re developed for three growth stages: first bloom, full bloom, and 10% of fruits ripe. Optimum foliar nutrient concentration ranges were calculated by regression analysis from DRIS nutrient indices of high-yield fields. These optimum ranges were in general agreement with existing empirically derived sufficiency ranges for N and P, higher for Ca, Mg, and S, and much lower for K, The relatively low foliar K levels observed were attributed primarily to the strongly determinate growth habit of currently used cultivars, In the fields sampled, yield-limiting nutrient deficiency appeared to be rare.