EFFECTS OF A PROTEIN HYDROLYSATE APPLIED BY FERTIGATION ON THE EFFECTIVENESS OF CALCIUM AS A CORRECTOR OF BLOSSOM-END ROT IN TOMATO CULTIVATED UNDER SALINE CONDITIONS

The effects of the addition of Ca (100 and 200 g of gypsum per plant) to the substrate on the incidence of blossom-end rot (BER) in tomatoes cultivated by drip irrigation with water of 4.85 dS m-1 and high level of Mg salts (11.7 meq l-1) were studied, with and without the application by fertigation of a protein hydrolysate containing 87.6 g l-1 of organic N (with 13.2% of free amino acids). The addition of gypsum reduced BER at best by 50%. The concentration of Ca in fruit and leaves usually increased with the addition of gypsum, as did the Ca/Mg ratio. A highly significant correlation between BER incidence and Ca concentration in the distal portion of the fruit was found 10 days after anthesis, but not at full ripeness. Application of a protein hydrolysate by fertigation improved the reduction of BER, with a total absence of affected fruits in the first truss of those plants with 200 g of gypsum. The addition of the hydrolysate increased the content of histidine (17%), proline (15%) and alanine (11%) in ripe fruit. A highly significant correlation was found between the incidence of BER and the joint content of Ca and proline in the fruit.