Alleviation of salinity - Induced stress in cash crops by Multi-K (potassium nitrate), five cases typifying the underlying pattern

The use of enhanced potassic plant nutrition is an efficient method of preventing sodium-induced stress in many crops. In addition, the use of enhanced nitrate fertilization is a potent tool in precluding chloride-induced stress in many crops. The application of Multi-K (potassium nitrate) is shown here as a very efficient method of combating the aforementioned stresses and enhancing crops performances under saline conditions. This concept is validated shown here for five moderately salinity-sensitive crops representing the three main sectors of agriculture: A) sweet corn for annual field crops, B) citrus for perennials, and C) tomato, lettuce and Chinese cabbage for greenhouse-grown vegetables. By adding Multi-K to their nutrition program, these crops were better able to cope with salinity conditions despite higher EC levels resulting from this treatment. The incorporation of Multi-K at 2, 8 or 14 mM in the nutrition scheme of salinized sweet corn significantly increased dry matter production and ear yield. Salinity treatments (6.6 - 18 mM of Cl-) markedly increased Cl and Na contents of grapefruit leaves, thereby reducing the total yield of the trees and their canopy volumes, but had a minor effect on K content of the leaves. By maintaining a constant concentration of 2 mM Multi-K in the irrigation water, the adverse effects of salinity treatments on the trees were avoided. The resulting yields increased from 3 to 38%. Salination (50 mM NaCl) of the nutrient solution of greenhouse tomatoes markedly decreased K content of the leaves, fruit-set rate, number of flowers, dry weights of the plants, fruit sizes and stem heights. Adding Multi-K at 2,4 or 8 mM to the salinized nutrient solution reversed these effects, despite marked increase in EC. Moreover, several vegetative parameters were improved over the non-salinized controls. Three levels of Multi-K (1, 5 and 10 mM) were tested on salinized (52 mM of Cl-) hydroponically grown lettuce and Chinese cabbage. The highest yields of fresh weight of both crops were obtained from the 5 mM Multi-K treatment, under both saline and non-saline conditions. Salination increased the concentration of Na and Cl in plant tissue and reduced the levels of N and K; the opposite occurred in plants fed by the medium and high levels of Multi-K. All the aforementioned results clearly demonstrate that plants can successfully cope with stresses imposed by 30-50 mM Na and Cl, by continuous application of Multi-K at 2-8 mM. A general model can explain all phenomena involved.