Effects of Irrigation-based Potassium Fertilizer on Leaf and Nut Nutrients of Two Pistachio Cultivars

The annual consumption of soil potassium by pistachio trees is high. Since the clay soil absorbs potassium, the amount of potassium that can be exchanged or used by the tree in the soil solution is little, and every year this deficiency must be compensated by fertilizers. To evaluate the role of potassium in improving the nutritional elements of the leaves and nuts of two pistachio cultivars (‘Ahmad-Aghaei’ and ‘Kalleh-Qoochi’), four levels of potassium fertilizer were used (0, 200, 300 and 400 mg of potassium per liter of irrigation water) in a factorial experiment in the form of a randomized complete block design with three replications. This experiment was performed on the ON and OFF branches in 2017 and 2018. The results showed that the application of potassium increased the amounts of nutritional elements in the leaf and nut. Specifically, the amounts of nitrogen, phosphorus and potassium were higher in the leaves of OFF branches, whereas the concentrations of calcium and magnesium were higher in the leaves of the ON branches. In both cultivars, the application of potassium increased the amounts of nitrogen and phosphorus in the leaf, as well as the potassium content in the nut. The amounts of calcium and magnesium in the leaf and the amount of calcium in the nuts were higher in the Kalleh-Qoochi cultivar. This treatment can be recommended when plants are in their OFF year, so that potassium can be reserve into the tissues until the ON year.