Effects of the Timing of Foliar Application and Concentrations of Growth Regulators on the Mineral Content of Pistachio Leaves

Pistachio is one of the economically important horticultural crops in Iran. The main pistachio-producing areas in Iran are located at the edge of the desert and are affected by soil and water salinity. Water and nutrient uptake by the root decreases under saline conditions. In this study, the effects of foliar growth regulators applied at different times on the nutrient uptake and leaf nutrient content of pistachio trees were examined in accordance with a split-plot experimental design based on a randomized complete block design with three replications. The field experiment was conducted with a group of 30-year-old pistachio trees that have been exposed to water and soil salinity. Experimental factors included the timing of foliar application and the applied concentrations of plant growth regulators. The timing of foliar application was the main factor and was split into three levels: application on May 21th, June 21th, and May 21th + June 21th. Different concentrations of plant growth regulators, including sodium nitroprusside, salicylic acid, and jasmonic acid, were split into ten levels and were designated as the sub-factor. Results showed that the timing of application and the applied concentration of plant growth regulators affected root nutrient uptake and leaf nutrient content. The one-time application of plant growth regulators in June and the two-stage application of plant growth regulators in May and June resulted in the highest increase in leaf nutrient content compared with the control treatment. The application of low and moderate concentrations of plant growth regulators increased leaf nutrient content compared with the control treatment. High concentrations of plant growth regulators exerted no significant effects on leaf nutrient content.