Improving the quantitative-qualitative characteristics and nutritional value of Kaleh Ghouchi pistachio by the foliar application of potassium and zinc

Pistachio is one of the most important horticultural products in Iran. In recent years, its yield and quality have been declined to some extent. One of the main reasons for the reduced yield and quality of pistachio is poor nutrition and deficiency of some nutrients. The present study aims at investigating the effect of foliar application of potassium and zinc on some quantitative-qualitative characteristics of Kaleh Ghouchi pistachio.

The experiment was conducted in a randomized complete block design with 9 treatments and 3 replications. Treatments included three levels of potassium sulfate (0, 1, and 2%) and three levels of zinc sulfate (0, 0.5, and 1%). The foliar application was conducted at two phases (swell bud and green tip stages).

The results indicated that nutritional treatments, especially the treatment with 1 or 2 % of potassium sulfate and 1% of zinc sulfate, resulted in significant increases in fresh weight (by about 44%) and dry weight (by about 41%) compared to those of the control. Moreover, nutritional treatments significantly affected the splitting percentage (a 10 % increase), while the blankness percentage was not affected; though its amount was lower in the nutritional treatments than the control treatment. In terms of fruit appearance, kernel appearance, and kernel taste, the highest quality was related to treatments with 1 or 2 % of potassium sulfate and 1% of zinc sulfate. Furthermore, nutritional treatments, especially the treatment with 2% potassium sulfate and 1% zinc sulfate, caused a significant increase in the amount of fat and carbohydrates in the kernel. Similarly, foliar application of potassium sulfate and zinc sulfate significantly affected the concentrations of potassium and zinc in pistachio kernels.

In calcareous soils of Iran, foliar application of potassium and zinc can be considered a practical nutritional program to achieve fruits with better quantity and quality in pistachio orchards.