Evaluation of Soil Quality Index of Surface and Soil profile in Pistachio Orchard of Bajestan, Notheastern Iran

Pistachio is one of the important export products, strategic and compatible with dry environments in Iran. The objective of this study was to evaluate the soil quality index of pistachio orchards at different geomorphic surface (no-saline clay flat, saline clay flat, intermediate alluvial fan- non-saline clay flat, intermediate pediment- saline clay flat) in two layers of soil surface (horizon A) and soil profile (0-150 cm), and its effect on pistachio yield in Bajestan playa. For this purpose, 12 soil profiles were investigated in different geomorphic surfaces. The soil physical and chemical properties of the soils were measured. The minimum data set (MDS) was determined by principal component analysis (PCA) method and the soil quality index was calculated by additive and weighted methods. The results showed that in good orchards, the weighted soil quality index was higher than the additive soil quality index both in surface and soil profile in all geomorphic surfaces. The soil quality index had the lowest value in saline clay flat geomorphic surface, both in surface soil and soil profile, due to the accumulation of soluble salts, high groundwater level and being in the margin of the salt crust. The weighted soil quality index showed a strong correlation with tree yield both in surface soil especially soil profile. Based on the results, it is necessary to improve the soil quality not only in the surface soil, but also in the deep layers, to achieve the desired and sustainable yield of pistachi in the region.