Document Type : Research Paper
Authors
1
Former MSc. Student of Soil Science, Yasouj University
2
Associated Professor, Department of Soil Science, Faculty of Agricultural Sciences, University of Yasouj, Iran.
3
Assistant Professor of Soil and Water Research Department, Kohgiluyeh-va-Boyerahmad Agricultural and Natural Resources Research and Education Center, AREEO, Yasouj, Iran.
10.22092/ijsr.2025.368579.769
Abstract
Potassium plays a vital role in improving both the quantity and quality of agricultural products. However, a considerable amount of potassium in the soil is present in non-exchangeable and structural forms, making it less accessible for plant uptake. In recent years, citrus production has become increasingly important worldwide as a major source of economic growth, trade, and employment. This study investigated the various forms of potassium in the surface and subsurface soils of orange orchards located in Fars (10 orchards) and Kohgiluyeh and Boyer-Ahmad (8 orchards) provinces. Additionally, it sought to identify an appropriate extractant for measuring plant-available potassium in these soils. 36 soil samples were collected from 18 orchards at two different depths. The analysis included various potassium forms, such as soluble, exchangeable, non-exchangeable, structural, and total potassium. Moreover, leaves from one-year-old branches were gathered to assess their potassium concentration. Potassium extraction was conducted using 11 different extractants, including 1M and 2M sodium chloride, 0.01M calcium chloride, Morgan, ammonium bicarbonate-DTPA, 1M ammonium acetate, 1M sodium acetate, 0.1M nitric acid, 2M hydrochloric acid, 0.025M sulfuric acid, and 1M magnesium acetate. The correlation between extracted potassium and plant uptake in orange trees was then evaluated. The findings indicated that the 2 M hydrochloric acid extractant had the highest correlation with the potassium absorbed by the plant. Furthermore, according to the soil potassium standard threshold, only three orchards in Fars and three in Kohgiluyeh and Boyer-Ahmad had potassium levels exceeding the critical limit. Leaf analysis also revealed that 60% of the samples from Fars orchards and 25% from Kohgiluyeh and Boyer-Ahmad orchards contained potassium levels below the sufficiency threshold. Thus, in most orchards, applying potassium fertilizers, is crucial for maximizing crop yield.
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