Major Ion Chemistry of Soil Solution of Mountainous Soils, Alvand, Hamedan, Western Iran

Abstract

Soil solution chemistry reflects the most dynamic processes occurring in soils and is responsible for their current status. This study was undertaken to determine the soil solution status in 25 mountainous soils. The major cations in the studied soil solutions are in the decreasing order of Ca²⁺ > Mg²⁺ > Na⁺ > K⁺. The anions are also arranged in decreasing order as HCO⁻ ₃ > Cl⁻ > NO⁻ ₃ > SO ²⁻ ₄ . Concentrations of NO⁻ ₃ , P, and K⁺ in soil solutions were in the range of 12–364 mg l⁻¹, 1.75–34.8 mg l⁻¹, and 0.78– 198 mg l⁻¹, respectively. Results suggest that the concentration of P in the soil solutions could be primarily controlled by of the solubility of octacalcium phosphate and ß-tricalcium phosphate. In general, the greater the dissolved P concentration in the soil solution, the closer the solution was to equilibrium with respect to the more soluble Ca²⁺ phosphate minerals. Surface soil accumulations of P, NO⁻ ₃ , and K⁺ have occurred in these soils to such an extent that loss of these nutrients in surface runoff and the high risk for nutrient transfer into groundwater in concentrations exceeding the groundwater quality standard has become a priority management concern.

Keywords:

• Soil solution
• nitrate
• phosphorous
• calcareous soil