A Study of the Quantity/Intensity Relationships of Potassium in Some Calcareous Soils of Iran

Abstract

Exchangeable potassium (EK)determined by NH₄OAc may not be a reliable indicator of the soil potassium (K⁺)available to crops in soils containing micaceous minerals. Potassium quantity-intensity relationships (Q/I) can be used to predict K⁺ availability to plants in these soils. These relationships were used to study K⁺ supplying capacity of 15 calcareous soils of Hamadan, western Iran. Equilibrium concentration ratios (CR₀) varied from 0.022–2.49 × 10⁻⁴ (mol l⁻¹)^1/2. The potential buffering capacity (PBC) values ranged between 23.3–170.5 cmol_c kg⁻¹/(mol l⁻¹)^1/2 and the readily desorbed or labile K⁺(EK₀) varied from 0.02–0.64 cmol_c kg⁻¹, which represented an average of 49.2% of the EK. According to free-energy values, most soils are classified as medium to deficient in K⁺. Parameters of Q/I relationships were correlated with some chemical and physical properties of soils. There was a significant correlation (significant at 0.05 probably level) between EK and CR₀ (r = 0.83) as well as EK₀ (r = 0.84), and between EK₀ and CR₀ (r = 0.89). There was not significant correlation between PBC and cation exchange capacity (CEC) and clay content. The Q/I parameters provide useful information for understanding K⁺ availability in calcareous soils and can be used for K⁺ fertilizer recommendations.

Keywords:

• calcareous soils
• Iran
• potassium
• quantity/intensity

Two anonymous reviewers made valuable comments on the manuscript. The author gratefully expresses his gratitude for their thoughtful reviews.

Notes

^a OM: organic matter.

^b EK: exchangeable K.

^c EPP: exchangeable potassium percentage (EK/CEC).

^a 1 = most abundant, 6 = least abundant

All coefficients of determination are significant at 0.1% probably level.