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 cmolc kg−1/(mol l−1)1/2 and the readily desorbed or labile K+(EK0) varied from 0.02–0.64 cmolc 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.