Soil chemical extractions can alter potassium coordination in agricultural soils: A combined wet chemical and X-ray absorption spectroscopic approach

Soil wet chemical extractions are used to determine plant available potassium (K); yet problems with K bioavailability still persist in soils. Bioavailability is directly related how elements bonded and coordinated the solid phases of soil. However, there a critical knowledge gap respect identifying situ, solid-phase coordination environments soils treated extractions. Synchrotron-based X-ray absorption spectroscopy (XAS) measures molecular environment has been here study chemistry two agricultural field The objective this work pair XAS analyze changes throughout soil profile. profiles collected down 1.2 m loamy sand sandy clay loam were six different extraction methods: (1) Mehlich III, (2) ammonium acetate, (3 & 4) Haney, Hossner, Arnold 1 2, (5) citrate dithionite, (6) water extractable potassium. residual was analyzed using diffraction (XRD). Citrate dithionite extracted largest amount (1860 mg kg−1), removed least (30 kg−1). XRD indicate sources these illite, illite–smectite, smectite, feldspar. A Linear Combination Fit (LCF) approach indicated interest post-edge region K, K-edge XANES spectra due extraction. data that can remove loosely bound dislodge portion from interlayer space illite illite–smectite. This significant because effectively decreasing number coordinating O atoms surrounding causing dampening oscillations (3,620–3,650 eV). dislodgement III indicates inner-sphere bonds forms siloxane surfaces be broken, become more hydrated molecules also present space. dependent on texture, coarser textured soil, would an increased accommodation by montmorillonite or increase hydration resulted average intercalated spaces 25% samples according LCF results. Future studies involving sorption silicon aluminum oxides will further clarify behavior mineral surfaces, particularly during surface precipitation.