Evaluation of soil development and weathering intensity of shrink-swell soils within the Painganga valley, Yavatmal district, Maharashtra, India

Effective crop management in shrink-swell soils is constrained by the limited understanding of the chemical weathering processes influencing soil evolution in the Painganga valley. This study examined seven types of shrink-swell soils in the valley using physical, chemical, and geochemical analyses. The soils are moderately to strongly alkaline and display calcium carbonate accumulation in subsurface horizons, with dominance of calcium and magnesium in the exchange complex. Nutrient analysis reveals poor to marginal fertility, with widespread deficiencies in nitrogen, phosphorus, and DTPA-extractable zinc. Elemental analysis showed silicon as the most abundant oxide (mean 23.53%), followed by aluminium (8.82%) and iron (6.2%). The high molar Si/Al ratio (> 3) and low K/Al ratio (< 0.2) indicate a significant amount of smectitic clays. The Herron diagram suggests that iron-rich sands are the primary sediment source. Correlation analysis revealed a moderate correlation between iron and titanium (r = 0.53**) and a strong relationship between iron and aluminium (r = 0.80**), indicating possible formation of iron-titanium hydroxides derived from alumina. One-way ANOVA results showed significant differences among soil groups for the fine clay to total clay ratio, mAl/mSi and mSi/mFe ratios, and weathering index (W₁). Migration coefficients indicated substantial depletion of silicon, aluminium, iron, and potassium in endogenic horizons due to moderate weathering and profile homogenization. The Si vs. Al + K + Na plot reinforces the role of the semi-arid climate in pedogenesis while preserving paleoclimatic signatures and the valley’s complex geological history.