Pedogenic processes and soil–landform relationships for identification of yield-limiting soil properties

Knowledge of soil–landform relationships helps in understanding the dominant pedogenic processes causing variations in soil properties within and between landforms. In this study, we investigated how major pedogenic processes in three landform positions of the semi-arid Deccan Plateau (India) have led to current plant yield-limiting soil properties. For this, we characterised 26 pedons from three landforms – piedmont, alluvial plain and valley – and performed factor analysis on the dataset. As the frequency distribution of the dataset was highly skewed for most of the soil properties, landform-wise partition and log-transformation were performed before studying soil variability within landforms. Results indicated that two factors explained 56, 71 and 64% of variability in soil properties in piedmonts, alluvial plains and valleys, respectively. The major soils in lower piedmonts (Typic Haplustalfs and Typic Rhodustalfs) were spatially associated with Vertisols (Sodic Haplusterts) occurring in alluvial plains and valleys. The soil properties in alluvial plains and valleys (Vertic Haplustepts, Sodic Haplusterts and Typic Ustifluvents) were modified due to regressive pedogenic processes. These soils were characterised by high pH (8.5–9.8), exchangeable sodium percentage (16.5–46.6) and poor saturated hydraulic conductivity (<1cmh–1). Subsoil sodicity induced by the presence of pedogenic calcium carbonate impaired the hydraulic conductivity. Subsoil sodicity and poor saturated hydraulic conductivity were identified as major yield-limiting soil properties. The relationships found between specific soil properties, surface and subsurface horizons, and position in the landscape helped to determine the dominant pedogenic processes and how these influenced current soil properties and their effects on crop yield.