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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.

Article InfoThe present study was conducted to explore the fractal behavior and establish fractal dimensions of soil physical and chemical properties (i.e., sand, silt, and clay contents, bulk density, degree of moisture saturation, pH, organic carbon content, total nitrogen, available phosphorus, and available potassium) to characterize their spatial patterns. Soil samples were collected from 0-30 (surface) and 30-60 cm (subsurface) depths from an agricultural field, Mashhad Plain, Northeast Iran. Descriptive statistics and fractal analysis were used to describe the extent and form of variability. Spatial patterns of the soil properties were estimated using GS+ 10.0 software. Soil properties showed low to high variations in both surface and subsurface layers across the field, where bulk density and pH being the most reliable soil physical and chemical properties in the study area. The variability was high (CV > 35%) for total N, available P, available K and organic carbon in both surface and subsurface soils and it could be attributed to management practices and micro-topographical variations as these are the dynamic properties of soil. The fractal dimension (D) values of soil physical properties ranged from 1.398 to 1.913 at the surface, and from 1.874 to 1.934 at the subsurface indicating both short and long range variations. The D values for the chemical properties ranged from 1.331 to 1.975, and 1.148 to 1.990 in the surface and subsurface layers, respectively. The results showed that fractal analysis could be employed to effectively describe the structure of soil heterogeneity in spatial scale for effective agricultural and environmental management of soil.

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