Spatial and fractal characterization of selected soil nutrients along a catena

Abstract

Soil nutrient elements influence crop productivity and environmental sustainability and they vary across several slope positions. The objective of the current study was to evaluate the spatial and fractal variability of selected soil macro- and micronutrient elements across five slope positions: summit, shoulder, back, foot, and toe slopes. Triplicate soil samples (0–18 cm) were collected from each slope position from a pasture field planted to tall fescue (Festuca arundinacea syn. schendonorus arundinaceus). Soil nutrient elements analyzed include phosphorus (P), potassium (K), nitrate N (NO3-N), iron (Fe), and manganese (Mn). Additionally, soil pH, bulk density (BD), and soil organic carbon (SOC) were determined. Results show that SOC was 26% higher, while BD was 10% lower at the toe slope compared with the summit. Similarly, NO3-N was 15, 16, 18, and 1% higher at the toe slope position compared with the summit, shoulder, back and foot slopes probably due to nutrient mobility with water flow. Semivariogram analysis showed that the gaussian isotropic model provided be best fit (R2 > 0.97) for all nutrient elements across all slope positions. The range of spatial variability (A0) of nutrient elements was between 5.8 (K at the backslope position) and 71.0 m (P and Fe at the shoulder and back slope positions, respectively). The fractal dimensions of soil nutrient elements across all slope positions ranged from 0.216 to 1.949 suggesting that as the sampling distance exceeds half the A0, soil nutrient elements tend to become self-similar. The variability in soil nutrient elements from the current study can serve as a useful nutrient application recommendation tool for precision agriculture across five slope positions.