Soil: Spatial Variability

Abstract

Spatial variability occurs at all scales—from micrometer scale (1–10 µm) relevant to microbial processes to continental scale (1000 km) relevant to the distribution of soil orders and climate change. The order of magnitude of the coefficient of variation (CV) of soil properties ranges from a few percent to greater than 100%. Jenny’s soil forming factors, climate, topography, organisms, parent material, and time, represent the fabric of the natural variability of soil that is modified by anthropogenic properties resulting in a complex distribution of soil characteristics. Very small scale soil property variations may affect biological and chemical processes and may even explain soil ecological puzzles such as the high level of functional redundancy and diversity of soil biota. Spatial and temporal variations in soil properties may affect the spatial distribution of important soil processes. The spatial analysis of these variations is often done using semivariance analysis and mapping with kriging, an unbiased, optimal interpolation technique developed for estimating ore deposits from limited field data. Variable rate agriculture, in which GPS technology is used to map crop yield, uses spatial analysis to predict spatially explicit fertilizer applications to improve yield and lower environmental impacts. Spatial analysis is also used in environmental management, environmental modeling, and a multitude of research investigations. All applications need to consider the patterns and scale of variations in order to obtain accurate estimates of the variability of soil properties and processes.