Submitted to: Encyclopedia of Water
Publication Type: Book / chapter
Publication Acceptance Date: 10/23/2004
Publication Date: 12/1/2005
Citation: Corwin, D.L., Lesch, S.M. 2005. Characterizing soil spatial variability. The Encyclopedia of Water (Volume 5). J.H. Lehr. (ed.) John Wiley & Sons, Inc. New York, NY. pp: 465-471. Interpretive Summary: Soil spatial variability refers to the tremendous change in soil (physical, chemical, mineralogical, and biological) properties that is found in nature. The change in soil properties over time and space has tremendous influence on any soil-related issue from the variation in crop yield that a farmer sees to the complex fate and movement of contaminants in the environment. A concise discussion is presented of the definition, origin, significance, and means of characterizing soil spatial variability. In particular, emphasis is placed on the description of characterizing spatial variability with the measurement of soil electrical conductivity, which is mapped out across a field using a global positioning system. The maps of electrical conductivity show the scientist where to take soil samples so that the spatial variability of a variety of soil properties can be mapped out. Maps of spatial variation in soil properties can ultimately provide farmers, consultants, and scientists with information concerning the movement of pollutants, how the quality of the soil is changing, or where and how much fertilizer or water to apply to improve crop yield. This article is part of the Encyclopedia of Water and is intended to provide the general scientific audience with a basic understand of how soil spatial variability is characterized.
Technical Abstract: Soil spatial variability refers to the variation in soil physical, chemical, mineralogical, and biological properties across the landscape and through the soil profile. The significance of soil spatial variability lies in its direct or indirect influence on any landscape-scale soil-related issue ranging from solute transport of non-point source pollution to precision agriculture. A general discussion of the origin, need for characterization, and measurement methods is presented with greatest emphasis placed on the use of apparent soil electrical conductivity (ECa) to characterize spatial variability. The characterization of spatial variability with geospatial ECa measurements is based on the correlation of ECa with various physico-chemical properties and the use of ECa-directed soil sampling designs. Edaphic factors influencing ECa measurements, mobile ECa measurement equipment, ECa-directed sampling designs, guidelines for conducting an ECa survey, and limitations and precautions are discussed. The discussion is intended to provide a basic understanding of spatial variability and its characterization with geospatial ECa measurements to a general scientific audience.