Estimating the Spatial Distribution of Soil Penetration Resistance in a Field as a Function of Water Content and Bulk Density

Abstract

Penetration resistance is a soil property directly affecting plant growth. For site specific management, the information about the spatial variation of penetration resistance can be used for managing tillage practices and irrigation schedules. The spatial variation of penetration resistance in a field is dependent upon bulk density and water content. The degrees of penetration resistance could be expressed by the function of bulk density and water content. The objective of this study is thus to model the relationship between penetration resistance versus bulk density and water content and to evaluate the spatial variation of penetration resistance as a function of bulk density under various water content levels. Geostatistics was used for analyzing the spatial variation and for mapping penetration resistance. The field experiment was conducted on the alluvial plain of the Choshui River in Changhua County, Taiwan. The textural class of soils is sandy loam. The in situ measurements of penetration resistance were carried out using the cone penetrometer. The soil samples were also taken for measuring bulk density and water content. The results indicated that the soil penetration resistance was significantly correlated with bulk density and water content. The penetration resistance decreased with increasing water content but increased with increasing bulk density. The relationship model between penetration resistance and bulk density under a specific range of water content was also developed. Based on the relationship model under a specific range of water content and the spatial distribution of bulk density, the contour maps of soil penetration resistance under various water content levels can be generated. The spatial distribution of penetration resistance is useful for managing irrigation schedule and tillage practices in a specific region.