Micropenetrometer for In Situ Measurement of Soil Surface Strength

Soil surface characteristics greatly influence seedling emergence, water infiltration, and soil erosion. A portable micropenetrometer was designed to measure the strength of the soil surface (or crust) as an indirect measure of soil surface characteristics in the field. The penetrometer is designed to operate on a 12 V DC battery and is controlled by a portable microcomputer. Penetrometer measurements can be made a few millimeters apart along 1‐m long transects with a small (1.6 mm) probe in order to evaluate spatial patterns of crust strength. Laboratory and field measurements show that the penetrometer is capable of detecting detailed differences in the nearsurface soil (0–4 mm depth) that result from different physical, chemical, and management‐related conditions. Penetration measurements from 0 to 30‐mm depth at 0.1‐mm depth increments reflected differences in the structure of the surface soil layer due to irrigation method by detecting sequences of aggregates and pores as the probe penetrated the soil. These results indicate that the micropenetrometer is capable of detecting and quantifying differences in soil surface characteristics influencing physical processes at the soil surface.