Comparison of Three Equipment for Assessment of Soil Compaction.

Soil compaction has been widely reported as an important cause of crop yield loss due to its deleterious effect on plant root growth, soil water availability and water infiltration. The easiest way to assess soil compaction in large fields is by using soil cone penetrometers, which measure the soil resistance to penetration (PR). Such parameter is a measure of the soil strength and it is a good indicator of soil compaction when soil moisture conditions are near field capacity. In this study we evaluate the response of a manual dynamic (hammer) penetrometer (Kamaq, Brazil) and an automatic static penetrometer (SoloStar, Falker, Brazil) compared to a newly designed instrument (Saci Trail, Saci Soluções, Brazil), that is an automatic drilling soil sampler machine equipped with a pressure sensor, inside the hydraulic block (manifold), to measure the soil’s resistance to penetration. The study was conducted in a clayey soil (72% clay) under no-till and conventional tillage production systems (both with soybean in the summer and wheat in the winter). The dynamic penetrometer PR readings were overestimated by around 35% when compared to the static penetrometer, probably due to energy losses caused by the hammer impacts. The sensor pressure measured at the manifold increased as PR measured by both static and dynamic penetrometer increases, but it saturates for PR higher than about 2.5 and 3 MPa in the static and dynamic penetrometers, respectively. Results indicate a good potential for practical use of this new equipment, especially in precision agriculture applications, taking advantage of the soil-sampling task for fertility maps to also provide maps of soil compaction in large agricultural fields.