Evaluation of an On-the-go Soil Strength Profile Sensor Using Soil Bin and Field Data

Abstract

An on-the-go soil strength profile sensor (SSPS) has been developed to measure the within-fieldspatial variability in soil strength at multiple depths up to 50 cm. In this paper, performance of the SSPS wasevaluated using soil bin and field data. First, the SSPS was tested in a soil bin at different depths (10, 20, and30 cm), forward speeds (from 0.5 to 3.0 m s-1), and compaction levels (high and low). Second, field data werecollected from two fields having variable bulk density, water content, and soil texture. Prismatic soil strengthindex (PSSI, defined as force divided by the base area of the horizontally operating prismatic tip) and coneindex were measured at five depths (10, 20, 30, 40, and 50 cm) in entire fields and also more intensively in four10-m by 10-m areas, selected for soil texture differences. Auxiliary data collected were bulk density, soil watercontent, and apparent soil electrical conductivity (ECa). When the SSPS was tested in the soil bin, increases inPSSI with speed were less than 15% up to a 3.0-m s-1 operating speed. We selected 1.5 m s-1 as a criticalspeed, below which effects on PSSI would be negligible, for field data collection. Mean PSSI values collectedin adjacent, parallel transects were not statistically different, confirming the repeatability and stability of soilstrength sensing with the SSPS. Field data showed that, in general, PSSI was higher at locations with lowerECa and water contents, and greater bulk density values. Results of stepwise multiple linear regression showedthat variability in PSSI was better explained when interactions among the soil variables were included asindependent variables and when data were grouped into subsets by depth and/or ECa level. Over entire fields,R2 values for estimating PSSI were 0.61 and 0.52 for a claypan soil field and a flood plain soil field,respectively. These results will be useful for interpretation of PSSI and for future applications of the SSPS incrop management, e.g., delineation of highly-compacted within-field areas and control of variable tillageoperations.