Two-dimensional prediction of spatial variation in topsoil compaction of a sandy loam field-based on measured horizontal force of compaction sensor, cutting depth and moisture content

The development of a topsoil compaction map, based on real-time measurement of the draught (D) of a compaction sensor provides a quick view of positions of extremely compacted zones. The measured D of a subsoiler, used as a compaction sensor was utilised to draw the two-dimensional spatial variation in soil compaction of a sandy loam field (Arenic Cambisol). On the basis of a previously developed formula, dry bulk density (ρd) indicating soil compaction was estimated as a function of the measured horizontal force, cutting depth (d) and moisture content (w). This formula was the output of a numerical–statistical hybrid modelling scheme, which aimed to estimate the variation in sensor D as a function of w, d and ρd. The ARCVIEW 3.1 GIS software was used to draw the field maps of measurement and model-based ρd, d, w. The measurement and model-based ρd ranged from 1343 to 1750 and from 1271 to 1523 kg m−3, respectively. The model-based ρd was underestimated by a mean error of 14%. A comparison of measurement and model-based ρd maps indicates a similar tendency of spatial variation in soil compaction, particularly positions of extremely compacted zones. This allows providing the farmer with a compaction map, which illustrates the extreme zones of soil compaction. A correction factor of 14% in ρd is incorporated into the developed numerical–statistical model, which improved the magnitude of the model-based predicted soil compaction. Furthermore, the real-time measurement of w with better control of d might be helpful to improve the magnitude of ρd predicted and spatial distribution of soil compaction.