A spatially and temporally high-resolution 4-year soil compaction risk analysis at field scale

Soil compaction due to intensive field traffic is one of the main threats to agricultural soils. Besides lower biomass productivity, compacted soils have a reduced regulation function which affects the air, water and nutrient cycles. To evaluate and mitigate soil degradation by field traffic, it is important to know where, when and to what extent soil compaction may occur during certain work processes.

For this purpose, we modelled and analysed the soil compaction risk for each work process during a 4-year crop rotation (winter wheat, maize, winter wheat, sugar beets) for one field in Lower Saxony, Germany. Based on RTK-GPS tracks recorded by the farm machineries, FiTraM (field traffic model) was used to model the spatial representation and the wheel load for each tire of each work process. Subsequently, these data were used for the soil compaction risk assessment by the SaSCiA-model (Spatially explicit Soil Compaction risk Assessment). In total, 63 work processes were modelled with a spatial resolution of 20 cm.

The model results revealed that the soil compaction risk at field scale is highly variable in space and time. The spatial variations in soil compaction risk are mainly determined by the spatial distribution of soil properties like soil texture, carbon content and soil moisture. In combination with changing wheel loads, e.g. during harvest processes, the soil compaction risk ranges from low to extremely high during one work process. The temporal variation is mainly caused by the weather conditions. A prolonged period with low precipitation resulted in no subsoil compaction risk during maize harvest, although maize harvest is often a major cause of soil compaction.

This study shows that the soil compaction risk varies in a wide range within a certain field. Efforts to mitigate soil compaction should consider spatio-temporal dynamics at high resolution to achieve a sustainable soil management.