Remote sensing of vegetation dynamics as an indirect assessment of soil compaction

Soil compaction is a major threat to global agriculture as it can affect crop production and negatively impact the environment. This can result in increased production costs, additional labor requirements and reduced time windows for field access. Nevertheless, the actual effects of soil compaction on the growth of different crops in different pedo-climatic regions are insufficiently investigated. In this study, possibilities for such assessments by remote sensing are evaluated in three pedo-climatic zones of Europe using a harmonized experimental design. Oceanic climate is subject in Belgium and The Netherlands, while in Austria a location with continental, drier climate and another location in an intermediate continental-hemiboreal climate are included.

By means of unmanned aerial vehicles (UAV) equipped with optical and multispectral cameras, plant-physiological indicators are surveyed frequently throughout the vegetation period. Examples for such indicators are crop height, vegetation cover and density, NDVI, and a set of further indices derived from the reflectance signature of the plants. Fields are monitored that partly underwent a defined and delimited compaction (headlands or wheel tracks from management using heavy machinery) and soil physical standard methods are applied to characterize the compaction state of the soils (e.g. bulk/packing density, soil penetration resistance). Differences in the listed indicators are analyzed between plants in compacted parts and the non-compacted areas closely nearby under the same growing conditions.

Results from the first year of observations revealed distinct differences between plant growth in compacted and non-compacted areas. Several indicators showed interesting patterns throughout the vegetation period, which will be subject of further in-depth analyses. In the continental climate and affected by an exceptionally dry winter, early stage development of winter wheat was even more vital in compacted areas. Further statistical analyses of the gathered datasets from the UAV- and in-field-observations will provide insights on whether information about the state of soil compaction and its effects on plant physiology are supposed to be derived from these surficial indicators.