the problem

Farmers know that healthy soil is one of the most important factors behind high yields and long-term profitability. However, soils are under threat nowadays due to soil compaction. Around 1980, a tractor weighed an average of about 6 tonnes. Today, the average tractor's weight is around 9.5 tonnes.

We see here a weight increase of more than 60% in 40 years. At the same time wheels and track systems have developed, but the bottom line still is that compaction has become one of the urgent problems to coop with. The good news is that compaction can be controlled.

But before we go further we need to understand the problem a little bit more. Compaction decreases yields but also damages soil health in the long run. Moreover, it can lead to emissions of nitrous oxide, which is not good for climate.

To put it simple, soil compaction has five negative effects on the soil. See the figure.

First, compaction affects root development of plants. Root development requires cavities in the soil (macropores) to develop positively. Soil compaction means that the soil becomes more compressed than is biologically desirable, which i.a. means that the roots of the crop can not develop as easily into the soil.

Second, compaction affects water flows. The capillary forces decrease and the soil is then unable to carry water from the lower layers up to the growing crop. Another problem concerns the reverse direction. If not surface water can get down through the soil, the water stays at the surface.

Third, compaction affect nitrogen processes. As the soil becomes poorer in oxygen, nitrification processes are inhibited, ie. the conversion of ammonium to nitrate. As ammonium, through its positive ionic charge, binds to the small negatively charged clay particles in the soil (the colloids), the ammonium tends not to move as well in the soil as the nitrate and this means that the crop does not capture the nutrients.

Fourth, compaction harms the biological life. A number of organisms ensure that organic materials in the form of plant residues or biofertilizer are broken down into smaller constituents, which are then converted into nutrients that the plants can assimilate. The first stage of this is done by e.g. earthworms and beetles. Soil compaction makes the conditions worse for e.g. the earthworms.

Fifth, compaction affects oxygen access. If the soil is low in oxygen, anaerobic bacteria will thrive. Some of these convert nitrate to nitrogen gas and nitrogen oxide (nitrous oxide). Both nitric oxide and nitrogen gas then disappear into the atmosphere. Thus, the soil loses nitrogen which could have contributed to the development of crops. In addition, nitrous oxide is negative for the climate.

Research has shown that the packing on the topsoil and the subsoil (the lower soil layer) are different. The upper soil layer is affected by both the weight and the footprint area. However, the lower soil layer (subsoil) is affected almost exclusively by the load ie. gravity.

The Compaction Prevention System (CPS)

The Compaction Prevention System (CPS) enables continuous and automatic monitoring of expected soil compaction given every specific situation regarding load, vehicle footprint, soil type, moisture and other factors.

CPS also enables overview of fields and help future planning of driving in the fields. Thus, people responsible for driving vehicles at farms can make the right decision to minimize soil compaction – both in real time and as part of planning. The system can also be equipped with an alarm function, which is activated when a certain level of soil compaction risk is exceeded