Soil compaction (agriculture)
This process can cause on-site effects such as reduced crop growth, yield and quality as well as off-site effects such as increased surface water run-off, soil erosion, greenhouse gas emissions, eutrophication, reduced groundwater recharge and a loss of biodiversity.
[4] Unlike salinization or erosion, soil compaction is principally a sub-surface problem and therefore an invisible phenomenon.
[6] However, multiple studies have shown that modern farming techniques increase the risk of harmful soil compaction.
[7] The historic data basis for global soil compaction is generally very weak as there are only measurements or estimates for certain regions/countries at certain points in time.
Not only may the weight of machineries i.e. axle load, but also velocity and number of passages affect the intensity of soil compaction.
[18][19] Inflation pressure of wheels and tyres also plays an important role for the degree of soil compaction.
This is because climate change features events such as heat waves and storms that can increase the risk of droughts and floodings and drainage systems.
When compacted soils are waterlogged or have an elevated water content, they tend to cause methane (CH4) losses to the atmosphere due to an increased bacteria activity.
The release of the GHG nitrous oxide (N2O) originates also from microbiological processes in soil and is reinforced by the use of nitrogen fertilizer on arable land.
More fuel and fertilizer are used for cultivation compared to uncompacted soil due to restrictions in crop growth resulting from a decreased efficiency in nitrogen use.
Except for direct negative effects for farmers, the risk of surface runoff close to wheel tracks affects the off-farm environment indirectly, as it for example redistributes "sediment, nutrients and pesticides within the field and beyond".
[38] On high risk areas, such as wet soils on slopes, applied slurry can runoff easily.
In regions where "the subsoil provides a significant proportion of the water required by crops to meet transpiration demands",[40] often being dependent on agriculture, this danger of compaction is most present.
Since the coarse pores are most important for water infiltration, gas exchange and transport, focusing on them when measuring the porosity and the diffusion coefficient is recommended.
Remote sensing helps to recognize alterations of soil structure, root growth, water storage capacities and biological activity.
"Detection of these features directly on the surface of bare soil or indirectly by the vegetation lead to identification of this type of degradation.
Since methods of remote sensing are not able to identify soil compaction directly there are limitations to identification, monitoring and quantifying, especially on a global scale.
[44] Since soil compaction is very hard to identify and reverse, special attention has to be paid on avoidance and alleviation.
In particular, member states committed themselves to "use and disseminate modern technology for data collection, transmission and assessment on land degradation".
[45] The European Union addresses soil compaction by means of the Seventh EU Environment Action Programme, which entered into force in 2014.
It recognises that soil degradation is a serious challenge and states that by 2020 land is supposed to be managed sustainably in the entire Union.
[46] National governments have regulated agriculture practices in order to mitigate the effect of soil compaction.
The law states that farmers have the obligation of precaution towards soil compaction according to acknowledged good practices.
[citation needed] The zaï technique[48] describes a system planting pits that are being dug into poor soil.
Agroforestry systems aim at the stabilization of the annual yield as well as the healthy maintenance of the ecosystem by combining the cultivation of crop plants and trees on the same site.
[50] Technical methods mainly aim to reduce and control the pressure applied on soil by heavy machinery.
[51] Expected is a reduction of area compacted by tyres, reducing negative effects on crop growth.
