Changing the nature of the soil such that there is a decrease in the volume of voids between soil particles or aggregates; it is manifested as an increase in bulk density and a severely compacted soil can become significantly less permeable and less aerated. Manmade compaction is caused by poaching (trampling of animal hooves repeatedly) [...]
Increase in the amount of exchangeable Na of a soil (sodic soil = soil containing enough Na to negatively affect most crop plants by changing the physical soil properties).
Sealing of the (upper few cm) soil by the destruction of soil aggregates after wetting, causing a fine crust to occur, which reduces permeability of the soil and hamper seedling emergence.
Accumulation of soluble salts (more soluble than gypsum) in the upper soil layers (saline soil = soil containing enough soluble salts to negatively affect most crop plants, commonly 4000 μS m-1).
Decline of organic matter content in one or more soil layers when the annual loss of organic matter (e.g. due to oxidation or erosion) is insufficiently compensated for by the annual gain of organic matter, resulting from crop residues, composts and manures.
Increase of settlement areas over time. This process includes the development of scattered settlements in rural areas, the expansion of urban areas around an urban nucleus (including urban sprawl), and the conversion of land within an urban area (densification).
Accumulation of agents able to promote biological stress and subsequent loss of yield such as nematodes, weeds, microorganisms, mice, etcetera, favoured by, for instance, a too narrow crop rotation.
The gradual depletion of reserves of nutrients and organic matter in soils.
The wearing away of the land surface by water, wind, ice, gravity or other natural or anthropogenic agents that abrade, detach and remove soil particles or rock material from one point on the earth's surface, for deposition elsewhere, including gravitational creep and so-called tillage erosion.
The process in which relatively dry land becomes increasingly arid, typically losing its bodies of water as well as vegetation and wildlife either directly via climate change or indirectly via soil degradation resulting from poor management.
