The process of covering of a soil by buildings, or types of artificial material which may be very slowly permeable to water (e.g. asphalt or concrete). Soil sealing can cause rapid overland flow after precipitation where water cannot soak away leading to potential flooding. A soil is unable to function effectively when sealed.
Accumulation of nutrients, metals or organic compounds leading to a reduction of the capacity of soils to deliver soil functions. Contamination may have a direct toxic effect on the plants, animals or humans living in, on, or from that soil, or have an indirect toxic effect due to accumulation in the whole trophic chain.
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.
