ADLib Glossary (S)

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Soil Terminology

Soil biological activity

The activity of soil micro-organisms and other soil life such as worms helps to break down organic material and so release plant nutrients into the soil.

Soil contamination

Soil is vulnerable to contamination from a variety of sources. In the majority of cases remedial treatment is not realistic on financial grounds and consequently crop yields may be drastically reduced. Possible sources of contamination include:

  • Pesticides and fertiliser residues building-up in the soil.
  • Contamination from flooding, especially by sea water.
  • Heavy metal contamination from industrial emissions, from sewage sludge applications to the soil or from the application of pig slurry generated from pigs fed with a diet containing high concentrations of these metals.
  • Or by accidental spills of chemicals (including agrochemicals), oils, farm wastes, etc.
  • As well as reducing the fertility of the soil other factors should also be considered.
  • The value of the land could be affected.
  • If human health is affected, you could be sued.
  • Ground and surface waters could become contaminated.

Soil degradation

This usually refers to the loss of organic matter and/or the deterioration of the soil structure. Soil organic matter is a vital component of productive and stable soils. It provides plant nutrients and improves water retention. Many factors can cause soil degradation These include intensive farming, repeated cultivations, soil compaction and a reduction in the use of organic manures. The loss of organic matter on a global scale has been identified as a contributory factor towards global warming as the organic carbon is ultimately converted to carbon dioxide increasing the levels in the atmosphere.

Soil respiration and nitrogen turnover

Soil respiration is a measure of microbial activity in the soil and therefore is a measure of the rate of organic matter turnover and nutrient cycling rates in soil.

Nitrogen fertiliser usually contains nitrogen in one of three forms - ammonium, nitrate or urea. Once added to the soil, soil enzymes and microbes rapidly convert any urea and ammonium to nitrate. Nitrate is also produced from the breakdown of soil organic matter and from any manure or plant residues. Nitrate is very soluble in water and so is readily leached out of the soil by water draining through it. It may also be lost to surface waters by run-off, through land drains and to groundwater by deep percolation.

Plants absorb the nitrogen they need as ammonium or nitrate. The term nitrogen turnover is used to describe how much nitrogen was released from the soil, how it is lost and when this nitrogen release occurred.

Soil tramlines

These are paired continuous plant free strips, designed to allow the passage of a tractor with sprayers and fertiliser distributors without damaging the crop. Tramlines are an integral part of modern high input cereal production and necessary to allow high traffic through standing crops, especially at the later stage of crop growth.

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