Litter Layer

Part of the Organic Horizon which is mainly consists of undecomposed plant material, typically leaves, but also including basal sheaths and twigs if on wooded areas of trees or shrubs. Also called the L Horizon/Layer/Zone.

  Loam Soil Class

A soil that is a medium textured soil with a relatively balanced blend of sand, silt and clay particles, but there can actually be a fairly wide difference between some of the particle percentages. An example of a loam soil is one that contains the following: 45% sand, 35% silt, 20% clay. This soil class is usually quite suitable for general lawns, parks and playing fields, due to its moisture holding ability and retention of nutrients, as well as fairly good drainage capabilities when well maintained. There is not a stand-alone loam textural class in the UK Soil Textural Triangle as this is m

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  Loamy Sand Soil Class

A soil with a range of different particles - sand, silt and clay - but which is more on the rough to gritty side, rather than having an excess of fine particles. An example of a loamy sand soil is one that contains the following: 77% sand, 13% silt, 10% clay. It is generally suitable for lawns and some sports turf situations, although it might be too free draining in drought prone areas that have limited access to irrigation facilities.

  Loss on Ignition

A laboratory method of burning off organic matter within a soil sample to determine the soil organic matter content. An air-dried soil sample placed in a furnace and typically heated to 500C for 4-hours, or longer. The difference in mass between the original sample and the residue is the percentage content of organic matter that has been oxidised. The formula used for calculating the percentage loss is (Original air-dried mass (g)-mass after heating in furnace (g) )/(Original air-dried mass (g)) x 100% = Organic matter % A worked example where 7g is lost during burning

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  Macropore

Relatively large pore spaces in a soil that are greater than either 0.05mm or 0.075mm in diameter, depending on the classification used. Macropores are created by plant roots and soil fauna such as earthworms, nematodes, fungi, and bacteria. Increasing the amount of macropores within a soil improves drainage and aeration., with them often being air-filled at field capacity, in contrast to mesopores or storage micropores which will retain water at this stage.

  Marl

A dense chalky clay loam soil, with about a 30% content of clay, and which was a reddish-pink colour due to the presence of the mineral hematite, iron oxide (Fe2O3), within the soil. It was originally proposed, in 1939, by the MCC that the inclusion of marl within a top-dressing mixture could be used and that this became a popular ingredient in the topdressing for preparing cricket pitches, being especially popular during the 1950s to 1970s. A guide application rate was equivalent to about 0.54-1.1kg/m2, ideally being mixed in with 3.3-5.4kg of clay loam soil to give an overall application

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  Mechanical Weathering

See Physical Weathering.

  Mesopore

Intermediate sized soil pores ranging from 0.005mm to either 0.05mm or 0.075mm in diameter, depending on how it is classified. These are also termed Storage Micropores as they retain water that is available for a plant.

  Micropore

Small soil pores typically found within soil aggregates. Water does not drain naturally from micropores (as natural drainage to field capacity occurs with macro-pores) and can be considered as being those which retain water and which are gradually depleted of water as this is used by plants via evapo-transpiration. The classification size of a micropore can vary, being less than 0.075mm, or 0.05mm, in diameter; to no smaller than 0.0002mm for what are termed Storage Micropores or Mesopores; whilst any micropore less than 0.0002mm is classed as a Residual Pore and the water retained in these is

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  Moder

An intermediate type of humus, between Mor and Mull. It has intermediate levels of biological activity and a slightly acidic soil condition, with the organic horizon of the soil profile typically having distinct layers of Litter (at the surface), overlying a Fermentation layer.