Layering 
The formation of a distinct layer within a soil profile. Mostly this is due to the use, or misuse, of top-dressings: See Soil Layering. Aerating a surface to a consistent depth without varying the depth will also result in a layer developing; this is also called an Aeration Pan.
Leaching
The action of water, in the form of rain and irrigation, washing nutrients in a soil solution through a soil profile. High sand profile constructions and excessive irrigation or rainfall increase the potential for leaching. The leached nutrients find their way through drains and soil horizons to pollute water courses, including aquifers.
Lime Requirement
The quantity of calcium carbonate needed to raise a specified quantity of soil from one pH level to another pre-determined pH level. Typically, the calculation for many agricultural crops is to raise an acidic soil up to pH 6.5 to encourage maximum yield. This is not an aim for turfgrass swards, but altering soils in the soil cultivation stage might be considered for a very acidic soil on which a perennial ryegrass sports surface is to be produced.
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