Changes

* Dull colours: <span style="color:#DAA520">'''yellows'''</span>, and <span style="color:#808080">'''greys'''</span>, often found together in mottled horizons indicate that the soil is not well drained and does suffer from prolonged saturation.  

* Dull colours: <span style="color:#DAA520">'''yellows'''</span>, and <span style="color:#808080">'''greys'''</span>, often found together in mottled horizons indicate that the soil is not well drained and does suffer from prolonged saturation.  

* <span style="color:#708090">'''Blue-grey'''</span> and <span style="color:#5F9EA0">'''blue-green'''</span> colours are a certain indication that the soil is saturated for most of the year. The colours are due to iron (normally red as oxide) being present in a reduced form (the opposite of being oxidised) and may be combined with sulphur, as a sulphide. Hence, such soils can often smell like bad eggs.

* <span style="color:#4682B4">'''Blue-grey'''</span> and <span style="color:#5F9EA0">'''blue-green'''</span> colours are a certain indication that the soil is saturated for most of the year. The colours are due to iron (normally red as oxide) being present in a reduced form (the opposite of being oxidised) and may be combined with sulphur, as a sulphide. Hence, such soils can often smell like bad eggs.

* Precipitation of iron compounds, usually <span style="color:#FF8C00">'''orange'''</span> or <span style="color:#B22222">'''dull red'''</span>, sometimes in association with manganese ('''black'''), is an indication of oxidation occurring in a generally waterlogged environment. Iron goes into solution in water that is low in oxygen, it can then be transported through the landscape until it reaches a more aerated zone when it precipitates. This iron movement process: solution, transport, precipitation/enrichment, is extremely common in soils and takes many different forms. It can occur as a groundwater discharge process, as a vertical leaching process of the upper part of the soil profile, or as a lateral (throughflow) process within the upper part of the soil profile. Concentrations of iron may occur as pans, as buckshot or ironstone and as laterite. The mottling of soils mentioned above occurs because of a more diffuse, small scale (a few centimetres) redistribution of iron within the material of the soil profile and the formation of iron hydroxides (<span style="color:#DAA520">'''yellow'''</span>).

* Precipitation of iron compounds, usually <span style="color:#FF8C00">'''orange'''</span> or <span style="color:#B22222">'''dull red'''</span>, sometimes in association with manganese ('''black'''), is an indication of oxidation occurring in a generally waterlogged environment. Iron goes into solution in water that is low in oxygen, it can then be transported through the landscape until it reaches a more aerated zone when it precipitates. This iron movement process: solution, transport, precipitation/enrichment, is extremely common in soils and takes many different forms. It can occur as a groundwater discharge process, as a vertical leaching process of the upper part of the soil profile, or as a lateral (throughflow) process within the upper part of the soil profile. Concentrations of iron may occur as pans, as buckshot or ironstone and as laterite. The mottling of soils mentioned above occurs because of a more diffuse, small scale (a few centimetres) redistribution of iron within the material of the soil profile and the formation of iron hydroxides (<span style="color:#DAA520">'''yellow'''</span>).

* <span style="color:#FFFFFF; background:#8B4513">'''White'''</span> colours in the subsoil are often due to the presence of calcium carbonate. This can be tested for using a little hydrochloric acid. If carbonate is present a few drops of acid will cause the soil to fizz and bubble as carbon dioxide is formed by the reaction of acid and carbonate. The depth from the ground surface to such a layer is often a good indication of the amount of leaching that has occurred throughout the formation of the soil.

* <span style="color:#FFFFFF; background:#8B4513">'''White'''</span> colours in the subsoil are often due to the presence of calcium carbonate. This can be tested for using a little hydrochloric acid. If carbonate is present a few drops of acid will cause the soil to fizz and bubble as carbon dioxide is formed by the reaction of acid and carbonate. The depth from the ground surface to such a layer is often a good indication of the amount of leaching that has occurred throughout the formation of the soil.