- Slides: 22
Leaving Certificate Agricultural Science Soil 5 – Soil Groups
The General Soil Map of Ireland � This was first published in 1969, with a second edition in 1980. � These show the distribution of the major soil groups throughout Ireland (and each county also) as well as a discussion on their land use potential. � The major soil groups • • • a. The Podzols b. Brown Podzolics c. Grey – brown Podzolics d. Brown Earths e. Gleys f. Rendzinas g. Lithosols h. Blanket peats i. Basin Peats
Soil Groups � Because of the huge variety of rock types in Ireland there is a huge variety of soil types. � The ordinance survey of Ireland has classified ~15 great groups. � Four of these are of agricultural importance. Grey Brown Podzolics: Top quality soil type very desirable. 2. Brown Earths (acid) : Top quality soil type very desirable 3. Gleys: Intermediate quality 4. Podzols: Poor quality 1.
Soil Profiles � These are gotten by digging down vertically into a soil to its parent rock and looking face on at the different layers. � Profiles using the colour, texture and depth of a soil tell us all the properties of that particular soil. �Horizon (Peat) only appears in Podzol. It is made up of Organic Matter. �A Horizon – Topsoil �B Horizon – Subsoil �C Horizon – Parent Rock
Profile of a Grey Brown Podzolics – top quality A 1 Earthworm activity has increased OM causing dark colour (3 -6 cm) A 2 Mature* well drained mineral soil. High C. E. C. – fertile, good friability (5 -7 cm) B 1 Has a slightly darker colour due to translocation of clay fraction. This is a horizon of enrichment. Texture is heavy or blocky. C This is calcareous rock (limestone). It is permeable (porous). Generally there is never a drainage problem.
Profile of a Grey Brown Podzolics – top quality *Maturity –relatively stone free. � This soil is used extensively for tillage (malting barley). Most crops are grown under contract for the 2 major breweries (Guinness and Murphy’s).
Profile of a Brown Earth (Acid) – Top Quality
Brown Earths A 1 This is a mature welldrained mineral soil – well-aerated sand, silt and clay, friable, good structure, good root penetration (60 cm) A 2 Accumulation of leached calcium ions C Calcareous parent material –limestone – porous and permeable
Profile of a Brown Earth (Acid) – Top Quality � These soils are mature, well drained mineral soils. � They have not suffered from serious cases of leaching (loss of minerals) � They have a uniform profile (i. e. No distinct horizons or layers) � The Brown Earths in Ireland are mainly found in areas where the underlying rock is acidic, and therefore the soil is acidic.
Profile of a Brown Earth (Acid) – Top Quality � With regular liming and fertilising the soils can be quite a productive soil. � Brown earth soils have an extensive use range, however they are used mainly for grazing. � They are the soils of the Golden Vale – East Limerick, South Tipperary, Waterford, and North and West Cork, and are all excellent producers of grass for the liquid milk market.
Profile of a Gley Soil
Profile of a Gley Soil A 2 Thin layer of topsoil Accumulation of OM darkened colour. gives B Accumulation of clay particles. Blue-grey in colour and has mottles of Fe. Leaching is not a feature. Texture is heavy due to capillary water trapped by clay particles – structure less. C Generally impermeable sandstone rock.
Profile of a Gley Soil � Gley soils form on areas of rolling lowland or gentle sloping hillsides. � They suffer from frequent water logging (West of Ireland 205 rain days annually). � They develop of impermeable parent rock and suffer because of excess run off from higher ground. � Gleys have a limited use range.
Profile of a Gley Soil � They are confined mainly to summer grazing. � Stock will have to be removed during the winter to prevent poaching. � However with careful draining and liming the potential of this land is hugely increased e. g. mole drains (15 cm deep)
Profile of a Podzol soil – very poor
Profile of a Podzol soil – very poor O A layer of organic matter. If it exceeds 30 cm it is referred to as a blanket bog. Sphagnum moss grows here (can absorb ~10 X its own weight in water). Here there anaerobic conditions. B 2 A very poor subsoil – very strong Bir Impermeable iron pan – behaves like a perched water table C Generally an acid rock. Typical example – old red sandstone.
Profile of a Podzol soil – very poor � If water logging or flooding occur, then little or no oxygen will be available and organic matter will eventually form an O Horizon. � This is the first stage of a formation of a peat and the soil is now known as a Peaty Podzol. � When the O Horizon becomes deeper than 30 cm, then the soil is no longer podzol, but is now a blanket peat.
Profile of a Podzol soil – very poor � Podzols are not very useful as tillage soils, or for grazing. � This is due to their poor drainage and poor root penetration. � It has an extremely limited use range. It is confined almost exclusively to forestry (conservation). � Where it is used for agriculture – commonage – but they suffer from severe leaching when overgrazed.