| Overview | Details | Data Sources | Links | References |
| Soil Formation | • | Soil Characteristics | • | Soil types in Ireland | • | Soil Organisms | • | Soil Erosion |
 Soil particles mixed with rocks. |
As the parent material accumulates, mosses, lichens and other lower plant forms gradually appear and add to the developing soil as they die, generating a layer of humus. Higher forms of plant life are able to establish themselves as more and more humus accumulates. Living organisms such as earthworms, bacteria, fungi and nematodes also contribute to the development and enrichment of the soil by mixing and adding nutrients to the soil. The topography of the land is another important factor in soil formation as it helps determine how much rainfall will run off the surface, and also affects the average temperature of the soil, depending on whether or not the slope is in the shade for most of the day. Time is an important consideration since the soil forming factors must act for a considerable period (up to hundreds of thousands of years) to develop a soil profile with well expressed soil horizons.
| Sieve Columns | |
Separated sediment sample constituents from left to right: Stone and Seashell mix, Sand and Silt mix and Clay (mud) |
Sieve Columns determine
the composition of terrestrial or aquatic sediments. They establish
the proportion of coarse, medium and fine material by sorting sediment
samples using several sieves.  |
Organic matter in the soil is made up of living and dead organisms. Microorganisms living in the soil, such as bacteria and fungi, decompose animal and plant material and recycle nutrients. The stable product of decomposed organic matter is called humus and forms the top layer of many soils, providing the nutrients that plants need. The particles in the soil are held together by moist clay, organic matter and by fungal hyphae, which together form soil aggregates. Water and air is held in the pores between these soil aggregates.
Leaching process: In this process the soluble elements in the soil are washed downwards as a result of waterflow in the soil. These elements may be lost to the top layers of soil.
Gleisation: This process results from restricted water movement in the soil, also known as water logging. It occurs in soils with a high water table or where the chemical property of the soil is not permeable. In waterlogged soils, lack of oxygen causes the reduction of iron and a display of a grey to blue colour.
Calcification: During this process calcium carbonate is redistributed in the soil, without its complete removal. It is mainly the result of low rainfall and calcium carbonate is accumulated at some point in the soil profile. The climate in Ireland prevents the calcification of Irish soils on a large scale but this process takes place to a smaller extent creating base rich soils.
Soil
Characteristics
Soil Colour: Spatial variation in soil colour through the soil profile distinguishes different soil horizons and provides an indirect measure of important soil properties including drainage, aeration, organic matter content, as well as some of the chemical processes occurring beneath the surface. Generally, dark brown or black soils are associated with high levels of organic matter.Soils frequently saturated with water will often be a light gray or blue colour because iron and manganese particles have been leached away.
Soil Texture:
Soil texture refers to
the relative proportion of sand, silt and clay size particles in a sample
of soil. Sand and silt
are the products of physical weathering while clay is the product of
chemical weathering. A soil is allocated to a textural class, depending
on its content of sand, silt and clay sized particles. A textural triangle
diagram can be used to determine texture if particle size distribution
is known, or to determine a range of particle size distributions if
texture is known.
Soil Structure: Soil structure refers to the arrangement of soil particles formed by natural processes into aggregates or peds and can affect water movement, aeration, heat transfer, porosity and root development within the soil. The dominant shape, size and strength of the aggregates determine their structural type. There are four principle types of soil structure: Spheroidal, Platy, Block-like and Prism-like.
Soil - pH: The soil pH is an indication of the acidity or alkalinity of a soil solution. Soil pH has a profound effect on the solubility of minerals and nutrients and therefore on plant growth. It affects the types and quantities of micro organisms available in the soil, such as certain forms of bacteria which help decompose organic matter and release vital nutrients such as Nitrogen into the soil.
Soil types in Ireland
Soils can be distinguished from
weathered parent material by different layers, called horizons. Horizons
are displayed horizontally in a soil profile and have different properties
such as colour and chemical makeup, owing to the soil forming processes
and their interactions.
Letters identify the horizons within the soil profile. The uppermost layer is the O or the Organic horizon, consisting of large amounts of organic material in varying stages of decomposition. Below is the A horizon (topsoil), containing a mixture of inorganic minerals and organic matter. This is the zone where most biological activity occurs, as many soil organisms such as worms, nematodes, bacteria and fungi exist here often in close association with plant roots. The next layer is the B horizon (subsoil) where most of the iron, aluminium, clays and other leached material (from the A horizon) have accumulated. Under this layer is the C horizon, the transition zone between soil and parent material, followed by the R horizon, the layer of partially-weathered bedrock at the base of the soil profile.
The soils in Ireland have been classified using a modification of an
American soil classification system that has been applied in the United
States by the Department of Agriculture since 1938. The ten main soil
groups in Ireland are:
Soil Colour: Spatial variation in soil colour through the soil profile distinguishes different soil horizons and provides an indirect measure of important soil properties including drainage, aeration, organic matter content, as well as some of the chemical processes occurring beneath the surface. Generally, dark brown or black soils are associated with high levels of organic matter.Soils frequently saturated with water will often be a light gray or blue colour because iron and manganese particles have been leached away.
Textural Triangle of the USDA System (Image Source: Wayne Newbill ) |
Soil Structure: Soil structure refers to the arrangement of soil particles formed by natural processes into aggregates or peds and can affect water movement, aeration, heat transfer, porosity and root development within the soil. The dominant shape, size and strength of the aggregates determine their structural type. There are four principle types of soil structure: Spheroidal, Platy, Block-like and Prism-like.
Soil - pH: The soil pH is an indication of the acidity or alkalinity of a soil solution. Soil pH has a profound effect on the solubility of minerals and nutrients and therefore on plant growth. It affects the types and quantities of micro organisms available in the soil, such as certain forms of bacteria which help decompose organic matter and release vital nutrients such as Nitrogen into the soil.
Soil types in Ireland
 Part of a soil profile on a building site. |
Letters identify the horizons within the soil profile. The uppermost layer is the O or the Organic horizon, consisting of large amounts of organic material in varying stages of decomposition. Below is the A horizon (topsoil), containing a mixture of inorganic minerals and organic matter. This is the zone where most biological activity occurs, as many soil organisms such as worms, nematodes, bacteria and fungi exist here often in close association with plant roots. The next layer is the B horizon (subsoil) where most of the iron, aluminium, clays and other leached material (from the A horizon) have accumulated. Under this layer is the C horizon, the transition zone between soil and parent material, followed by the R horizon, the layer of partially-weathered bedrock at the base of the soil profile.
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- Podzols: these poor, acidic soils are formed in hill and mountain areas; they are grey in colour and low in humus and can be found in Counties Wicklow, Donegal and Kerry.
- Brown Podzolics: these soils are similar to the Podzols but less depleted; they have a good mix of mineral and organic matter in the surface layer and can be found in Counties Cork, Waterford and Tipperary.
- Brown Earth: these mature, well drained soils with a uniform, brown soil horizon show high fertility and can be found in Counties Clare, Wexford and Wicklow.
- Grey Brown Podzolics: these soils are formed on calcareous parent material, which counteracts leaching processes; they are all-purpose soils and can be found in Counties Meath, Westmeath and Kildare.
- Gleys: these soils developed under waterlogged conditions; they mostly show poor physical conditions and are grey/blue in colour and can be found in Counties Monaghan, Cavan and Leitrim.
- Blanket Peats: these soils have accumulated in areas of high rainfall and have poor drainage capacities; they have a characteristic high organic matter content, which can be over 30 percent and are at least 30 cm deep; they can be found in Counties Galway, Mayo and Sligo.
- Basin Peats: these soils have formed in hollows, river valleys or lake basins under conditions where the subsoil is not permeable; there are two types: raised bogs and fen peats; they can be found in County Longford.
- Redzinas: these shallow soils are not more than 50 cm deep and can be found together with Lithosols in Counties Dublin and Clare.
- Lithosols: these soils are very stony and are situated over solid or crushed bedrock and can be found together with Redzinas in Counties Dublin and Clare.
- Regosols: these soils show no horizon development and lack the B-horizon and can be found in County Waterford.
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Soil Organisms
 Exposed Soil and Roots in a New Ditch. |
Mainly plants provide organic matter, while fungi and bacteria consume and decompose it. In this way, the living organisms in the soil recycle nutrients, such as carbon and nitrogen.
Waste, in and on the soil, that ranges from dead plants to synthetic chemicals, is crunched, buried and decomposed. Soil organisms also provide porosity, which is necessary for ventilation in the topsoil.
The size and type of the creatures varies greatly from tiny bacteria to massive tree root systems. However, the number of the smaller creatures is the greatest: between one and ten million microorganisms are present in every one gram of soil. They are living in the soil water, on the plant litter surfaces and in the minerals of the upper soil horizons.
| Facts on Soil Biota |
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Soil Erosion
Soil conservation is fundamental for the survival of life. Up to 90% of our food production depends, in one way or another, on soil. We are stretching this resource considering the world population is already over 5 billion with a yearly increase of 100 million.
 Removed vegetation cover in a field caused by overgrazing and trampling. |
In Ireland, soil erosion can be observed when soil gradually moves down a slope in a field and finally rests against a hedge or ditch. After heavy rainfall, reddish-brown, swollen rivers can be noticed that carry fertile soils out to the sea. This water contains an increased nutrient content, which can damage the balance of nutrient poor, aquatic ecosystems by shifting their species composition, supporting more nutient-loving species. This can lead to the eutrophication of rivers and lakes. If contaminated soils are eroded and transported to the sea, aquatic plants and animals can be severely damaged.
 Eroded Pathways at the Cliffs of Moher. |