Learning outcomes Soils Soil is made up of 5 main ingredients Soil is formed by a number of factors A soil profile consists of 3 horizons Ireland has 4 main soil types Soil and vegetation influence each other

Soil has 5 main ingredients both living and non-living Mineral matter Air Water Living Organisms Humus

Mineral Matter Mineral matter is the biggest ingredient in soil Consists of the remains of rocks that have been broken down into smaller particles by Weathering and Erosion It includes stones, sand, silt and clay

Air Air fills the pores between the mineral particles Air contains oxygen and nitrogen which are vital for the growth of plants Air allows living organisms to survive in the soil

Water Water helps bind the soil particles together Water contains dissolved minerals Plants absorb these minerals through their roots

Living organisms Soil is home to creatures such as earthworms, woodlice and slugs It is also home to micro organisms that include bacteria and fungi When worms burrow through the soil they mix it making it easier for water and air to pass through it Micro organisms help breakdown dead plants in humus

Humus Humus is the dark, partly decayed organic matter found in soil It is produced from the remains of dead creatures and plants These are broken down and mixed in the soil by the living organisms Humus provides nutrients that make the soil fertile It also helps to bind the soil particles together

Junior certificate exam question

How soils are formed A number of factors work together to form soil Climate Parent material Vegetation Living organisms Landscape Time

Climate Temperature and rainfall influence the rate at which parent rock is broken down by weathering Hot climates experience chemical weathering Cold climates experience freeze thaw

Parent material The type of rock in an area also affects soil formation Granite is slow to break down by weathering, while sandstone breaks down easily and forms soil quickly Soils that develop from limestone are more fertile than those that develop from granite and sandstone

Vegetation When vegetation dies, it is broken down and decays to add humus and nutrients to the soil Deciduous vegetation provides mire leaf fall than coniferous vegetation

Living organisms Micro organisms such as bacteria and fungi break down dead plant and animal life in the soil turning it into humus Animals such as earthworms dig through the soil breaking it up allowing more water and air to enter it When these creatures die, their remains add nutrients to the soil

Landscape Upland areas are cold and wet so soils are often water logged There is little plant life so there is less humus Lowland soils are generally deeper and well drained. They have more humus as there is a lot of plant and animal life

Time Time is one of the most important factors in soil formation The longer a rock is exposed to the forces of weathering, the more it is broken down It may take up to 400 years for 1cm of soil to form

Soil Profiles

A Horizon Also called the Topsoil Darker than lower layers as it has a high Humus content Most organisms live in this layer and it is the most productive layer

B Horizon Also called the subsoil. Usually lighter in colour as it has less humus More stones than A Horizon as it is closer to parent material and is protected from weathering

C Horizon Consists of Parent rock Upper section may be broken in rock particles Lower section is solid bedrock

Leaching

Leaching The process of leaching is when excess water washes minerals from the A horizon into the B Horizon If leaching is severe minerals such as clay and iron oxide(rust) build up at the bottom of the A horizon. The minerals get cemented to form a impermeable crust called a Hardpan, which may cause the soil above to become waterlogged Leaching can cause the A horizon to lose its fertility

Junior certificate exam question

There are 4 main types of soil in Ireland Brown earth soils Peaty soils Podzol soils Gley soils

Brown Earth Soils Developed after the last ice age on areas formerly covered by deciduous forest There was a plentiful supply of plant litter, which decayed to form humus giving the soil its brown colour Rainfall is limited so there is very little leaching Brown soils are fertile and suit a wide range of farming types Most common in Ireland in drier lowland areas of the South, Midlands and East.

Podzol Soils Developed in cold and wet areas covered by coniferous forests Limited amount of plant litter resulting in small amounts of Humus Heavier rainfall results in leaching causing a hard pan to develop which leaves the A Horizon with a grey colour Relatively infertile and slightly acidic Found in damp, poorly drained upland areas of Cork, Galway and Tipperary