Soils

Investigating Soils



Soil is the upper layer of earth in which plants grow, a black or dark brown material typically consisting of a mixture of organic remains, clay, and rock particles.

 

Soil Structure

 

 

Soil structure refers to the arrangement of soil separates into units called soil aggregates. An aggregate possesses solids and pore space. Aggregates are separated by planes of weakness and are dominated by clay particles. Silt and fine sand particles may also be part of an aggregate.

 

Soil Types

 

All soils are made up of 5 components, sand, silt, clay, organic matter (and humus) and Minerals (nutrients). The percentage of each component determines the soils ability to drain, to hold water, to hold nutrients, maintain life, determine Acidity and maintain structure.

 

 

Sandy Soils
Sandy soils have a higher percentages of sand. Sand is a large soil particle that can't be broken down any smaller, they are large, round grains and when they fit together they leave large ‘pore’ spaces or gaps between them. In soils, large pore spaces fill with air and not water. So, we can say that sandy soils have large gaps which hold air and allow water to flow down through them, providing for good soil drainage.

Sandy soils are:

• Full of large air holes.
• Free Draining soils
• Is easy to work with (light)
• Dries out quickly
• Minerals are easily leached. (Keep reading to find out what leaching is)
• Lower in nutrients.
• Faster to warm up in spring.

Clay Soils
Clay soils are the opposite of sandy soils. Clay soils have a high percentage of clay. Clay particles are small, flat and sticky particles. They fit tightly together, which means that in clay soils there are only small ‘pore’ spaces or gaps between the particles. Small pore spaces are better at holding water and not good at holding air. Therefore, we can say that clay soils hold a lot more water than air.
Clay soils are also sticky and help bind soils together to form larger soil clumps. Most soils in the midlands of Ireland are made up of 50% clay. Clay soils hold water and therefore hold nutrients so are all highly fertile.

Clay soils are:

• Better at holding water
• Wetter and heavier soils
• Harder soils to work in wet conditions
• Naturally fertile soil.
• More fertile as leaching of minerals is slower
• Very poor drainage, which can lead to water logging.
• Is a cold soil
• Darker in colour

Silt Soils
Silt soils have a higher percentages of silt particles. Silt particles are basically smaller sand grains and therefore the pore spaces between the particles in smaller than that of sandy soils. Silts are common result of floodplains and are consider highly fertile. Also because they are smaller than sand and larger than clay they have a good balance of pore space sizes.
Silt soils are not a common soil type in Ireland.

Silt soils are:

• Good at retaining water
• Slower draining than sandy soils
• Fertile soils

Loam soils
Loam soils are the perfect balance of each soil mentioned above. They have half-way characteristics of both clay and sandy soils, with more advantages and fewer disadvantages.
While structure, drainage and workability of soil depends on its composition, the amount of organic matter is also a major factor, which influences fertility, worm content and acidity.



Peat soils
Peat soils have a high percentage of Organic matter. Organic matter is partially decomposed plant and animal material that has been broken down over thousands of years. Organic matter is in high concentration in peat areas because peat bogs are damp and sufficient oxygen for decomposition to take place, this leads to a build up of organic material.

Peats soils can be found in the midlands as well as around the west and North west of the country.

Peat soils are:

• High in organic matter
• Dark in colour
• Depth soils
• Have a higher fertility
• Poor draining
• Acidic soils

Leaching

Natural process by which water soluble substances (such as calcium, fertilizers and pesticides) are washed out from soil. These leached out chemicals cause pollution of surface and sub-surface water.