Testing the Physical and Chemical properties of soils .

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3/8/2010

James Webber 12F

Mr. Reemeijer


1.0        Introduction

Different Soils types are important in determining which vegetation will grow in a particular environment, if any at all. There are a lot of characteristics of soils that are important in finding the amount of soil that could be found in that particular area. If these characteristics are known, introducing suitable plants for that particular area is far easier and in-term more successful. There is a multifaceted range or variety of materials in soils composition, including actions from weather on rock and biotic factors.

The materials from rock include clay, silt and sand. Sand is permeable and is very easy to identify however silt and clay are not. Silt is made from very fines particles therefore the texture of silt is very powdery. Clay is also composed of very fine particles. It is the result of chemical decay of rocks as their physical shape is worn down or corroded. Clay is also chemically active therefore its binds very easily to itself and other soil components, therefore if there is too much binding, the soil become hard and lumpy making it porous meaning it retains water. 

The biotic factors include humus and organic matter which is the material from the decay of once living organisms, both plant and animal. Organic matter arises when plants or animals die and the remnants remain in the soil which in-tern provides food for other small organisms which then die continuing the cycle.  Humus is formed once the original dead tissue is broken down and mixed into a tough and insoluble matter. Like clay, humus is chemically active and bonds itself to other soil components. Organic matter retains water and decreases the soils pH by adding acidic nutrients into soil.

Soil types are described according to their main components. Soil with a lot of clay in it is known as a clay soil; soil with a lot of sand in it is known as a sandy soil; soil with a lot of organic matter in it is known as organic soil, which is usually known as peaty soil and soil that has a good balance between clay, silt, sand and organic matter it is known as a loam.

Soil texture triangle

When clay and humus bond together, crumbs are formed which loosely bond with other neighbouring crumbs allowing small spaces to exist therefore allowing water to infiltrate through the soil. If there are large pores or spaces between the crumbs, water easily drains through the soil making the soil to be good in structure however if there are very small pores, water does not drain as easily making the crumbs stick together and the soil full of water resulting in heavy, wet, hard and lumpy making the soil poor in structure.

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Throughout South East Queensland there are a range of different crops which are grown for small cropping/ market gardening agriculture in a variety of different soils. These include beetroot, broccoli, cabbage, capsicum, carrots, cauliflower, celery, cabbage, garlic, lettuce, onion, peas, potato, sweet potato, pumpkin, corn, tomato and watermelon. These vegetables rely on the soil pH to be around 6-7.5, meaning they need a high percentage of organic matter in the soil and rely on good drainage, which means there needs to be a high percentage of sand in the soil.                                                                

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