5. Physical Properties of soils done.docx

Physical Properties of Soil Mineral Matter such as parent rock material is broken down into mineral particles. These mineral particles are in order of size gravel, coarse sand, fine sand, silt and clay. Organic Matter is the breakdown of dead plants and animals when it decomposes it is then called h...

Physical Properties of Soil Mineral Matter such as parent rock material is broken down into mineral particles. These mineral particles are in order of size gravel, coarse sand, fine sand, silt and clay. Organic Matter is the breakdown of dead plants and animals when it decomposes it is then called humus. The four main properties of Soil are texture, structure, porosity, chemistry and colour Physical Properties of Soil are measured by the different-sized minerals such as sand, silt, clay that are found in a soil sample. The amount of sand, silt and clay will determine the texture of a soil and the amount of drainage available to the soil. A loam soil has the same amounts of sand, silt and clay. How to use the soil triangle? Calculate the percentage sand, silt and clay in a soil by using a soil sieve or by sedimentation. Mark the percent clay and draw a line across the triangle parallel to the side marked ‘% sand’. Mark the percent silt and draw a line across the triangle parallel to the side marked ‘% clay’. The area in which these two lines intersect gives the name of the soil texture. Soil Structure is the where the particles of soil are in the soil itself. A Micro-pore is the term for the pore space within an aggregate and whether it's different in the units of aggregate. (Aggregate is when silt, sand and clay are held together by colloidal particles) this is known as flocculation. Soil Texture taking a handful of dry soil and adding water to is will show the type of texture. Roll it into a ball if it crumbles its sandy soil. If it makes a ball its clay. Good soil structure is necessary for the drainage of excess water, allows air ro move in the soil, roots to grow and allows water to be held in the soil. Structural Development of Soil Cementation is the binding of soil particles. Separation is when the aggregates in soil are broken and cracks form. How flocculation occurs: Chemical reactions in the soil cause the formation of negative charges on the soil colloids. Cations are attached to these charges and are absorbed onto the surface of the soil colloids. The colloids are linked together by the polarised water, and this is known as floccule. Soil porosity is the amount of soil pores in soil and whether there filled with air or water. Around 50% of soil should have soil pores. Soil Air has less oxygen and more carbon as roots and earthworms absorb oxygen and release carbon. This is known as diffusion. Soil aeration can be helped by avoiding poaching of the land, adding farmyard manure which will increase earthworm activity and adding lime Soil Water needs large pores for drainage while small pores are needed for water retention for plant growth. Example, large pores in sandy soil will cause drought in good weather. Small pores in clay soil will cause waterlogging. Soil Colour id dark when it has more sunlight and light coloured in low nutrient areas. Soils that are black or brown are high in humus. Red colouring is a sign of leeching. Soil Temperature is critical crops grow easier and faster in warm soils and can be stunted in cold soils.