Chapter 3 Agriculture and the environment.pdf

3. AGRICULTURE AND THE ENVIRONMENT 3.1 Soil composition Mineral particles: combination of rock fragments and other inorganic substances. They are formed due to physical, chemical and biological weathering of the parent rock. Organic content: mixture of living plants, animals, micro...

3. AGRICULTURE AND THE ENVIRONMENT 3.1 Soil composition Mineral particles: combination of rock fragments and other inorganic substances. They are formed due to physical, chemical and biological weathering of the parent rock. Organic content: mixture of living plants, animals, microorganisms and their dead remains. Air: held within the pore spaces (between the mineral particles and organic content). Air enters the soil by diffusion. Water: held within the pore spaces (water that is available for plant growth). Water enters the soil when there’s precipitation or when the soil is irrigated. The proportion of these components depends on: o Type of soil; o Way it has been managed; o Local climatic conditions; o Size of the mineral particles. Soil can be classified into three groups: TYPE SIZE TEXTURE Sand 2.0-0.02 mm Gritty. Silt 0.02-0.002 mm Silky or soapy. Clay