Edaphic Factors

Edaphic factors are the properties of the soil that affect the organisms living in or on it. They are especially important for plants, which cannot move away.Soil texture. Soil is made of mineral particles of different sizes. Sandy soils have large particles and large air spaces: they drain quickly, are well aerated and warm up fast in spring, but hold little water, and mineral ions are easily leached out. Clay soils have tiny particles: they hold water and mineral ions well but drain slowly, can become waterlogged and poorly aerated, and are heavy to dig. Loam is a mixture and is usually the most fertile.Humus. Organic matter from decomposed organisms improves soil structure, holds water and releases mineral ions as it decomposes.Mineral ions. Plants need ions such as nitrate (for amino acids and nucleic acids), phosphate (for ATP, DNA and phospholipids) and magnesium (for chlorophyll). Soils low in these limit plant growth.pH. pH affects enzymes and the availability of mineral ions. Some species are adapted to a particular pH: heather grows on acidic soils, whereas many orchids and other chalk grassland plants grow on alkaline, chalky soils.Water and air content, which depend on the texture, drainage and humus.Soil also contains many organisms, such as earthworms, which aerate and mix it, and decomposers, which recycle nutrients. So edaphic factors are affected by biotic factors as well.