Table of Contents
In this three main edaphic factors of ecosystem post we have briefly explained about edaphic factors refers to, soil formation, soil types, edaphic factors which affect vegetation, soil profile, and types of soil particles.
Edaphic Factors Refers to
Edaphic factors refers to, the abiotic factors related to soil, include the physical and chemical composition of the soil formed in a particular area. The study of soils is called Pedology. The soil is the weathered superficial layer of the Earth in which plants can grow. It is a complex composite mass consisting of soil constituents, soil water, soil air and soil organisms, etc.
Soil originates from rocks and develops gradually at different rates, depending upon the ecological and climatic conditions.
Soil formation is initiated by the weathering process. Biological weathering takes place when organisms like bacteria, fungi, lichens and plants help in the breakdown of rocks through the production of acids and certain chemical substances.
Based on soil formation (pedogenesis), the soils are divided into 1. Residual soils –These are soils formed by weathering and pedogenesis of the rock. 2. Transported soils – These are transported by various agencies.
Edaphic factors which affect vegetation
Soil moisture: Soil moisture conditions affect plant root water absorption and leaf transpiration, which further affect dry matter accumulation, and ultimately affect crop yield.
Soil water: Soil water is more important than any other ecological factors affecting the distribution of plants. Rain is the main source of soil water. Capillary water held between pore spaces of soil particles and angles between them is the most important form of water available to the plants.
Soil reactions: Soil may be acidic or alkaline or neutral in their reaction. pH value of the soil solution determines the availability of plant nutrients. The best pH range of the soil for cultivation of crop plants is 5.5 to 6.8.
Soil nutrients: Soil fertility and productivity is the ability of soil to provide all essential plant nutrients such as minerals and organic nutrients in the form of ions.
Soil temperature: Soil temperature of an area plays an important role in determining the geographical distribution of plants. Low temperature reduces use of water and solute absorption by roots.
Soil atmosphere: The spaces left between soil particles are called pore spaces which contains oxygen and carbon-di-oxide.
Soil organisms: Many organisms existing in the soil like bacteria, fungi, algae, protozoans, nematodes, insects, earthworms, etc. are called soil organisms.
Soil is commonly stratified into horizons at different depth. These layers differ in their physical, chemical and biological properties. This succession of super-imposed horizons is called soil profile.
Types of soil particles
Soil can be defined in many ways. In civil engineering, soil is a naturally occurring, loose/un-cemented/weakly cemented/relatively unconsolidated mineral particles, organic or inorganic in character, lying over the bed rock which is formed by weathering of rocks. Soil is formed by different particles such as gravel, rock, sand, silt, clay, loam and humus
It is most extensively used construction material. It consists of particles of rock and hard minerals, such as silicon dioxide. They are the largest type of soil particles, where each particle is visible to naked eye. The large, relatively stable sand-particle size increases soil aeration, improves drainage in tight soils and creates plant-growth supporting qualities, or tilt.
he particle size of course sand ranges from 2 – 4.75mm, Medium sand ranges from 0.425 – 2 mm and fine sand ranges from 0.075 – 0.425 mm. The bigger particle size of the sand gives wet or dry sandy soil a grainy texture when you rub it between your fingers, and it makes the soil light and crumbly even when you try to stick it together in your hand. The particle shape is angular, sub angular, rounded, flat or elongated. The texture is rough, smooth, or polished.
Silt is a sediment material with an intermediate size between sand and clay. Carried by water during flood it forms a fertile deposit on valleys floor. The particle size of silt ranges from 0.002 and 0.06 mm. Silt is a non-plastic or low plasticity material due to its fineness.
Due to its fineness, when wet it becomes a smooth mud that you can form easily into balls or other shapes in your hand and when silt soil is very wet, it blends seamlessly with water to form fine, runny puddles of mud.
Clay particles are the finest of all the soil particles, measuring fewer than 0.002 mm in size. It consists of microscopic and sub-microscopic particles derived from the chemical decomposition of rocks.
Clay is a fine grained cohesive soil. They stick together readily and form a sticky or gluey texture when they are wet or dry. Clay is made of over 25 percent clay, and because of the spaces found between clay particles, clay soils hold a high amount of water. Clay expand when in contact with water and shrink when getting dry.
Compared to sand particles, which are generally round, clay particles are thin, flat and covered with tiny plates. Organic clay is highly compressible and its strength is very high when dry, which is why it is used in construction as mud mortar.
Loam is a mixture of clay, sand and silt and benefits from the qualities of these 3 different textures, favouring water retention, air circulation, drainage and fertility. These soils are fertile, easy to work with and provide good drainage. Depending on their predominant composition they can be either sandy or clay loam. The way the other particles combine in the soil makes the loam.
For instance, a soil that is 30 per cent clay, 50 per cent sand and 20 per cent silt is a sandy clay loam, with the soil types before “loam” listed in the order their particles are most dominant in the loam. The labels “clay loam,” “silt loam” and “sand loam” are used to refer to soils that are composed predominantly of those ingredients.