Edaphic Factors

The factors concerned with the soil are called edaphic factor. The soil is the upper layer of the earth which provides nutrients, water supply, anchorage to the plants. It is the mixture of inorganic matters and organic matters. Inorganic matters are derived by weathering process whereas organic matters are derived from the decomposition of dead remains.

Inorganic portion of soil varies in size which is named as:

• Clay (0.002m less)
• Slit (0.002-0.02)
• Fine sand between (0.02 to 0.2)
• Coarse sand (0.2-2)
• Gravel (more than 2)

The relative properties and the arrangement of soil particles in the soil are called soil texture. On the basis of soil texture, soil are of three types:

• Sandy soil
• Clay soil
• Loam soil

Sandy soil

It contains about 80 or more than 80% of sand and other remaining portions are silt and clay. The particles of sandy soil are loosely arranged and more porous. Water loading capacity is low and the nutrients are very poor in level.

Clay soil

It contains about 50% of clay and remaining portions are silt and sand. The particles of the clay soil are compactly arranged and the water holding capacity is very high. Moderate amount of nutrients is found. The penetration of roots in this type of soil is very difficult. The aeration is low.

Loam soil

Loam soil contains 20% clay, 40% sand, and 40 % silt. This type of soil contains more nutrients, air, and water. It is considered as the best soil for the growth of the plants.

Influence of edaphic factors on organism

• Soil air is essential for the respiration of soil organisms. It is also necessary for the respiration of underground parts of the plants like roots etc. It also plays an important role in seed germination.
• The soil water is essential to supply nutrients and minerals in the plants. The soil water determines the types of plants like xerophytes, mesophytes, hydrophytes etc. It also plays a vital role in distribution and abundance of plants. It is essential for seed germination. It also protects the soil organisms from dying.
• Soil temperature is very important for the survival of both plants and animals. If the temperature is high or low, it affects soil organisms. It is also important for seed germination.
• Soil organic matters or humus makes the soil loose, fertile and porous. Humus provides all the essential nutrients to the plants. It determines the distribution and abundance of plants and animals in an area. It increases the water holding capacity and aeration of the soil.
• Soil organisms such as bacteria, fungi etc. play an important role in the fertility of the soil. Earthworm increases the fertility of the soil or makes the soil loose by adding excretory matters. Some of the bacteria in the soil like rhizobium bacteria fixes the free atmospheric nitrogen into nitrates and increases nitrogen in the soil.
• Soil pH effect in the growth, development and distribution of plants.