Organic Matter in the soil | Kothari Group

Organic Matter In The Soil

Date: 29-09-2021

The amount of organic matter present in the soil varies depending on the type of soil. In cultivated soils, it varies from less than 1% to about 15%. In peat soils, their percentage can go up to 90% to 100%. The amount of organic matter is usually high (5% to 15%) in soils formed in temperate, cool, and humid regions, but their amount is low (1% to 2%) in soils of the arid and semi-arid regions. This difference occurs due to the fact that the decomposition of organic matter is faster in cool regions than in warm regions. In tropical humid regions, where the temperature and rainfall, are high, the amount of organic matter in the soil is usually higher than in the arid and semi-arid regions. The climate is an influential factor when the amount of organic matter in the soil is concerned. In some regions, organic matter increases with an increase in rainfall, and in some, organic matter decreases with an increase in the temperature. In regions receiving uniform rainfall and vegetation, the content of organic matter content has been found to increase two to three times for every 10oC fall in the temperature. In mean annual temperatures, the organic matter content in surface soils increases as we pass from arid to per-humid regions in India.

Organic Matter Varies With The Depth Of Soil

Organic matter is usually more in surface layers and gradually decreases as you go under the surface. Generally, plant residues, manures, and other organic wastes are incorporated into the surface layer. This is the main reason for the higher content of organic matter on the soil surface. Soils that have a cover of vegetation like grasslands and forest soils contain a greater amount of organic matter than arable soils.

Organic Matter Varies With Soil Texture And Cultivation

Soils that have a light or coarse texture, usually contain less organic matter than heavy or fine-textured soils. The high moisture content of clay soils is responsible for greater vegetative growth and slow decomposition. Hence, clay soils are richer in organic matter than coarse or sandy soils. Poorly drained soils are richer in organic matter than well-drained soils. Soils that are regularly plowed or harrowed contain less organic matter than those which are not frequently cultivated. Due to regular cultivation, the decomposition process becomes faster and more aeration leads to depletion of humus in the soil. Hence, uncultivated soils higher accumulation of organic matter.

Organic Matter In Soil

Both internal and external factors that leave behind high quantities of crop residues in the soil, lead to their slow decomposition, high precipitation, low temperature, high moisture status, poor aeration, acid reaction, and heavy soil texture, allow greater accumulation of humus in the soil. These factors also favor the synthesis of microbial cell substances which in return increases the humus content. On the other hand, low precipitation, high temperature, low moisture content, high aeration, neutral or alkaline reactions, and light open texture lead to quick decomposition of humus and reduce the amount of organic matter in the soil.

Reference:
  • Dr. J.A. Daji, Dr. J.R. Kadam and Dr. N.D. Patil, Text Book fo SOIL SCIENCE,1996, p232-236.
  • (a) Ind. J. Agric. Sci., 1946, 16, 316.
  • (a) V.S. Abhyakar; M.Sc. (Agri.) Thesis, Univ. Bombay.

VIJAYKUMAR M. SARUR
M.Sc. Agro-chemical and Pest Management
Chief-Agronomist
Kothari Agritech Pvt. Ltd.
Mob. 9545552988