Organic matter in the soil

Farmers in all ages have used the colour of a soil to assist in judging its productivity: the darker the soil the more оrganic matter content and the more desirable it was for crop production. Even today, dark-coloured soils are usually considered more productive than light-coloured ones. Under composed organic matter aids in crop production by active physically to provide a coat of protection against heat and cold and against the effect of beating raindrops.

No one can deny that plants can be grown successful without organic matter. But everyone will agree that the most efficient way to grow plants is in a productive soil rich in fresh, decomposing organic matter.

Organic matter has many functions in the soils. Some of the essential nutrients for plants growth come directly from organic matter. Where it is insufficient, artificial fertilizers must be used to supplement it. Organic material contributes chemical constituents to soil water largely in the form of acid products. These chemicals perform several function but perhaps the most important is to break down some of the minerals of the parent rock, making them available to plant

Organic matter is an important factor in the water capacity and rate of absorption of some soils. Often droughty soil are greatly improved by generous addition of organic matte Tight soils with poor air circulation show marked improvement when organic matter is added. This is particularly important in the early stages of plant growth, at the time seed germination and early root development. Soil when they dry out after rains; therefore, the young tender plants have little difficulty in breaking through the surface. In cultivated soils organic matter is an important factor of tillage. Not only does it contribute to the ease of cultivation, but it also reduces the delay of tillage after rains.

Organic matter reduces soil erosion. This is of particular significance where abundant undecomposed material remains on the surface and where plant roots form a tangled mass in the A horizon. Decomposed organic matter, or humus, also tends to bind together soil mineral particles, induce water absorption, check the rate of water runoff, and reduce the re­moval of surface soil particles by wind. Proper management and control of organic matter is one of the best means of preventing both water and wind erosion.

For any given soil in any given location, the organic matter content fluctuates between relatively narrow limits. Thus if a farmed soil contains 3 per cent organic matter under normal management, this can be reduced to possibly 2 1/2 per cent by poor management, and it can be raised to possib­ly 3 1/2 percent by good management. The amount of organic matter in any soil tends to fluctuate over a range of about 1 per cent. Only by exceptional measures, such as annual ap­plications of large amounts of manure, can this soil's content of organic matter be raised above 3 1/2 per cent, and only by very drastic means, such as excessive cultivation without the use of animal manures or green manures, can it be reduced below the 2 1/2 per cent level.

Date: 2015-10-19; view: 905; Нарушение авторских прав