Recycling and Priming Action of Organic Matter

After reading this article you will learn about the recycling and priming action of organic matter.

Recycling of Organic Matter:

Generally crop residues should be left on or returned to the soil. This guideline takes advantage of the benefits of organic matter in soil, its aggregation of soil particles, improvement of aeration status, infiltration and permeability of soil, its reservoir of plant nutrients and energy for micro-organisms etc.

Such major benefits of organic residues are derived only if the material is somewhat easily and rapidly decomposing, a condition that exists only if fresh organic residues are incorporated into the soil regularly. These rapidly decomposing organic materials can be recognised as “active organic matter”.

If only the humus residues (decompose very slowly) are left the release of different nutrient elements is slow. Slower decomposing organic matter produces a much less amount of gums or polysaccharides (long chain sugars), which can bind the soil particles forming aggregates and subsequently improves soil structure.

If the supply of organic materials to the soil stops, polysaccharides like substances continue to decompose and within a very short period structural improvement of soil can be lost. Thus, new supplies of fresh organic waste materials must be continuously available to maintain the production of polysaccharide substances as well as to provide additional plant nutrients.

Conservation tillage (fewer tillage operations and less disturbance of plant residues) is an another economic practice for recycling of organic residues as well as for maintenance of organic matter in the soil. Because it provides less opportunity for mixing organic residues with the soil and as a result the soil organic matter remains in large amounts than where sufficient tillage operation is done.

Priming Action of Organic Matter:

Newly applied plant residues can either stimulate or retard decomposition of native soil organic- matter. This change in decomposition rate is described as “priming” and is usually positive. The priming action is defined as the loss of native soil organic matter through the application of fresh organic residues in the soil.

From the figure 19.8 it is found that the amount of native C lost through “priming” was taken as the differences between the amount of soil CO₂ evolved in the presence and absence of fresh organic residues.

The loss of native soil organic matter due to priming action may be attributed that there is a building of a large and vigorous population of micro-organisms when energy material (fresh organic materials) is applied to the soil and that these micro-organisms subsequently produce enzymes which attack the native soil organic matter.

The extent of organic matter loss will depend upon various factors like size and activity of soil micro-organisms. Easily decomposable plant residues like young succulent plant tissues would be particularly effective in increasing the loss of native soil organic matter.