Prof. (Dr) R.D. Gupta
Although the earthworms appear to be humble yet they are very active organisms. They perform a numerous beneficial activities in nature. As a matter of fact, the earthworms perhaps cover a number of important aspects towards agriculture ,especially organic farming. In the first place , the borrowing activity of the earthworms brings about soil tillage. Although in most conventional forms of tillage implements, it is possible to plough the soil upto about 30 cm depth ,while the earthworms can do this up to 3 m or even more without adversely affecting plants in any manner. Besides, the earthworms feed on soil organic matter thus breakdown its various particles and finally turn them into humus.
Humus in turn helps in Improving the physical and chemical properties. Usually the soil horizons having earthworms show a granular to subangular blocky structure. There is significant improvement of water stable aggregates. Improve water holding capacity, cation exchange capacity and the plant nutrients content of the soils. The improvement is generally more in topsoil ( 0 to 15 cm depth).
Generally ,with increase in number of earthworms, the bulk density is reduced while the total pore space and water holding capacity is increased significantly both in surface and subsurface soils. Humic substances like humic acid, fulvic acid, humin etc. have various uses. Firstly ,they serve storehouse of plant nutrients both macro and micro. Moreover, they regulate the ionic exchange phenomenon like clay minerals, which is of much economic importance in agriculture and other sectors after photosynthesis. Humic substances also serve as chelating agents which are responsible to render the availability of micronutrients slowly and uniformly.
In conventional composting of animal dung, its full conversion is done in approximately 6 months. However, through earthworms i.e. 10 Kg worms(1000 in number ) would convert, 1tonneanimal dung per month with five square meters, composting pits.
In totality, earthworms casts production bring about highly beneficial form of soil tillage with several amendments like addition of plant nutrients. It has been found that soils with earthworms cast have more nutrients i.e.5 times more nitrogen , 7 times phosphorus and 11 times potassium, 2 times magnesium and calcium.
Of various roles of earthworms , benefits accrue even after their death under natural conditions. Nitrogen content in the soil is increased with decay of dead earthworms. It has been estimated that in earthworm dead species, individually can yield up to 10- 12 mg of nitrate. A population of 3.75 million ha-1even after death earthworms would yield approximately 220-230 kg of NO3-N ha-1. Earthworms have another important role in maintenance of C: N and C:P ratios essential for the release of nutrients to plants and the microorganisms.
(The writer is Ex-Associate Dean Cum Chief Scientist KVK Jammu, SKUAST-J)