role of earthworm in soil fertility

Earthworm

1. Role of Earthworms in soil fertility Tejaswini . Uppuluri UG13AGR1758

2. I ntroduction Organisms living in the soil and their biological activity play an important role in the soil and their productivity. Among soil organisms, earthworm role is significant. The activities of earthworm like power of communication, translocation, burrowing and mechanical blending enhance aeration, nutrient and water holding capacity of a soil. But in contrary reduction in bulk density is a negative consequence leading to soil erosion. Earthworms in nature promote infilteration of water in ground as they make soil porous and promote drainage.

3. Role of eaRTHWORMS IN SOIL Earthworms bring up the nutrients from deep in the soil and deposit them on the soil surface as castings, hence counteract leaching of nutrients. Earthworms contribute to soil fertility by improving soil structure , mixing and tilling the soil, increasing humus formation and increasing the available plant nutrients. Earthworms eat a large amount of litter but only a small fraction of digested material (5-10%) is assimilated by the earthworms and the rest are excreted out in the form of earthworm cast which are rich in NPK , micronutrients and beneficial soil microbes .

4. Role of eaRTHWORMS IN SOIL Bacteria in the earthworm gut destroy harmful chemicals ingested by worms and also break down organic wastes . Auxin is a plant growth regulator produced in earthworm castings that stimulate roots to grow faster and deeper . Nitrogen fixation in casts is comparatively higher than in soil due to presence of nitrogen fixing bacteria in the earthworm gut and also in earthworm casts. Nitrogenase activity in casts is also higher thus contributing to higher nitrogen fixation in casts than surrounding soil.

5. Benefits of earthworms Water infilteration Soil aeration Soil compaction and soil tilth Soil organic matter Plant available nutrients Nematode control Soil pH Beneficial microbes

6. Influence of earthworm on soil Effect of earthworms on soil quality i . Effects on physical properties of soil ii. Effect on chemical properties of soil a. Earthworm and soil nitrogen b. Earthworm and soil phosphorus iii. Earthworms and microorganisms Earthworms and plant growth Earthworms and organic solid waste management Earthworms and land reclamation

7. Effect on physical properties The earthworm's burrowing creates a multitude of channels through the soil Maintaining the soil structure . Enabling processes of aeration and drainage. The earthworm not only creates passages for air and water to traverse the soil . Modifies the vital organic component that makes a soil healthy. Earthworms promote the formation of nutrient-rich casts (globules of soil, stable in soil [mucus]) High soil aggregation and soil fertility and quality .

8. Eefect on biological property In many soils, earthworms play a major role in the conversion of large pieces of organic matter into rich humus, thus improving soil fertility . Once in the burrow, the worm will shred the leaf and partially digest it and mingle it with the earth . Worm casts (see bottom right) can contain 40 percent more humus than the top of soil in which the worm is living. Most of the species of microorganisms that occur in the alimentary canal of earthworms are the same as those in the soils in which the earthworms live.

9. Effect on biological property The microbial population in earthworm casts is greatly increased compared with the surrounding soil . Earthworm casts usually have a greater population of fungi, actinomycetes and bacteria and higher enzyme activity than the surrounding soil. Microbial activity in earthworm casts may have an important effect on Soil crumb structure by increasing the stability of the worm-cast-soil relative to that of the surrounding soil. Earthworms are very important in inoculating soils with microorganisms. Many microorganisms in the soil are in a dormant stage with low metabolic activity, awaiting suitable conditions like the earthworm or mucus to become active . Earthworms have been shown to increase the overall microbial respiration in soil , thereby enhancing microbial degradation of organic matter.

10. effect on chemical property Earthworms bring about mineralisation of organic matter and thereby release the nutrients in available forms that can be taken up by the plants. Organic matter that passes through the earthworm gut is egested in their casts, which is broken down into much finer particles, so that a greater surface area of the organic matter is exposed to microbial decomposition. Earthworms have major influences on the nutrient cycling process in many ecosystems. Earthworms contribute nutrients in the form of nitrogenous wastes. Their casts have higher base-exchangeable bases , phosphorus, exchangeable potassium and manganese and total exchangeable calcium.

11. effect on chemical property Earthworms favour nitrification since they increase bacterial population and soil aeration. The most important effect of earthworms may be the stimulation of microbial activity in casts that enhances the transformation of soluble nitrogen into microbial protein thereby preventing their loss through leaching to the lower horizons of the soil. C: N ratios of casts are lower than that of the surrounding soil The influence of earthworms on soil nitrogen and nitrogen cycling. The nitrogenous products of earthworm metabolism are returned to the soil through casts, urine, mucoproteins and dead tissues of earthworms.

12. Table 1:Effects of vermicompost and NPK on physical parameters in post harvest soils of black gram T 1 - Control ( without application of inorganic fertilizer or manure) T 2 - Recommended dose of NPK (50:25:0 kgha -1 ) T 3 - Recommended dose of vermicompost (5 t ha -1 ) T 4 - A pplication of 50% vermicompost + 50% NPK

13. Physical parameters Clay loam soil CD values Sandy loam soil CD values T 1 T 2 T 3 T 4 T 1 T 2 T 3 T 4 Pore space (%) 35.40 34.20 39.60 37.96 5.27* 32.51 31.80 36.54 33.72 5.58* Particle density ( Mgm -3 ) 1.69 1.76 1.28 1.42 0.04 NS 1.68 1.66 1.87 1.82 0.03 NS Bulk density ( Mgm -3 ) 1.13 1.16 0.91 1.02 0.16* 1.24 1.25 0.98 1.10 0.14* WHC(%) 72.94 72.80 95.62 90.40 1.59* 59.20 58.41 77.46 70.30 1.67* CEC (C.mol kg -1 ) 24.30 23.84 28.36 27.80 0.26* 23.20 22.73 27.92 26.48 0.28* Values of mean of six observations, *significant at 0.05% level NS- not significant

14. Conclusion Earthworms are an important part of the soil ecosystem. They help improve soil structure and soil chemical and biological properties. They are especially important in no-till, helping to stimulate air and water movement in soil. Earthworms tend to thrive most without tillage, if sufficient crop residue is left on the soil surface. Crop rotations, cover crops, manure , fertilizer and lime applications all affect earthworm populations. Some pesticides, especially organophosphates and carbamates , are toxic to earthworms . Most herbicides do not pose a threat to earthworms.

15. REFERENCES: Vermicomposting and vermiwash - L.L.Somani Vermi-bitechnology - L.S.Ranganathan https://www.hindawi.com.journals www.ijat-aatsea.com

16. Thank you