**3. Earthworms and microorganisms**

There is a complex inter-relationship between earthworms and microorganisms. 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. The microbial population in earthworm casts is greatly increased compared with the surrounding soil (Haynes, *et al.,* 1999). Earthworm casts usually have a greater population of fungi, actinomycetes and bacteria and higher enzyme activity than the surrounding soil (Lachnicht and Hendrix, 2001). 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 (Edwards and Bohlen, 1996). 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 gut (Lachnicht and Hendrix, 2001) or mucus (Lavelle *et al.,* 1983) to become active. Earthworms have been shown to increase the overall microbial respiration in soil, thereby enhancing microbial degradation of organic matter.

#### **4. Earthworms and plant growth**

Earthworms prepare the ground in an excellent manner for the growth of plants (Darwin, 1881). Darwin's findings that earthworms play a beneficial role in soil fertility that is important for plant growth have been acknowledged by many workers (Lee and Foster, 1991; Alban and Berry, 1994; Nooren *et al.,* 1995; Decaens *et al.,* 1999). Earthworms have beneficial effects on soil and many workers have attempted to demonstrate that these effects increase plant growth and yields of crops (Decaens *et al.,* 1999; Lalitha *et al.,* 2000;). Earthworms release substances beneficial to plant growth like auxins and cytokinins (Krishnamoorthy and Vajranabhaiah, 1986). The beneficial effect of earthworms on plant growth may be due to several reasons apart from the presence of macronutrients and micronutrients in vermicast and in their secretions in considerable quantities (Lalitha *et al.,* 2000; Ismail, 2005). Reports suggest that certain metabolites produced by earthworms may be responsible for stimulating plant growth.

#### **5. Earthworms and land reclamation**

The success of land reclamation by conventional techniques is often limited by poor soil structure and low inherent soil fertility, and even in productive soils, a marked deterioration in the botanical composition of the sward can occur within a number of years (Hoogerkamp *et al.,* 1983). A number of studies indicate that earthworms play an important part in

manganese and total exchangeable calcium. 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 (Bouché, 1983). Lee (1983) summarised the influence of earthworms on soil nitrogen and nitrogen cycling. According to him, nitrogenous products of earthworm metabolism are returned to the soil through casts, urine, mucoproteins and dead tissues of

There is a complex inter-relationship between earthworms and microorganisms. 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. The microbial population in earthworm casts is greatly increased compared with the surrounding soil (Haynes, *et al.,* 1999). Earthworm casts usually have a greater population of fungi, actinomycetes and bacteria and higher enzyme activity than the surrounding soil (Lachnicht and Hendrix, 2001). 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 (Edwards and Bohlen, 1996). 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 gut (Lachnicht and Hendrix, 2001) or mucus (Lavelle *et al.,* 1983) to become active. Earthworms have been shown to increase the overall microbial

Earthworms prepare the ground in an excellent manner for the growth of plants (Darwin, 1881). Darwin's findings that earthworms play a beneficial role in soil fertility that is important for plant growth have been acknowledged by many workers (Lee and Foster, 1991; Alban and Berry, 1994; Nooren *et al.,* 1995; Decaens *et al.,* 1999). Earthworms have beneficial effects on soil and many workers have attempted to demonstrate that these effects increase plant growth and yields of crops (Decaens *et al.,* 1999; Lalitha *et al.,* 2000;). Earthworms release substances beneficial to plant growth like auxins and cytokinins (Krishnamoorthy and Vajranabhaiah, 1986). The beneficial effect of earthworms on plant growth may be due to several reasons apart from the presence of macronutrients and micronutrients in vermicast and in their secretions in considerable quantities (Lalitha *et al.,* 2000; Ismail, 2005). Reports suggest that certain

metabolites produced by earthworms may be responsible for stimulating plant growth.

The success of land reclamation by conventional techniques is often limited by poor soil structure and low inherent soil fertility, and even in productive soils, a marked deterioration in the botanical composition of the sward can occur within a number of years (Hoogerkamp *et al.,* 1983). A number of studies indicate that earthworms play an important part in

respiration in soil, thereby enhancing microbial degradation of organic matter.

earthworms.

**3. Earthworms and microorganisms** 

**4. Earthworms and plant growth** 

**5. Earthworms and land reclamation** 

improving reclaimed soils (Boyle *et al.,* 1997; Butt, 1999). Some experiments on improving impoverished soils by stimulating earthworm populations have been reported (Butt *et al.,* 1997). A successful introduction of earthworms in reclaimable soil could be achieved by overcoming factors like unfavorable moisture conditions, excessive fluctuation of surface temperature and lack of suitable food (Satchell, 1983).
