Due to the predicted impacts of climate change, many farmers are increasingly concerned about severe soil compaction and water stagnation on their fields. To prevent the deterioration of arable soils, appropriate soil management stratigies have to be developed. Earthworms are an important component of the soil biodiversity and their positive effects on soil structure are well-known. A variety of functional groups of earthworms can be restored through decrease in a soil disturbance and occurence of crop residues in the upper

soil. Investigating earthworm biomass and population is a very complex process and therefore consists of various methods of sampling. However, it is difficult to conduct efficient investigations due to horizontally aggregated earthworm populations and their complex phenologies. Of the vaiorus methods, hand sorting which involves sorting through soil samples by hand is one of the most earliest popular sampling methods. The soil washing method is more effective in sorting out cocoons and smaller earthworms. This method consists of a combination of washing and sieving soil samples, with a possible flotation stage. Another method that is used for soil sampling is the electrical method which consists of inserting an electrode into the groud causing earthworms to surface due to the electrical pulse in the soil. These methods, however, usually result in disrupting earthworm biomass and population, killing and injuring them and affecting their habitats. Considering the relationships between heavy metals and earthworms inhabiting in contaminated soils, it needs to adjust study focus on the long-term effects of multiple elements, not one heavy metal, to earthworms. However, these methods make it difficult to consistantly study and investigate a selective biomass during long periods.

With future developements in terms of remote sensing used for detecting the small — or large-scale acquisition of information of an object or phenomenon, these issues will no longer serve as a problem because biomass can be studied without any need of disruption. Although underground remote sensing technologies are in use, they have not yet been applied to the investigation of living organisms, such as earthworms. For that reason, we believe that scientists and remote sensing developers should put their heads together to optimize remote sensing equipment to the investigation of underground living organisms. These advancements will significantly help researchers to consistantly study a select biomass and calculate the amount of toxic materials that are being inserted into the soil more accurately.

2. Conclusion

The long-term applications of organic waste materials containing heavy metals and HEMs affected the establishment of Megascolecid and Moniligastrid earthworms in field. The biomass of earthworms in lysimeter and microcosm soil tests would provide valuable tools for establishing the integrated hazard assessment system for organic wastes. Future research is needed to establish additional soil physico-chemical characteristics, particularly those that might influence heavy-metal bioaccumulation and bioavailability and physical habitat such as compaction and soil water holding capacity across treatment through time course.

3. Acknowledgement

This work was supported by the Rural Development Administration and WCU (World Class University) programme (R31-10056) through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology.