1In Madagascar in 2017, researchers showed that the addition of earthworms to soil could increase the yield of a rain-fed rice field by 40%. Hence the invertebrates’ nickname of “soil engineers” used in the 1990s during the launch of a research programme on soil macrofauna.

Earthworm castings in a field, Togo.

2At the time, the scientific community was just beginning to realise that invertebrates visible to the naked eye (earthworms, termites and larvae) play a leading role in the functioning of soil. They facilitate organic matter decomposition and nutrient recycling and availability to plants. By building underground networks, they also alter the physical properties (soil structure, water retention, erosion) and biological properties (modification of microbial activity) of soil. Furthermore, they can improve plant resistance to certain pathogens such as rice blast and certain parasitic nematodes.

••• Earthworms, insect larvae and termites have a major effect on soil properties •••

3IRD has largely contributed to the highlighting and quantifying in tropical countries of these remarkable properties, notably via indicators making use of the macrofauna’s activity to describe soil functions and understand the condition of an eco- or agro-system. These functional indicators have been the subject of extensive research and developments over the past few years, including the introduction of the Biofunctool^® tool in 2018, which provides a set of field indicators to measure soil health.

Use of compost for agricultural work, Madagascar.

4Meanwhile IRD researchers, at the forefront of this issue, tested protocols to intensify certain macrofauna functions, thereby increasing the productivity and sustainability of small family farms.

“The study of soil macrofauna and its functions in agriculture and the environment is a scientific aspect which has only been addressed in Madagascar since the partnership between IRD (Eco&Sols UMR) and the Radioisotope laboratory was launched in 2004. Since then, it has been found that these organisms, more specifically earthworms, play a major role in maintaining the sustainability of Madagascar’s agrosystems. The results of the studies carried out suggest that the direct introduction of earthworms, by inoculating parcels, or their indirect introduction, via the use of vermicomposting, contributes to the sustainability of Madagascar’s agrosystems.”
Professor Tantely Razafimbelo, Radioisotope Laboratory (LRI), Madagascar