A study conducted by the PUR Lab, in partnership with the UNA University from Honduras, shows that cocoa agroforestry systems can increase soil macro-biodiversity by four times.
What is soil macro-biodiversity?
Soil organisms (beetles, spring-tails, mites, worm, spiders, ants, nematodes, fungi, bacteria, etc.) are essential to soil fertility and plants growth. They step in determinant phenomenon for soil fertility: nutrient cycling, decomposition of organic matter, soil structuring, carbon sequestration and regulation of greenhouse gas emissions.
Soil biodiversity is very sensitive to crop management: utilization of fungicides, pesticides, soil tillage, mono-cropping and intensive fertilization affect soil biodiversity and its ecological functionalities. A dead soil is an unproductive soil!
“Soil’s host a quarter of our planet biodiversity” (FAO, 2014). It is one of the world’s most complex and diversified ecosystem.
How do we measure soil macro-biodiversity?
Since early 2015, we are working with a local university in Honduras (Universidad Nacional de Agricultura) and cocoa farmers involved in the reforestation project. We use an ISO normalized method (ISO 23611-5:2011): the Tropical Soil Biology and Fertility (TSBF) method.
– We extract a 19 cm3 soil cube in each sample spot, with 5 repetitions per studied plot.
– We identify and count the different macro-organisms. The key figures are the number of individuals and the diversity of species.
– The sampling is repeated on different land uses: full sun, agroforestry, reforested area and secondary forest. Then we can assess the effects of land use on macro-organisms’ population.
Three species of soil macro-organisms were studied (Scolopendra, Phyllophaga and Lumbricus). They are key players for:
– Organic matter decomposition (Lumbricus and Phyllophaga);
– Predation on potential pest species (Scolopendra and Phyllophaga);
– Soil structuring (Lumbricus).
Our study shows that there are almost 4 times more Scolopendra, Phyllophaga and Lumbricus in agroforestry and reforested systems than in full sun system.