Termite and earthworm abundance and taxonomic richness under long-term conservation soil management in Saria, Burkina Faso, West Africa

Unsustainable crop and soil management practices are major causes of soil degradation and declining soil biodiversity in West Africa. Identifying soil management practices that favor macrofauna abundance is highly desirable for long-term soil health. This study investigates the effects of long-term conservation soil management on termite and earthworm abundance and taxonomic richness in the central plateau of Burkina Faso. Trials included rotations with 5Mgha⁻¹yr⁻² of organic matter added (established in 1960), application of 10Mgha⁻¹yr⁻¹applied with additional organic (manure or straw) and mineral inputs (established in 1980) and different tillage systems (established in 1990) where 10Mgha⁻¹yr⁻¹ of organic matter was also applied. Soil macrofauna was surveyed at the soil surface and in the upper 30cm using transect and monolith sampling methods, eight weeks after sorghum crop planting. A total of five termite taxa: Trinervitermes sp., Microtermes sp., Odontotermes magdalenae, Macrotermes sp. and Amitermes stephensoni; belonging to the family of Termitidae, and two earthworm taxa: Dichogaster affinis, Millsonia inermis; from the family of Acanthodrilidae were found. Termite taxonomic richness per treatment ranged between 1 and 4, while earthworm taxa ranged from 0 to 2. Under rotation, one termite taxa and no earthworm taxa were identified. In the organic amendment plots, three termite and two earthworm taxa were found. And light tillage (animal or hand) resulted in four termite taxa and one earthworm taxa. The two types of fauna clearly responded differently to the different conservation soil management practices. Under rotation lower recorded macrofauna population was attributed to the lower rate of applied organic matter compared to levels applied in the organic amendment and tillage trials and where more macrofauna were found. Location of food stock (rooting depth of different crops in the rotation) also had a significant effect on termite presence. Effect of rooting depth on earthworms was not observable due to the absence of earthworms in the rotation trials (possibly due to insecticide application. Manure treatments favored earthworms, while sorghum straw treatments favored termites likely due to respective preference for easy versus difficult to digest organic sources. Animal plowing and hand hoeing had similar and significantly positive effects and both termite and earthworm biological components compared to tractor tillage. We conclude that termite and earthworm abundance and taxonomic richness are most significantly affected by the type and amount of organic matter applied and tillage regimes, with rooting depth of rotations crops also playing a significant role. To promote macrofauna abundance and taxonomic richness in soils, integrated conservation soil management practices with attention to the particular needs and preferences of termites and earthworms is needed.