Effects of soil faunal activity and woody shrubs on water infiltration rates in a semi-arid fallow of Senegal

The effects of soil faunal activity on the physical properties of the soils of a 2-year-old fallow in the sahelian zone of Senegal were studied. Facto rs studied included the presence or absence of woody shrubs and the effect of protection of plots from grazing and removal of fuel wood. The experimen tal design included a control in which termite activity was excluded by tre ating the soil with the persistent insecticide dieldrin. In both the protected and unprotected area of the experiment, termite burro wing activity (as measured by the number of entrance holes per square-metre ) and water infiltration rates were significantly (ca. 80%) lower in termit e exclusion plots than in plots not treated with insecticide 2 years after initial treatment. In protected plots where termites were present, there wa s a significant increase in infiltration rates in the part where woody shru bs were removed. In unprotected plots, by contrast, the presence of shrubs significantly increased infiltration rates, whether or not termites were pr esent. Burrowing activity of earthworms was greater in the protected than in the u nprotected area, and in the unprotected area burrowing in dieldrin treated plots was significantly increased by almost 65%. Activity of ants appeared to be little affected by the different treatments. The results demonstrate that the presence of healthy soil faunal populations was important in the i nfiltration of water in fallow soils and that protection from grazing and h uman activity improves faunal activity and water infiltration. (C) 2001 Els evier Science B.V. All rights reserved.