Agroforestry Trees Improve Water Infiltrability in Semi-arid Tropical Parklands in Burkina Faso

Maintaining appropriate levels of soil infiltrability is important for avoiding undesirable levels of surface runoff and erosion and for maintaining adequate rates of soil and groundwater recharge. This study was conducted with the aim of investigating the effects of Faidherbia albida (apple-ring acacia) and Vitellaria paradoxa (shea butter tree) trees and additions of inorganic fertilizer, leaves and compost on soil infiltrability in two agroforestry parkland systems in the western part of Burkina Faso. Infiltrability was measured before tilling both under and outside canopies of these trees, using tension disc and double-ring infiltrometers. The results show that infiltrability was 33% higher on average under than outside canopies in both agroforestry parkland systems. The compost, leaves and inorganic fertilizer did not improve infiltrability significantly during the study period. More than 75% of the infiltrability estimates obtained using ring infiltrometers outside the canopies were lower than 40 mm/h. In contrast, less than 10% of those obtained from under canopies were lower than this. This could have highly significant effects on run-off, erosion and recharge since rain intensity measurements collected over three years at 30 min intervals showed that up to 35% of the annual precipitation fell with intensities ≥ 40 mm/h. The study demonstrates the potential of improving infiltrability and reducing surface runoff by managing trees appropriately in agroforestry systems in semi-arid tropics.