Role of charcoal addition on infiltration processes and soil water content characteristics of a candy loam soil

Terra preta (TP) is a soil amendment which is enriched with powdered charcoal, with nutrient sources from organic residues, and that constitutes a resource to improve soils for sustainable land use systems (Glaser, 2007). Terra preta-dark soil is inspired by the highly successful historic practice of soil building in the Amazon and other parts of the world. This work involves a relatively unexplored topic: the comprehension of infiltration processes and soil water content characteristics in a sandy loam soil combined with different fractions of terra preta amendments. This analysis contributes to a better understanding of the relationship between fractions of charcoal in terms of terra preta content and soil water holding capacity. First, a physical and hydraulic characterization was performed on soil samples with different charcoal content. Then, they were exposed to a rain simulation experiment under controlled conditions. A descriptive statistical analysis was applied for a quantitative evaluation of the results. It was found that as the fraction of terra preta increased, infiltration and percolation rates decreased, but water holding capacity increased. This can influence water ponding at the surface, leading to runoff formation. However, the effect on water holding capacity is an opportunity, integrated to other sustainable practices, to overcome drought effects and reduce the need for irrigation.