Ramial wood amendments (Piliostigma reticulatum) mitigate degradation of tropical soils but do not replenish nutrient exports

Restoring degraded soils to support food production is a major challenge for WestAfrican smallholders who have developed local innovations to counter furtherdegradation. The objective of this study was to evaluate a local farmer's technique thatuses ramial wood (RW) as soil amendment (Piliostigma reticulatum shrub). Three treat-ments were applied in an experimental plot in Burkina Faso: control (no amendment),low RW (3 Mg fresh mass·ha−1·yr−1), and high RW (12 Mg fresh mass·ha−1·yr−1). RWwas chipped to <5‐cm pieces and either buried or mulched. Topsoil carbon (C), nitrogen(N), and phosphorus (P) in control and low‐RW treatments declined after 7 years ofcontinuous sorghum cultivation. Use of high‐RW amendment stabilized soil C contentwhile N and P declined, thus not replenishing nutrient exports. Net contribution to soilC in the layer measuring 0–15 cm was 15% of the applied C in the high‐RWamendments. Although biomass and grain yields were higher in high‐RW treatments,crop productivity declined throughout the experiment for all treatments. Termite castson RW treatments evidenced the potential role of wood‐foraging termites in dilutingthe impact of RW on soil fertility build‐up and soil water content. We conclude thatmitigating soil degradation under semiarid conditions in Burkina Faso would requirelarge amounts of woody amendments, particularly if the level of termite activity is high.Additional nutrient sources would be needed to compensate for removal in exportedproducts so that biomass and grain production can be stabilized or increased.