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

Abstract

Restoring degraded soils to support food production is a major challenge for West African smallholders who have developed local innovations to counter further degradation. The objective of this study was to evaluate a local farmer's technique that uses ramial wood (RW) as soil amendment (Piliostigma reticulatum shrub). Three treatments 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). RW was 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 of continuous sorghum cultivation. Use of high‐RW amendment stabilized soil C content while N and P declined, thus not replenishing nutrient exports. Net contribution to soil C in the layer measuring 0–15 cm was 15% of the applied C in the high‐RW amendments. Although biomass and grain yields were higher in high‐RW treatments, crop productivity declined throughout the experiment for all treatments. Termite casts on RW treatments evidenced the potential role of wood‐foraging termites in diluting the impact of RW on soil fertility build‐up and soil water content. We conclude that mitigating soil degradation under semiarid conditions in Burkina Faso would require large amounts of woody amendments, particularly if the level of termite activity is high. Additional nutrient sources would be needed to compensate for removal in exported products so that biomass and grain production can be stabilized or increased.

Enhancing agroecosystem productivity with woody perennials in semi-arid West Africa. A meta-analysis

“…No homogenised term for ramial wood amendment practice exists. As a consequence, across the literature, the following terms were identified as being similar or closely related to ramial wood amendments:Agroforestry mulches (Tilander and Bonzi 1997)Prunings (Bayala et al 2003)Leaf mulch (Bayala et al 2005)Woody perennial leaf biomass (Yélémou et al 2014)Woody biomass (Gruenewald et al 2007; Debela et al 2011)Wood shavings (Chiroma et al 2006; Gajalakshmi and Abbasi 2008)Wood waste (Bulmer et al 2007; Andry et al 2011)Woody debris (Brown and Naeth 2014)Wood (Bonanomi et al 2014)Native agroforestry plant residues (Iyamuremye et al 2000)Native shrub residues (Dossa et al 2009)Branches of indigenous shrub (Wezel and Böcker 1999)Shrub material (Chapuis-Lardy et al 2015)Ramial chipped wood (Gómez 1997; Robert et al 2014)Ramial wood amendments (Barthès et al 2015; Félix et al 2018)Chopped twig wood (Aman et al 1996) Rameaux ligneux (Kabré 2010) Bois raméal (Barthès et al 2010) Bois raméal fragmenté (Zongo 2009; Ba et al 2014; Somé 2014)…”

“…Ramial wood (RW) amendment availability relies on existing tree and shrub vegetation. The mechanisms by which woody amendments may provide benefits to soils and crops remain poorly understood, and no effective agronomic recommendations on the use of leaf and branch material currently exist in the SWA context (Bayala et al 2003; Barthès et al 2015; Félix et al 2018).…”

40. Ethical issues involving long-term land leases: a soil sciences perspective

“…Soil conservation involves costs and the advantages of investing in soil restoration may take some years to result in improved or stabilized yields. In Burkina Faso, for example, where lands are relatively poor, adding 12 t ha -1 of woody biomass will allow the maintenance of soil carbon in time, yet these amounts are four times as high as the available biomass in the surrounding landscapes (3 t ha -1 ), which are not enough to counter soil carbon losses (Félix et al, 2018). Through the integration of woody shrub perennials and other smart-uses of biodiversity (e.g.…”

Restoration and rehabilitation of degraded land in arid and semiarid environments: Editorial

“…Importantly, the practice of using locally sourced amendments can also contribute to the circular economy reducing the amount of exogenous fertilizers and contributing to climate change mitigation (Hueso-González et al, 2018). In socioeconomically developing regions, organic amendments such as native mulches can be in fact one of the few available options for improving soil fertility as dicssued in this issue by Félix et al (2018) and Ndegwa, Nehren, Anhuf, and Iiyama (2018). Félix et al (2018) show that adding a native shrub, for example, ramial wood, in high volumes could sustain crop yields in Burkina Faso.…”

“…In socioeconomically developing regions, organic amendments such as native mulches can be in fact one of the few available options for improving soil fertility as dicssued in this issue by Félix et al (2018) and Ndegwa, Nehren, Anhuf, and Iiyama (2018). Félix et al (2018) show that adding a native shrub, for example, ramial wood, in high volumes could sustain crop yields in Burkina Faso. Yet, the amount of biomass needed exceeds the available capacity in the landscape and afforestation would be needed to support food production.…”