Ecosystem services for West African farming families: the role of woody shrub mulch

1 Introduction Woody vegetation in semi-arid West Africa provides ecosystem services that benefit local livelihoods through provision and regulation of natural resources (Sinare and Gordon, 2015). Use of traditional fallows to restore soil productive capacity via organic matter accruement has been compromised by population growth in West Africa and increased land degradation (Bonetti and Jouve, 1999). Continued crop cultivation and insufficient fallow periods have thus, led to severe soil organic matter depletion and subsequent soil degradation in semi-arid West Africa. This situation ultimately undermines food provision of local farm communities and may affect irreversibly ecosystem provision and regulation services within these landscapes. Improved use of local manure and compost as options to regenerate soils may be limited by availability (usually in homestead enclosures), transport constraints (dependent on donkey cart access and distance to fields), and labour requirements (harvest and application effort). As crop residues are vastly collected for livestock forage during the dry season, farming families in certain dryland areas are left with little sources of organic matter to regenerate soils. Innovative farmers in Burkina Faso have developed spatial and temporal shrub-crop arrangements by switching from a strategy of slash-and-burn to a strategy of slash-and-mulch to optimize services provided by in situ native woody shrub biomass (Félix, 2015). Increasingly, scientific evidence supports key roles that shrub vegetation types have in sustaining crop productivity and enhancing soil quality in the sub-region (Dossa et al., 2013; Hernandez et al., 2015; Lahmar et al., 2012; Yélémou et al., 2013). Event though woody shrub-based farming systems may have heterogeneous shrub densities, these provide soil water regulation services (Kizito et al., 2007) and nutrient provision services through organic matter from branches and leaves (Ba et al., 2014). In this context, if 100% available woody shrub biomass is the usual application by farmers as mulch, then two questions arise: (1) To what extent is crop productivity affected by in situ available mulch application? and (2) What is the effect of twice that dose of application on crop productivity?