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How a once-maligned shrub can help farmers in Senegal grow better crops

A field of millet crops grow in Senegal, enhanced by the presence of Guiera senegalensis A field of millet crops grow in Senegal, enhanced by the presence of Guiera senegalensis Matthew Bright
11 Jan
2019
Once dismissed as undesirable competitors, certain West African shrubs are now being recognised as significant crop enhancers

Imagine a miracle plant that could increase the yield of crops such as millet and sorghum by as much as 900 per cent when planted alongside them, producing thick, prosperous heads of grain, as opposed to mere tufts of vegetation. Remarkably, such a plant appears to exist, although it is only beginning to attract widespread attention. 

In Senegal, Richard Dick, a soil scientist at Ohio State University, observed that millet crops that were disproportionately prosperous in challenging, arid conditions were often found growing side-by-side with a ubiquitous woody shrub that few people had previously paid much attention to – except to recommend they be removed. ‘We found literature from the 1950s recommending farmers remove the shrubs from cropped fields in West Africa,’ says Dick, ‘and my Senegalese colleagues reported that this was the message from the national extension agencies in Senegal up through the 1970s. The assumption was that these would compete with crops for water and nutrients.’

Weed cultivation during growing season with ShrubWeed cultivation takes place during the millet growing season in Senegal (Image: Richard Dick)

Instead, new research now suggests that these shrubs, especially one named Guiera senegalensis, are capable of retaining stores of water even in drought conditions, stretching their roots several metres underground, then sharing this water with surrounding plants in a process known as ‘bioirrigation’. Benefits for neighbour plants appear to include better soil quality, greater nutrient uptake and improved water use efficiency. ‘The farmers likely have never thought of trying to increase shrub densities, because by and large they do not know how to get new plants established,’ says Dick. 

GS summer regrowth milletMillet (the taller leafy plant) grows successfully alongside Guiera senegalensis (Image: Matthew Bright)

While not yet officially promoted, these shrubs have been identified as potential assets in combating poverty and famine in highly drought-prone regions (such as the infamously tough Sahel) via a mechanism Dick and colleagues are developing known as the optimized shrub-intercropping system (OSS). ‘We need to have a group of farmers successfully adapt and manage OSS and from there, they can become advocates for the system,’ he says. They have also started a non-profit organisation – the Agro-Shrub Alliance (agroshrub.org) – dedicated to ‘promoting shrub based farming through on-farm research and technical training with smallholder farming families across the West African Sahel’.  

This was published in the January 2019  edition of Geographical magazine

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