Senegal farmers now keep Guiera shrubs in fields, and millet yields doubled in trials

Under French rule from at least the 1950s into the 1970s, Senegalese farmers were told to uproot Guiera senegalensis shrubs, on the logic that they compete with crops for water. Many still burn them before planting. Researchers from the University of Thiès and Ohio State University now say they should stay.

The shrubs lift water through hydraulic redistribution: at night deep roots leak water into the surface soil. They also create 'fertility islands' by holding topsoil, and pruned branches spread as mulch fertilize the field. Because the plants are native and kept trimmed, they do not block simple horse- or donkey-drawn plows. Researchers suggest about one shrub per three square feet.

The Agro-Shrub Alliance, a nonprofit spun out of OSU research, is working to scale what researchers call the Optimized Shrub System across Senegal.

Keep the native shrub, prune it and plant crops around it, because its deep roots help the crop rather than compete.

Deep-rooted shrubs reach water that crops can't.

Pruned shrub leaves and stems feed the soil without bought fertilizer.

They fit smallholder tools and cost little.

Similar regreening has worked elsewhere in the Sahel.

A long-assumed pest can be an asset, and testing the assumption can turn a removal rule into a cheap, local fix.

OSU researcher Richard Dick told NPR in 2022 that experimental millet plots grown with the shrubs saw 105% and 128% yield increases with P. reticulatum and G. senegalensis respectively. Scaling will be hard: the shrubs need protection from grazing animals and regular pruning, mulching machines are scarce, and farmers need extension support for the first year. Evidence is from research plots.