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Senegal: A scruffy shrub gets new respect for contributions to soil fertility (NPR)

For years, the instructions were clear—farmers should rip out Guiera senegalensis shrubs, clearing their fields before the planting season. The humble, hardy, leafy bursts of green—known as n’guer in the local Wolof language, somehow thrive in Senegal’s semi-arid climate, popping up knee-high out of the sandy soil. It was assumed that they must be competing with crops for water.

But now, there’s a new attitude among a small but growing contingent of farmers and researchers: Keep the shrubs. Prune them, trim them down to ground level, plant your crops around them and even right over them—the deep roots of the shrubs won’t mind.

The advice goes even further: Plant more shrubs in your fields, about one every three square feet.

Sidy Diakhate has seen the power of the shrubs. He’s an agricultural consultant and a farmer. His six-acre farm sits on the flat, sandy plains of Khombole, about 60 miles east of the rapidly expanding capital, Dakar.

His fields are covered with the hardy shrubs. And they’re the reason, he says, that his plots of peppers, eggplant, and cabbage have grown so well this season.

Guiera senegalensis is a tough plant that has been growing here for thousands of years, like its sister shrub, Piliostigma reticulatum, known as kafalataku in the local Dioula language. The second shrub is similar but thrives in Senegal’s wetter south. When farmers plant their crops during the rainy season in the Sahel’s sandy plains, the shrubs create “fertility islands” by locking in topsoil and cooling the surroundings. They also bring water to the surface from deep underground beyond other crops’ natural reach through a process called hydraulic lift. At night, when photosynthesis stops, excess water drawn up to the surface from the shrubs’ deep roots leaks out, nourishing the soil near the surface.

Also, the leaves and branches of these shrubs, if pruned, shredded, and spread on the ground, provide fertilizing biomass. 

Ibrahima Diedhiou is a professor at the University of Thiès who has been studying these shrubs for two decades, and now collaborates with American scientists. He says that farmers face serious challenges like soil degradation, climate change, and especially drought. 

He adds: “Farmers can use [these shrubs] to reduce their vulnerability to food insecurity, because the shrubs can improve crop yields, protect the soil, and reduce vulnerability to drought, which is the big challenge in our local context.”

After years of study, people like Mr. Diedhiou and Mr. Diakhate—who earned his Ph.D. studying how the shrubs can act as natural pesticides by keeping nematodes at bay—are now trying to move their research out of the classroom and into the hands of farmers.

In late 2021, shrub enthusiasts, farmers, and students gathered for a field day organized by the Agro-Shrub Alliance and the University of Thies. In the testing fields, the attendees were invited to look at millet grown in shrub-filled fields. The stalks towered over much smaller stands of millet grown apart from the shrubs. Experimental millet plots incorporating shrubs had 105% and 128% higher yields when planted with kafalataku and n’guer, respectively. Using the shrubs also eliminates the need for expensive and environmentally-costly fertilizer.

The Agro-Shrub Alliance is currently scaling up the reach of this shrub intercropping method, known as the “Optimized Shrub System” across Senegal. The shrubs only need to be planted in the fields once. Beyond that, they require pruning, maintenance to chop the leaves and stems for biomass, and protection from grazing animals. Mr. Diedhiou notes that all this represents added labour for farmers. 

Specialized mulching machines were presented at the field day to help mulch the leaves and stems of the shrubs, but this equipment is not widely available. And farmers need to be guided by agricultural extension agents through the first year as their shrub seedlings mature and they learn how to incorporate the plants into their farms. All this requires concerted political will, as well as time, effort, and funding.

Amanda Davey is the CEO of the Agro-Shrub Alliance, a non-profit spun off from Ohio State University’s research on the shrubs. She believes that this low-cost practice is key to increasing farmers’ resiliency and ability to adapt to climate change. She says that, even if farmers can’t manage shrubs on all of their farmland, they could at least do so on one plot. She says, “I see this as a kind of insurance. If you can’t do all 10 hectares, you do one hectare, and you get food for your family.”

For now, Mr. Diakhate says his neighbours have been inquisitively examining his vegetable fields. He says, “They are very curious.” A few have asked him if they can use the method themselves, and he’s keen to bring them on board. He says that this curiosity, combined with government support, is what it’s going to take to get more people to adopt these practices and overcome barriers such as increased labour. 

He says, “I think we can try to build a new future using this type of shrub.”

This story is based on an article written by Nick Roll and published by NPR’s Goats and Soda in February 2022, titled “Farmers in Senegal learn to respect a scruffy shrub that gets no respect.” To read the full story, go to: https://www.npr.org/sections/goatsandsoda/2022/02/20/1079777745/farmers-in-senegal-learn-to-respect-a-scruffy-shrub-that-gets-no-respect [1]