Skip to main content

How Can African Farms Get Better Soil?

Two new studies look at how to improve soil quality and improve Africa’s food security.

By Nathan Collins


A worker toils as sugar cane waste slow burns, part of the process in making biochar, at the Eco Fuel Africa factory in Lugazi on January 29, 2013. (Photo: Michele Sibiloni/AFP/Getty Images)

Africa is not a great place to farm. Indeed, more than half the continent is unsuitable “for any kind of agriculture except nomadic grazing,” according to a 1997 study, and it’s a big problem for food security in the region. Now, two recentstudies are taking on that problem—with one looking hundreds of years into the past for ways to improve Africa’s future.

“In African dryland landscapes, improving nutrient-poor soils is important for increasing agricultural productivity, particularly because a significant population growth is expected in this region over the next 100 years,” write Tatsuki Ogura, a researcher at the RIKEN Center for Sustainable Resource Science, and colleagues in Scientific Reports.

Their approach to the problem is based on a substance called biochar, a carbon-rich, charcoal-like substance produced when burning plants and other organic material in the absence of oxygen. The stuff is, however, controversial: Despite claims it could improve crop yields (and trap greenhouse gases and produce electricity during its production), a 2011 review found mixed results at best.

“God made the soil, but we put the dirt there and made it fertile.”

Hoping to improve on past results, Ogura and colleagues studied torrified biochar, which is produced at somewhat lower temperatures than other forms. After mixing a low-quality soil called aridisol typical of arid African countries with about 5 percent torrified biochar, the team found the soil held about 5 percent more water and contained more readily available nutrients, such as potassium, sodium, and phosphorous. Plants grown in the the enriched soil were generally a bit shorter but also had thicker stems and longer roots and were slightly heavier that those grown in plain aridisol.

In contrast to that relatively modern approach, Dawit Solomon and colleagues took inspiration from Amazonian Dark Earth, a rich soil that was produced in pre-Columbian South America—though no one knows whether is was produced deliberately or as an unintentional byproduct of the region’s earliest settlements. After finding similar soil in Ghana and Liberia, which they dubbed African Dark Earth (AfDE) Solomon and team wanted to find out where it came from—so they asked around.

As it turned out, the locals in Ghana and Liberia knew exactly where the stuff came from: they made it. Specifically, they took all manner of cooking and agricultural waste—ash, bones, palm thatch, even the byproducts of homemade soap—and just tossed it in with the rest of the soil. According to one local the team interviewed, “God made the soil, but we put the dirt there and made it fertile.” Another interviewee pointed out that if you dug down deep enough, you could find where the AfDE ended and ordinary soil began, “and this shows how old the town is.”

(Incidentally, the researchers did that analysis and found that AfDE had been present for between 100 and nearly 700 years in the towns and villages they searched.)

The findings, the researchers write in Frontiers in Ecology and the Environment, could prompt “a climate-smart foundation for agricultural innovation with [Sub-Saharan African] farming practices in ways that could improve sustainable production.”