Reganold said that poor soil may have resulted from years of weathering that leaches many of the nutrients. But in some cases farmers may have done more harm than good.

“They have been actually using farming practices where they’re not putting in organic matter. They’re not putting in fertilizers. They can’t afford those things. And it just runs the soil down more. So they’re actually mining the soil. So they’re worsening the situation,” he said.

He said that the major nutrients that farmland needs are nitrogen, phosphorous and potassium.

“The big one,” he said, “is nitrogen. That’s the nutrient that the plant demands the most and that’s the fertilizer that’s mostly needed.”

He estimated that up to two billion dollars worth of nitrogen, phosphorous and potassium is lost from African soil each year.

That’s where perenniation comes in. It adds nutrients back into the soil.

“We came up with the term perenniation, but the systems have been around for a while. We use the term perenniation. It defines three systems that are already used in Africa. The oldest of the three is called evergreen agriculture and it’s where farmers actually plant trees with their crops. And they’ve been doing this to the best of my knowledge for 60 years, but it’s starting to gain ground,” he said.