A new type of agriculture practice could restore the beleaguered soils of Africa and help the continent feed itself in the coming decades, soil scientists say. Writing in Nature, Washington State University researcher John Reganold and colleagues say a system of \"perenniation,\" which mixes food crops with trees and perennial plants that live for two years or more, can lead to increased yields and sustainability. Thousands of farmers are already practicing variations of perenniation, reducing the need for artificial inputs while improving soil, and in some cases dramatically increasing yields, a WSU release reported Wednesday. One-fourth of the world\'s undernourished population lives in sub-Saharan Africa, where nutrient-poor soils have yields that are one-tenth of the U.S. Midwest, the researchers said. \"Of the various factors needing urgent attention to increase agricultural productivity, scientists from the region have identified soil quality as a top priority,\" the researchers wrote. Perenniation research should be supported at the same level as research into mineral fertilizers and seed development, they wrote while acknowledging such research could run to tens of millions of dollars. \"Yet such numbers pale in comparison to the losses of nitrogen, phosphorous and potassium from sub-Saharan farm fields each year,\" the researchers said, saying the losses are the equivalent of billions of dollars of fertilizer.