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2. Southern Africa: Tree is a ‘fertilizer factory in the field’ (Mongabay, UNEP)

Many years ago, scientists noticed something interesting happening in Malawian fields. Tall, thorny trees grew in the middle of sorghum and millet plots. The scientists wanted to know why farmers kept these trees. What was their secret? What the scientists would discover could help farmers in other parts of Africa double or triple their yields.

The tree is called Faidherbia albida. In Swahili, it is called Mgunga. In Bambara, it is Balanzan. Faidherbia is a type of acacia tree with special properties. It fixes nitrogen in the soil – an important nutrient for many crops.
Dennis Garrity is director general of the World Agroforestry Centre, or ICRAF. He notes that farmers have driven the knowledge of this special tree. Now, ICRAF is combining farmer knowledge with scientific research to better understand and promote Faidherbia.

The benefits of Faidherbia have been studied in Malawi and Zambia. In each country, scientists measured maize yields in plots where Faidherbia was planted. They compared this to maize yields in plots without Faidherbia. In both countries, yields of maize planted near Faidherbia were double or triple the yields of maize without the tree.
It’s no wonder that Malawian farmers call Faidherbia a “fertilizer factory in the field.”

Mr. Garrity explains how the tree adds nitrogen to the soil. Early in the rainy season, Faidherbia becomes dormant. Its nitrogen-rich leaves fall to the ground. This happens at the same time that farmers plant their seeds. The seedlings soak up nutrients from the fallen leaves.

Another advantage is that, since the tree is dormant during the rainy season, it does not compete with crops for sunlight or nutrients.

The Departments of Agriculture in Malawi and Zambia have taken note of this research. They are recommending that farmers plant one hundred Faidherbia trees on every hectare of maize.