Wonder tree nourishes soil, boosts yields

By Ally Jamah

Farmers are missing out on the benefits of a unique acacia tree that significantly boosts soil fertility and crop yields yet it grows naturally.

Experts say the unique acacia tree — Faidherbia albida — or mgunga in Kiswahili, reduces farmers’ dependence on expensive fertilisers and boosts food production by up to three times. "We have evidence of doubled and tripled yields for small scale farmers without increase in labour or the need to apply nitrogen fertilsers," says Dennis Garrity Director General of the World Agroforestry Centre in Nairobi. The organisation is lobbying for the "wonder tree" to be planted countrywide.

"It acts like a fertiliser factory. You get this rich leaf that is a great organic fertiliser for free," he says

Garrily was speaking at the recent second World Congress on Agroforestry held in Nairobi’, which brought together about 800 experts to discuss how to help farmers plant more trees.

Dr Geoffrey Kironchi from the University of Nairobi says only a few farmers are aware of its existence and benefits. "Although it grows naturally, especially the arid north the tree has not been promoted to the farmers in Kenya despite its enormous benefits," he says.

Water retention

Studies in Zambia found that the species can provide nutrients equivalent to 300kg of nitrogen and 3kg of phosphorous a hectare per year, and increase soil water retention by up to 40 per cent within a growing season.

"In West Africa the tree has increased not only sorghum yield by 2.5 times, but also the content of proteins in the grain by 3.4 times for a crop that was grown under the canopy of the compared to that what was grown in the adjacent open space," he says.

Most farmers cannot afford the expensive fertilisers on the market. "Soil fertility is one of the major constraints to food production in sub-Saharan Africa, and nitrogen is one of the most limiting elements," says Garrity.

The tree has a special nitrogen-fixing property that highly enriches the soil, the same way organic and inorganic fertilisers do.

Agriculture is regularly thrown into crisis, whenever fertiliser prices shoot up like it did last year. The Government was forced to import and sell fertilisers to farmers at subsidised prizes, but the programme has since collapsed.

According to the centre maize yields increased by 280 per cent in the zone under the tree canopy in Malawi compared to those outside.

The Malawi government has started an aggressive campaign to popularise the tree, recommending farmers to plant at least 100 Faidherbia trees on each hectare of maize that is planted.

Yield increases have also been documented in unfertilised millets in West Africa, for sorghum in Ethiopia, other parts of Africa, and in India, in addition to groundnuts and cotton.