Faidherbia

Faidherbia is a tree which has a special nitrogen-fixing property and an unusual habit known as "reverse leaf phenology".

Unlike other trees, Faidherbia sheds its leaves and goes dormant during the early rainy season.

Its leaves grow again only in the dry season. This means that it is extremely compatible with food crops because it does not compete with them for water, nutrients or light.

According to the Agroforestry Centre, farmers in Malawi testify the tree is like a "fertilizer factory in the field", as it takes nitrogen from the air, fixes it in the leaves and subsequently incorporates it into the soil.

The Agroforestry Centre's research showed that in Malawi maize yields increased by 280 per cent in the zone under the tree canopy compared with the zone outside the tree canopy. In Zambia, unfertilized maize yields in the vicinity of Faidherbia trees averaged 4.1 tonnes per hectare, compared to 1.3 tonnes nearby but beyond the tree canopy.

Maize is the staple food for many African countries, but when grown as a mono-crop over many years it drains the soil of vital nutrients.

On average, maize yields on the 27 million hectares on which it is grown in Africa are one tenth the equivalent of American yields. One of the reasons is limited use of fertilizers, but the Faidherbia tree - pending some further research on its impact on the water table - may now provide a natural and widespread fertilizer fix.

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