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Faidherbia – Africa’s fertiliser factory

Posted by Lindy on January 11, 2010


http://www.new-ag.info//developments/devItem.php?a=1036

The nitrogen-fixing acacia tree, Faidherbia albida, boosts soil fertility
credit: Georgina Smith

Malawi largest and entirely unintended export is its top soil, evidence of which is seen in the deep scars formed by gully erosion and the silt-filled river channels.

The loss of soil fertility and consequent crop failure has a devastating effect on the poor subsistence farmers of the area.

They are being trained to change their ways, improve their land and their standard of living. The idea is to minimise soil disturbance while raising soil quality. This is achieved by:

Planting the nitrogen-fixing acacia tree every 10 rows

Dig out small planting puts, a minimum till technique that disturbs only 10% of the soil

Put compost /fertilizer in the base and alternate crops between maize one time and groundnuts (which also fix oxygen) the next time

Leave plant residues on the surface to protect the soil instead of burning them

The acacia keeps its leaves in the dry season which gives the crops protection but drops these nitrogen rich leaves in the wet, which is equivalent 300kg  fertilizer per hectare. Research in Malawi and Zambia shows that mature trees can sustain unfertilised maize yields of 2.5 to 4 tons per hectare – 200 to 400 per cent more than national averages.

Head of outreach services at the Zambia National Farmers Union, Hamusimbi Coillard, comments: “When someone is confronted with food insecurity, they need something immediate. This is not an instant thing.” However in Zambia, more than 150,000 farmers have begun to practise conservation agriculture, which is now embedded in national policy.

Meanwhile, at the World Agroforestry Centre in Nairobi, director general Dennis Garrity is excited about the carbon sequestration potential of planting Faidherbia trees, in addition to the soil fertility benefits. “This is no panacea,” he says, “but if this vision was applied on 50 million hectares of crop land, think of the carbon sequestration opportunities in Africa.”

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