Unique Tree To Boost Farming In Nigeria, Others

By: Michael Simire on August 27th, 2009

Help may soon be on offer to farmers in Nigeria and other African nations if research announced in Nairobi, Kenya, this week by a team of scientists lives up to its initial promise.

They disclosed  at the 2nd World Congress of Agroforestry (WAC2) that a type of acacia tree with a growth habit different from other trees holds particular promise as a free and unlimited source of nitrogen for soils. Nitrogen is essential to healthy plant life.

With its nitrogen-fixing qualities, the tall, long-leaved acacia tree (or <em>Faidherbia albida</em>), said the scientists, could limit the use of chemical fertilisers.

It can also provide fodder for livestock, wood for construction and fuel wood, medicine through its bark, and windbreaks and erosion control to farmers across sub-Saharan Africa.

The tree illustrates the benefits of growing trees on farms and is said to be adapted to a wide array of climates and soils from the deserts to the humid tropics.

“The future of trees is on farms,” said Dr Dennis Garrity, Director General of the World Agroforestry Centre (ICRAF), one of 15 centres supported by the Consultative Group on International Agricultural Research (CGIAR).

The centre is hosting the Congress, which has convened about 800 global experts to discuss the importance of growing trees on farms for humanity’s survival.

“Growing the right tree in the right place on farms in sub-Saharan Africa – and worldwide – has the potential to slow climate change, feed more people, and protect the environment. This tree, as a source of free, organic nitrogen, is an example of that. There are many other examples of solutions to African farming that exist here already”, said Dr Garrity.

African farmland is severely degraded and African farmers, on average, apply only 10 percent of the soil nutrients used in the rest of the world, said the scientists. They said low-cost options are critical to reversing the continent’s declining farm productivity, even as sharply increasing fertiliser prices further limit the choices African farmers have to improve yields while protecting forests from further clearing.

The <em>Faidherbia acacia</em> has the quality of “reverse leaf phenology,” which drives the tree to go dormant and shed its nitrogen-rich leaves during the early rainy season – when seeds are being planted and need the nitrogen – and then to re-grow its leaves when the dry season begins and crops are dormant.

This makes it highly compatible with food crops, because it does not compete with them for light – only the bare branches of the tree’s canopy spread overhead while crops grow to maturity.

The leaves and pods provide a crucial source of fodder in the dry season for livestock when other plants have dried up.

Research on the trees began over 60 years ago when scientists observed that farmers throughout the Sahelian region of Africa were retaining them in their sorghum and millet fields.

They are a frequent component of farming systems in Senegal, Mali, Burkina Faso, Niger, Chad, Sudan, and Ethiopia, and in parts of northern Ghana, northern Nigeria, and northern Cameroon.

The tree is grown on over 4.8 million hectares of land in Niger. Half a million farmers in Malawi and in the southern highlands of Tanzania grow it on their maize fields.

In Malawi, maize yields increased by up to 280 percent in the zone under the tree canopy compared with the zone outside it. In Zambia, recent unpublished observations showed that unfertilised maize yields in the vicinity of the <em>Faidherbia</em> trees averaged 4.1 tonnes per hectare, compared to 1.3 tonnes nearby, but beyond the tree canopy.

Yield increases have also been documented in unfertilised millets grown under the trees in West Africa, in sorghum in Ethiopia and other parts of Africa, and in India, and also in groundnuts and cotton.

Often millet and sorghum exhibit no further response to artificial fertilisers beyond that provided by the tree’s leaf fall.

Currently, the Departments of Agriculture in both Malawi and Zambia are seeking to double maize production with the use of the tree. They recommend that farmers establish 100 Faidherbia trees on each hectare of maize that is planted.

“Knowledge of this tree is farmer-driven,” said Dr Garrity. “We are now combining the scientific knowledge base with the farmer knowledge base.

“There is sufficient research on both sides to warrant dramatically scaling-up the planting of this tree on farms across Africa through extension programmes. The risks to farmers are low; it requires very little labour, and delivers many benefits.

“Thus far we have failed to do enough to refine, adapt and extend the unique properties of these trees to the more than 50 million food crop farmers who desperately need home-grown solutions to their food production problems,” he added.