The recent G8 meeting in in Italy unveiled a plan to commit $US 20 billion over three years to funding the development of agriculture to tackle persistent food shortages particularly in Africa.

One of the most promising areas of reserch is the use of "fertilser trees". These are varieties of shrubs that capture nitrogen from the air and transfer it to the soil – restoring nutrients and potentially doubling or trebling harvests.

According to Jeffrey Sachs, director of the UN Millennium Project, "fertiliser trees" are among the most promising means for achieving the goal of halving global hunger by 2015.

A major project to evaluate the use of fertiliser tress was begun in Malawi and other southern African countries in 2007. Some 200,000 farmers in Malawi are involved in the project.

Four different systems are being tested:

  • The first system is sequential planting of nitrogen-fixing trees with maize, shortening the amount of time land needs to lie fallow;
  • In the second system, nitrogen-fixing shrubs are planted along with maize and heavily pruned during maize growth to prevent competition.
  • The third system involves planting nitrogen-fixing trees a few weeks after maize to reduce competition between the plants.
  • In the fourth system, the leaves of the trees are used as fertiliser for vegetable crop production in the wetlands and maize production in the uplands.

Maize yields have averaged 3.7 tonnes per hectare compared to 1 tonne per hectare in plots without fertilizer trees or mineral fertilizer.

The downside of using fertiser trees is that there is a generally a greater labour investment in establishing, maintaining, and pruning back the leaves and other biomass of the trees compared to conventional maize production.

(Based on sources including ScDevNet and Science Alert)