SOMETIMES low tech is much better than no tech. A simple, affordable way to apply crop fertiliser directly to plants looks set to revolutionise the way poor farmers in sub-Saharan Africa grow food. And it all hinges on beer bottle tops.
This week, African heads of state meet in Abuja, Nigeria, for a summit on the continent’s deepening soil fertility crisis. Three-quarters of the soil in sub-Saharan Africa is severely depleted of nutrients, because farmers do not use fertiliser or spread manure.
The summit aims to hatch a soil rescue plan, and this is where the beer-bottle tops may well play an unexpected role. They make ideal measuring pots for “micro-dosing”, a technique that lets farmers focus precious nutrients where they are needed rather than wasting them. The results so far are encouraging.
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“Tops make ideal pots for measuring out nutrients where they are needed”
Having pinpointed a lack of nitrates as the main factor limiting yields in southern Africa, Steve Twomlow of the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), based in Bulawayo, Zimbabwe, established that about 5 grams of ammonium nitrate is enough to feed three plants: that’s one beer cap full. Conventional scattering of fertiliser uses five capfuls for every three plants.
For sorghum and pearl millet, Twomlow found that dabbing the fertiliser dose around the base of a plant once it is knee-high boosts yields by between 30 and 50 per cent. “Nearly every treated farm in our trials gave positive yield increases,” says Twomlow.
In parallel trials in western Africa, where lack of phosphates was the limiting factor, the problem could be corrected by giving each plant a “three-finger pinch” containing 2 grams of diammonium phosphate, plus a gram or so of urea.
Here yields for pearl millet and sorghum rose by up to 120 per cent, boosting farmers’ incomes by up to 134 per cent.
For micro-dosing to work, though, ICRISAT is pressing agribusinesses to make fertiliser available in smaller, more affordable packets. This is expected to be another focus of the Abuja summit.
