Newsportal - Ruhr-Universität Bochum
The magic of biochar
Ensuring a steady food supply is a problem in many regions of Africa – and the strong population growth will only exacerbate it in the future. Yet the agricultural sector could definitely produce greater yields. The key lies in improving soil quality. This is the research focus of Isaac Asirifi, PhD student at the Department of Soil Science and Soil Ecology at Ruhr-Universität Bochum (RUB). He shows that a mixture of biochar and ash can increase the yield of a cultivated area by a quarter when applied a single time. The report has been published in Rubin, the RUB’s science magazine.
To find out how to improve soil quality, Isaac Asirifi focused on three vegetation zones in Ghana and took soil samples there: in the coastal savannah in the south-east of the country, in the mixed deciduous forest in the heartland, and in the Guinea savannah in the north, where it rains only once a year. The studies have shown that one problem in particular stands in the way of high-yield harvests: the pH level is much too low and impedes the settlement of beneficial microorganisms.
The potential of harvest residues
There is a way to make it easier for them: biochar. “In Ghana, plant residues that can’t be eaten or fed to livestock aren’t used after harvesting, but are simply burned,” says Asirifi. This also creates the problem that a lot of carbon dioxide is released into the atmosphere, which fuels climate change. But there is great potential in the crop residues: if they are burnt in containers in the absence of oxygen, biochar is produced. It can be made from anything left over from the harvest, and no complex or expensive technology is needed. “If it is introduced into the top 15 to 25 centimetres of the soil, it works its magic,” explains Asirifi. That means: once applied, it improves soil quality for years to come.
Delivering a quarter more yield
The charcoal ensures that microorganisms such as bacteria and fungi can settle and thrive more easily. “It reduces acidity, and the many small cavities in the biochar provide protection from predators.” In addition, it doesn’t wash out. A welcome side effect is that the carbon contained in the biochar remains bound in the soil and is not released into the atmosphere as is the case with open burning.
By mixing 0.5 to one per cent ash into the biochar and spreading the mixture on the fields, ten to 15 tonnes per hectare of land will suffice. Farmland treated in this way yields about a quarter more than an untreated one.
Soil Science and Soil Ecology
Institute of Geography
Phone: +49 234 32 23322
28 September 2021