This article is part of our special report Food and nutrition security.
SPECIAL REPORT / Every year the world loses roughly 24 billion tonnes of fertile soil, with chemical fertilisers singled out as one of the main culprits. Yet, agriculture experts are calling for more widespread use of the substances to improve land fertility and boost yields.
Fertile land is a basic necessity for mankind as it provides the nutrients for crops on which its survival depends.
Still, more than 24 billion tonnes of the Earth's soil is lost every year, due mainly to erosion, over-grazing, pollution and natural disasters.
At this year’s Global Soil Week in Berlin, researchers called for a reorientation in agriculture policy to preserve or improve land fertility. The issue is particularly acute in Africa, where governments and international aid agencies are pushing to increase agricultural productivity, without destroying the environment.
"In sub-Saharan Africa the main problems are soil erosion and the loss of soil fertility due to unsustainable land use," explains Rolf Sommer, an agriculture economist who works for the International Center for Tropical Agriculture (CIAT) in Nairobi, Kenya.
In Europe, the slow take-up of organic agriculture has helped maintain the nutrient content of soil. To earn their organic label, farmers here are only allowed to fertilise land with natural ingredients such as cow dung, liquid manure, mulch or straw.
But according to Sommer, such organic solutions are currently unfeasible in Sub-Saharan Africa, where soils are relatively infertile and lack sufficient nutrients. In this region, farmers are forced to use chemical fertilising methods in order to produce any crops at all, he says.
"Organic fertiliser must be produced somehow, before it can be used," Sommer points out. "Moderate use of mineral fertilisers is the only possibility at the moment."
WWF claims chemical fertilisers accelerate climate change
Conservation groups like the World Wide Fund for Nature (WWF) beg to differ, criticising the use of chemical fertilisers.
"Mineral fertilisers in agriculture indicate the finite state of natural resources. They endanger tomorrow's food security," says a WWF study conducted in cooperation with the German foundation Heinrich-Böll-Stiftung.
The effects of chemical-synthetic fertilisers include decomposition of humus soil, loss of biodiversity, soil acidification and nitrous oxide emissions, which are a burden for the environment and accelerate climate change, the study argues.
In addition, the poorest of the population have no direct access to raw materials used to produce their fertilisers. "Farmers are threatened by dependence on large fertiliser producers," said Birgit Wilhelm of the WWF. For this reason, she supports organic cultivation in Africa and investing money in parallel training measures, rather than on chemical fertilisers.
"We could completely convert our agriculture to organic. Not only would this be environmentally friendly, it would also be economically sustainable," said Mwatima Juma of the Tanzania Organic Agriculture Movement (TOAM), an NGO.
"Research findings show organic fertilisation leads to higher productivity in the long-term," she contends.
Push to invest in fertiliser market
This is not the view of most African governments, who have been pushing for a massive increase in the use of mineral fertilisers in recent years.
In 2007, the African Development Bank created the African Fertiliser Financing Mechanism, which offers millions in donations to produce and distribute fertilisers. The motive is clear: mineral fertilisers promise additional revenues for farmers in the short-term, thereby promoting economic growth.
But Juma says governments deliberately support research in plant varieties that can only survive with mineral fertilisation. "This leads to the impression that chemical fertilisation is the only solution," said Juma, who fears that subsidies for the fertilisation market might encourage corruption.
With her pro-organic position, Juma was in a minority at the Global Soil Week, where a majority of participants underlined the need to keep a balanced mix of organic and chemical fertilisers. To satisfy a growing demand for food, farmers must produce much more in the coming years, many experts pointed out, arguing that such an increase would be impossible without the use of mineral fertilisers.
"There are numerous sustainable plans for the intensification of agriculture in Africa. This is where African states and international donors should invest. It is already happening, but more is needed," said Sommer.
Doing nothing will be costly
What is more, many smallholders in Africa have little understanding of the nutrient content of their soil, Sommer pointed out. As a result, they are not in a position to decide on the fertilisation method that is best suited to their needs. To help them, researchers should generate region-specific fertilisation recommendations with the help of infrared spectroscopy, Sommer said.
"In the best case scenario, agricultural advisors would have a small instrument on hand, with which they could scan the soil and be able to directly inform farmers of deficiencies and how to increase yields through cost-effective and environmentally friendly means," Sommer said. But without the necessary political will at every level, it would not work, he warned.
"To put an end to soil erosion, other plans are needed. For example, financial incentives could encourage investment in soil preservation measures like terracing of steep hillsides or the reforestation of these surfaces. As a whole, this will cost society less, because doing nothing will end up being costly."