Paying farmers in Sub-Saharan Africa to sequester carbon may provide a stronger incentive to improve soil quality than simply offering official fertiliser subsidies, a modelling study has found.
In recent years, fertiliser subsidies have been vigorously promoted to farmers in countries like Ghana, Kenya, Malawi, Tanzania and Zambia. But despite widespread levels of soil degradation, take-up rates of subsidised fertilisers have been low.
To look at ways of incentivising farmers to increase their use of soil improvement technologies, researchers investigated soil improvement practices at nine sites in Kenya, Malawi and Uganda where maize, rice or sorghum were grown.
Techniques included using crop residue alone, and various combinations of crop residue, nitrogen fertiliser and manure.
The researchers found that all five techniques resulted in higher crop yields. Writing in Agricultural Systems (26 May) they also found that each method improved carbon sequestration, and suggest that this might provide an opportunity for extra external support through such agencies such as the Clean Development Mechanism in the form of "payments for environmental services".
Working on the basis of total potential profit over a 30-year period, they found that payments for carbon sequestration would be equally or more profitable than subsidised fertiliser schemes.
Paswel Marenya, the study's lead author and a postdoctoral fellow at the US-based International Food Policy Research Institute, said: "If you could get the market to buy agricultural carbon for US$4 per tonne, then you could transfer significant resources to farmers at levels that are comparable to what would have happened if you gave them... fertiliser subsidies."
Zwide Jere, managing director of Total LandCare in Malawi, an NGO that aims to improve the livelihoods of smallholder famers, said African governments should regard fertiliser subsidies as a short-term strategy and encouraged them to explore and promote other incentives for agroforestry and conservation agriculture.
But Rita Laker-Ojok, executive director of AT Uganda Ltd, a provider of agricultural extension services based in Kampala, said monitoring the soil management techniques of millions of farmers is a daunting logistical challenge.
She told SciDev.Net that a carbon credit programme in Uganda had failed, despite "many years" of seeking a way to pay dairy farmers for reducing the methane emissions of their cows through an improved diet.
"Despite a lot of effort and investment, we could not get a methodology approved that would satisfy the licensing authorities," said Laker-Ojok, adding that it would be even harder to track sales of manure for soil fertility management.