What’s the verdict on chemical fertilisers?

Tuesday, 30 July 2013 09:05 GMT

Farmers redeem vouchers for fertiliser in Nigeria, August 2010. PHOTO/IFDC

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Chemical fertilisers are often cast as the villain for their contribution to farm emissions, but they can help fight hunger

The giant neem tree that grows at the southeastern corner of Yorwataafaa’s house in Bompari village has seen its share of negotiations. Yorwataafaa is the chief of Bompari, in the Upper West region of Ghana, and his tree serves as the meeting place for all community business. Its umbrella-like branches are the only effective respite from the brutal sun, creating a sanctuary for thought, discussion and decision.

When talking about climate-smart agriculture - practices that improve food security and adaptation to climate change while being mindful of mitigation - chemical or synthetic fertilisers are often cast as the villain for their contribution to agricultural emissions.

Ongoing research from the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) is taking a look at options for fertiliser application and putting them to the test. Just how climate-smart are they from the farmers’ perspective, and what might be preventing their adoption in places like Bompari village?

Yorwataafaa, seated on the most well-worn of the log benches under the meeting tree, has no shortage of opinions on the subject. “Members of this community know that manure helps improve soil fertility, but then, not everyone has animals,” he says. “For many, this means that they have no choice but to rely on the chemical fertilisers.” These chemicals come with another challenge, however: the cost and difficulty of acquiring them.

Rates of fertiliser use in Ghana rank among the lowest in sub-Saharan Africa, a region that is already the lowest consumer of fertiliser in the world, according to Ghana’s Ministry of Food and Agriculture. Recent state subsidy programmes have attempted to improve the situation, but their results have been mixed.

As for last year’s subsidy programme, “by the time we heard that there was fertiliser available, it was too late in the season to make good use of it,” says Yorwataafaa. “Then again, not every farmer had access to a subsidy coupon, and some farmers could not afford the fertiliser even at the subsidized rates. You can practically say that no one in this community took advantage of the subsidy.”


Nutrients such as nitrogen, phosphate and potassium are essential to boost crop yields, but when supplied through chemical fertiliser the bigger harvests come at the cost of high CO2 emissions from production and transport and increased N2O release from agricultural soils.

In fact, 32 percent of direct agricultural emissions come from soils, a large part from fertiliser use. If we are looking to make agriculture more climate-smart, should we really be interested in using chemical fertilisers at all, much less increasing their use?

The verdict on the climate-smart status of chemical fertilisers is highly dependent on the context of its use: are we talking fertiliser-overloaded Southeast Asia, or nutrient-starved Africa? What happens when deforestation, land degradation, hunger and poverty are added to the mix?  

Production scenarios from researchers at Columbia University reveal that where population is dense and land is scarce, intensification with fertilisers may be the only way to meet basic food security goals while still resulting in net mitigation. This scenario is possible when the carbon storage potential of forested lands that remain intact by avoiding agricultural expansion outweighs the extra nitrogen emissions from increased fertiliser use.

This conclusion relies on several assumptions: that proper land management and reforestation techniques are employed in conjunction with optimal fertilisation; that higher yields do not in fact incentivise the further conversion of forests into agricultural land; and that forest conversion would inevitably occur without intensification.

But given the huge nutrient deficit in most African soils and the enormous yield gaps preventing the achievement of food security, restricting the application of chemical fertilisers could actually exacerbate hunger and land degradation. That’s an option that seems most assuredly NOT climate-smart.


Where does this leave us? A rare breeze ruffles the leaves of Yorwataafaa’s meeting tree, and the babbling radio hanging from a branch sways gently. “The rains around here have changed,” he says with a nod. “They come late and stop early, before the crops have even matured.”

The fertilisers, however, change everything. “They have a lot of influence on the development of the crop,” Yorwataafaa explains. “If we get these fertilisers our crops develop faster, so by the time the rains are stopping we will have already harvested everything.”

Considering that, for one thing, many farmers see chemical fertilisers as both an adaptation mechanism and a path towards food security, and that for another, scenarios suggest some fertiliser-driven intensification could actually result in net emissions reductions compared to alternative land uses, this practice should not be stricken from the climate-smart list just yet.

Instead, local contexts and environmental circumstances need to be carefully analysed to know when chemical fertilisers are doing more good than harm, both for the farmer and for the climate.

Caity Peterson is a visiting researcher and science writer based at the Center for International Tropical Agriculture (CIAT) in Cali, Colombia, working on CCAFS Theme 1: Adaptation to Progressive Climate Change.