Nitrogen: no easy fix

Products that claim to herald a nitrogen revolution that will boost global food production are nothing more than snake oil, say scientists.

- Roelof Bezuidenhout reports.

Companies, including a big global player, are bringing biological products onto the market in South Africa and elsewhere that supposedly fix nitrogen (N₂) in grains and other non-legumes. In all likelihood, these products do not fix N₂ in any agronomically significant quantities. The products are plainly based on flawed science, according to Prof Linus Franke of University of the Free State’s Department of Soil, Crop and Climate Sciences.

“The bacterial strain in at least one of these products doesn’t even have the basic genome required to fix nitrogen. It may provide other benefits to crops; it is known to release plant hormones that may stimulate root development, for instance, but it does not fix nitrogen.

“One of the products even makes the claim of ‘converting greenhouse gases to fertiliser’. They are getting the science all wrong,” says Franke.

“One must raise questions about the admission regulations for these biological products, in general, and how they can be improved. When farmers apply a registered herbicide correctly, and there is no herbicide resistance among weeds against the active ingredient, they may be quite sure the herbicide does the job. However, with biologicals there is no such guarantee. Some biological products do provide benefits to plant growth, but it is often under specific conditions only, and the evidence of how and under which conditions the product works is usually missing.” Franke is supported by the review, ‘Science losing its way: examples from the realm of microbial N₂-fixation in grains and other non-legumes', which points out that growing concerns about the effect of intensive agricultural practices on climate change, human health, biodiversity, and soil degradation have led to increased interest in alternatives to agrochemicals to provide nutrients and protect against pests and diseases.