Scientists from the University of Sheffield, in Paris for the COP21 climate talks, have revealed that the world has lost a third of its arable land in the past forty years. Soil loss is an “unfolding global disaster”, the researchers said, and, though 2015 has been dubbed the UN’s International Year of Soils, the precious resource still enjoys virtually no protection in Europe and much of the wider world.

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However, it may not be too late to save arable soils; Prof Cameron and his colleagues believe that some practices from the past, almost abandoned by intensive agriculture, could be key to securing soils for future generations of food producers.  

They believe human excrement could be used as an organic fertiliser, with a much smaller footprint than synthetic, non-renewable fertilisers. Plant biology professor Colin Osborne elaborated, “Historically, good soil management was supplemented by the collection and application of ‘night soil’, which is human excrement – a practice that continued into the 20th century.

“In a historical example of the circular economy, this closed the nutrient loop, recycling organic nitrogen and phosphorus back into soil.”

Professor Cameron and his team believe that a sustainable model for agriculture is founded on three principles:

• Managing soil by direct manure application, rotating annual and cover crops, and practising no-till agriculture (not cultivating and preparing the land). These practices connected to ‘conservation agriculture’ restore soil organic matter, structure, water-holding capacity and nutrients, averting soli loss while benefiting crops.
• Using biotechnology to wean crops off the artificial world we have created for them, enabling plants to initiate and sustain symbioses (close interactions) with soil microbes. These symbioses allow crops to exploit microbial biology to tap into soil organic nutrient reserves, and prime plants to better defend themselves against pests and diseases.
• Recycling nutrients from sewage in a modern example of the circular economy. Inorganic fertilisers could be manufactured from human sewage in biorefineries operating at industrial or local scales. A number of technical challenges impede the immediate adoption of this idea, but these can readily be addressed through research.

Speaking to the Guardian, Prof Cameron said the team’s vision will require including pastureland in rotations to make more land available for growing food, but reduce the burden of intensive cropping, and that their desired shifts will require government intervention and support for farmers to pull off. The professor said that before long, unless the trajectory of the food system is altered, “soils [won’t be] fit for anything except for holding a plant up.” He said, “We aren’t quite at the tipping point yet, but we need to do something about it. We are up against it if we are to reverse this decline.”

Though the researchers acknowledged that certain crops, climates and geographical areas may be better adapted to their vision of sustainable agriculture, and any solutions would need to be flexible, Prof Osborne believes that “A sustainable soil-centric reengineering of the agricultural system would reduce the need for fertiliser inputs and pesticide application, and require less irrigation, thus contributing towards safeguarding finite natural resources.”