Farming: Scientific study shows fertiliser use could be cut

A new report which claims that lower levels of fertiliser can produce high crop yields if supplemented by practices such as the use of animal manures, crop rotation and legumes has been criticised for “teaching farmers to suck eggs”.

Dr Chloe MacLaren

The report published in the journal Nature Sustainability saw workers from Rothamstead Research use a meta-analysis of 30 long-running farm experiments from across Europe and Africa to mine the raw data from experiments carried out over several decades.

The report found that, by using traditional practices in association with more limited amounts of fertiliser, acceptable yields could still be achieved – whereas they did little to increase yields when high fertiliser levels were used.

The lead author of the report, Dr Chloe MacLaren of Rothamsted Research said the findings showed that adopting some, or all, of these approaches could help reduce and rebalance worldwide fertiliser use, a global imperative given spiralling prices caused by the war in Ukraine.

“Reducing reliance on chemical fertilisers would help to buffer farmers and consumers against economic shocks, such as the current spike in fertiliser costs and consequent increase in food prices,” she said.

“Widespread uptake of these practices could also contribute to a more equitable global distribution of fertiliser,” she claimed pointing out that the average nitrogen fertiliser rates in Africa were a small fraction of those in Europe, with smallholders in particular using much less than their fair share.

“If fertiliser use is reduced where it is currently high, then fertiliser use could be increased where it is currently low - addressing food security issues without exceeding planetary boundaries.”

But MacLaren admitted that the increased use of man-made fertiliser in the last 60 years had helped feed the rapidly expanding global population, but she added that it had not come without a cost, claiming cases of water pollution, climate change emissions, and biodiversity loss could be partly attributable to excessive fertiliser use.

However farmers, commenting on social media, said it was good that the scientific community had finally caught up with Turnip Townsend who had espoused the use of crop rotations including crops such as beans and peas - along with growing of turnip crops to support more animals for their manure over the winter which could then be recycled to improve yields- back in the 1730’s.

The new report also found that while all organic matter improved soil structure and added to nitrogen availability, manure was found to have a considerably greater impact on yield than adding plant-based composts or cuttings, or leaving the remains of crops in place after harvesting.

This caused another farmer to note that while many of the more radical elements involved in the climate change debate were keen to see a global reduction in the number of cattle and sheep kept, it was refreshing to see that someone had realised that they did, indeed offer benefits.

However the report also admitted that any move to increase uptake of the prescribed practices were likely to require policymakers and society to create a more ‘conducive socioeconomic context’.