Greater efficiency in the way fertilisers are used and improved agronomic decisions could help farmers take the required steps to reduce carbon emissions and meet Government commitments – which are currently lagging far behind targets, reported Mark Tucker of Yara. He believes a better understanding of the process of N₂0 release – which is 300 times more polluting than CO₂ – could help growers mitigate the effects.

The conversion of fertiliser sourced ammonium into nitrate releases some N₂0, but if the nitrate converts to nitrite, then releases can be far more significant, he reported. “That is likely to happen quickly if soil becomes waterlogged, creating anaerobic conditions. And it will be greater if there are high levels of nitrate in the soil when it happens.

“That has implications for soil management to avoid anaerobic conditions, including organic matter levels and improved cultivations, as well as fertiliser application rates and timing to minimise the risk of excessive nitrates remaining in the soil.”

Mr Tucker also pointed out that whilst urea fertilisers may appear to have a relatively low carbon footprint from their manufacture, they can incur high losses in the field. Where growers increase application rate to allow for 20% loss through volatilisation, the final carbon footprint (CF) could be as much as 50% higher than ammonium nitrate, for example. If the same rate of N is applied, the CF could still be 15% higher with urea, and there would be less available nutrient for the crop, he added.

“If growers are selling their carbon footprint bin terms of  Kg/CO₂ per Kg of produce, then yield will be paramount in delivering low figures; i.e. efficiency of use. Without Sustainable Intensive Agriculture increasing yields and productivity, emission losses would be four to five times higher than they are now,” he said. “Growers have already improved fertiliser use efficiency from 35%, to more than 60%. And we are continuing to drive that down with good practice.”