Liming policy vital in efforts to tackle global warming

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According to Dr Debbie McConnell, from the Agri-Food and Biosciences Institute (AFBI), maintaining grassland soils at their optimal pH level will help maximise the amount of carbon sequestration achieved by the farming industry as a whole.

Increasing the carbon storage capacity of soils is now widely regarded as a fundamental way of mitigating the impact of greenhouse gases on our climate.

Grassland accounts for 91% of the farmed area in Northern Ireland. McConnell spoke at this week’s EU Sustainable Dairy Sustainable Symposium, held at CAFRE Greenmount.

She said: “Many of our grassland soils are too acidic: they require lime. Research has confirmed that bringing these soils up to their optimal pH level will significantly improve the amount of carbon sequestration achieved.”

But this is only part of the story. According to McConnell, upping the pH will also deliver a grassland production response.

She added:“Farmers can expect to secure a 5:1 financial return, if they commit to a regular liming policy. This figure is based solely on the increased levels of grass output that farmers will secure under such circumstances.”

Conference delegates were told that carbon sequestration is driven, for the most part, by the level of microbial activity found in soils. McConnell also confirmed that a targeted fertiliser strategy will help deliver this objective on all farms.

“The focussed use of nitrogen will specifically boost microbial activity in soils,” she commented. “AFBI research has confirmed that grassland soils can actively sequester carbon for up to 50 years. Up to now, it had been thought that sequestration activity will level off after 20 years.

“However, a trial at AFBI Hillsborough, which got underway in 1970, is confirming that sequestration rates of up to 0.86t of carbon per hectare per annum can still be achieved in 2019 from grassland soils that have continuously received moderate levels of cow or pig slurry on an annual basis.”

The AFBI research scientist said that regular grassland re-seeding will not impact on a soil’s activity to sequester carbon.

She added: “The increased level of microbial activity will more than compensate for the enhanced level of soil respiration that is recorded directly following the establishment of a new sward.”

McConnell concluded; “Improving soil quality is a win:win scenario for farmers. This approach will deliver both improved production levels and enhanced carbon sequestration rates

“Securing this objective requires the precision use of soil and plant nutrients.”