BOTH NEW and old research have shown that liming benefits crop growth, whilst at the same time reducing emissions.

With the industry aiming to reduce its carbon footprint drastically over the next 10 years or so, this is seen as a way that farmers increase productivity in grassland, whilst positively impacting the environment.

According to Philip Cosgrave, a grassland agronomist at Yara, the latest research in Ireland has shown that liming can make a big difference.

Philip Cosgrave says the benefits of liming are now well-proven

Philip Cosgrave says the benefits of liming are now well-proven

“When liming and increasing soil pH, we see a significant reduction of nitrous oxide (N2O) emissions,”he said. “This occurs alongside increased grassland productivity.”

Liming is a widely used agronomic measure to improve acidic soils and maintain optimal soil pH for high crop productivity. Mr Cosgrave explained what the trial results showed in terms of limiting environmental impact while fostering robust grass yields.

In the trial, soil at the trial site was classified as acidic, with a pH of 5. Consistent liming over a period of 10 years had resulted in a change in soil pH, with the new figure ranging from 5.0 to 6.9.

“Increasing soil pH by liming resulted in a clear reduction of N2O emissions as well,” said Mr Cosgrave. “We also saw increased grassland productivity compared to the un-limed plots, despite utilising the same management and nitrogen fertiliser regime.”

The amount to which N2O emissions reduced depended on the quantity of lime applied during the experiment.

As the soil pH rose, the difference became even more stark. At a soil pH of 6.9, N2O emissions went down by 39% compared to those at a pH of 5.0. Measuring grass yields showed that the best results were achieved when combining liming with regular phosphate application.

Improved plant growth and the lowering of greenhouse gas emissions were not the only benefits of liming. Mr Cosgrave explained: “Liming increased the activity of soil microbes and the availability of nutrients, most notably phosphate.

“This leads to improved plant growth, complementing the environment created by an optimal soil pH.”

Plots limed to pH higher than 6 had 0.5 t/ha higher dry-matter yields, while the limed plots with optimal P content had 1.5 t/ha higher yields on average, compared to un-limed soils with low P measurements.

“This research will hopefully be used to support an even further increase in the use of optimum soil pH for grassland on farms with high grass yields,” added Mr Cosgrave.

“Liming is a common measure for optimising crop productivity, but evidence shows that doing so will also help your farm make a positive environmental impact.”