Advising growers that liming arable land and also grassland this autumn could offer greater financial benefits than usual due to soaring fertiliser prices, the Agricultural and Horticultural Development Board (AHDB) has urged growers to check soil pH, and if it falls short of the optimum, to apply lime between now and Christmas.
Dr George Fisher, a grassland consultant with the AHDB said that while the price of ammonium nitrate has more than doubled since the beginning of the year, in contrast the price of lime had remained relatively stable, providing an even better return on investment than in previous years.
“Optimising a soil’s pH will ensure its nutrients are available to the growing crop rather than lost through leaching or locked up in an inaccessible form. This has environmental as well as financial benefits,” said Fisher.
He said that raising the soil’s pH to its optimum by liming would not only increase its ability to release nutrients to the growing crop, but would also optimise conditions for the soil’s biology and health.
“This results in less wastage of expensive nutrients, less pollution into water courses and an improved soil structure, with all its associated benefits.”
He said that years of research had highlighted the fact that grass yield could be 30-40 per cent lower as pH dropped from the optimum 6.5, down to 5.5.
“Further gains from optimising pH include the more efficient capture of nitrogen by legumes while a growing body of evidence is beginning to suggest soils with a low or high pH can lose more carbon.”
All of these factors, he said, pointed towards the importance of measuring the pH of all grassland soils, and optimising pH at close to 6.5.
“This ensures that all nutrients, whether from the soil or a bag or from livestock, are at the optimum availability for the plant to take up, provided everything else is in place.
"It doesn’t matter when you lime if ground conditions are suitable, but if you do it now, at the end of the grazing season, it has the winter to work its way into the soil and positively impact the pH next season.”
And he pointed out that once the pH was known, the amount of lime required could be determined from the Agricultural Lime Association’s website where a ‘lime calculator’ would specify the tonnage to be applied to different soil types and through a choice of products.
The consultant pointed out that choices of product ranged from the basic crushed lime direct from a quarry to enhanced, granulated products.
And he said that while all these would work, he reminded growers that soil health was about chemistry (its nutrients), physics (its structure) and biology (its microbial life).
Fisher said: “You can work away on the physics and biology, but if you don’t have the pH right, you will still lose nutrients.”