Liming grassland this autumn could offer greater financial benefits than usual as fertiliser prices soar.
Grassland specialist George Fisher, of the AHDB Grass Campaign, is urging growers to check soil acidity – and to apply lime between now and Christmas if pH falls short of the optimum,
This will achieve a greater financial payback this year as fertiliser prices reach a new record high. The price of ammonium nitrate has doubled since the beginning of the year – and could rise further before falling back.
In contrast, Dr Fisher says the price of lime remains relatively stable, providing an even better return on investment than in previous years.
Optimising soil 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.
Raising the soil’s pH to its optimum by liming will not only increase its ability to release nutrients to the growing crop, but it will 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, says Dr Fisher.
All of this has been reflected in long-standing research, which shows grass yield can be 30-40% lower as pH drops 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.
This highlights 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 soil, a bag or livestock –are at the optimum availability for plant 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.”
Once the pH is known, the amount of lime required can be determined using the Agricultural Lime Association website www.aglime.org.uk. It has a lime calculator to specify the tonnage of different products needed for different soil types.
Dr Fisher says it is not so much an issue of which product is used – with choices ranging from basic crushed lime direct from a quarry to enhanced, granulated products. Farmers should opt for calcium-based products, rather than those based on magnesium.
“You can work away on the physics and biology, but if you don’t have the pH right, you will still lose nutrients. But get them all right and you reduce your chances of nutrient loss, leaching and pollution – and increase your chances of a healthy, high-yielding crop.”
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