Now is a Good Time to Apply Lime to Grassland

Application of lime this autumn while soils are dry and trafficable is ideal because as the winter rains will help to move the lime into the soil where it can do its work, leading to improved soil structure and nutrient availability in spring for healthier grass growth. Delaying liming until spring will mean early grass growth on low pH soils will be compromised. In particular the plant availability of phosphorus, the most expensive macronutrient to purchase, is limited by low soil pH.

Research has shown that for every €1 invested in lime, farmers can expect a return of between €6 and €10. With dairy, beef, and sheep farmers’ incomes forecasted to be strong this year, investing in lime represents a smart financial decision that will pay back many folds over the coming spring and years ahead. Therefore, now is an ideal time to put a liming plan in place and make the most of this high-return investment.

The benefits to liming pastures that are low in pH are as follows:

• Grassland soils can release up to 80kg N/ha (nitrogen per hectare) (64 units N/acre) per year, once restored to soil pH 6.3.
• Increase the availability of soil phosphorus (P) to the grass sward
• Annual grass production can be increased by 1.0 to 1.5 tonnes of grass dry matter (DM)/ha where soil pH was increased from pH 5.5 to 6.3.
• Increased persistence and productivity of both perennial ryegrass and clover.

Lime should only be applied based on a recent soil test report. The target soil pH for grassland (mineral soils) grass only swards is greater than 6.3, for grassland (mineral soils) for grass-clover swards a higher pH is beneficial, target reaching pH 6.5 to 6.8, and for grassland (peat soils) the target is 5.5 to 5.8.  Don’t exceed 7.5 tonnes per hectare (t/ha) in a single application. Soils with high molybdenum status may give rise to copper deficiency in grazing animals. To reduce elevated molybdenum levels, maintain a somewhat lower soil pH 6.0 to 6.2.

As a rule of thumb 2.5 t/ha (1.0 t/acre) application of lime will raise pH by about 0.3 units on a medium textured mineral soil, so therefore if the pH is 5.7, an application of 5 t/ha (2 t/acre) will raise the pH to approximately 6.3.

Calcium ground limestone is the most common form of lime and best value liming material. Some 35% of ground limestone is broken down and utilised within 6 months, while 65% can take up to two years to break down. It allows for steady pH adjustment.

Where needed lime should only be applied if ground condition allows. If ground conditions on your farm this autumn are not suitable for travelling, then lime can still be applied early next spring when an opportunity presents. Plan to apply and you will see the benefits over the course of the season.

In conclusion, liming soils this autumn will bring major benefits in terms of soil nutrient availability for grasslands next spring, and the more efficient use of nutrients applied for grass growth next year. Apply lime this autumn to unlock grass and grass-clover sward growth next spring and throughout the year.