Considering current fertiliser prices, optimising your soil pH has never been more important. Having an optimal soil pH ensures that applied nitrogen (N), phosphorus (P) and potassium (K) are used as efficiently as possible.
Lime has a critical role to play in this, as it increases the availability of key nutrients that are already in the soil for plant uptake.
Applying lime and improving soil pH facilitates a reduction in N application due to improved nitrogen use efficiency (NUE).
NUE is the ability of crops to take up and utilise nutrients for maximum yields.
NUE works in line with the government’s Climate Action Plan 2021, which sets out a target to reduce greenhouse gas emissions from Irish agriculture by 22-30% by 2030.
To achieve this target reduction, a suite of measures has been outlined. One of the targets is to reduce chemical N fertiliser use by 20% by 2030.
To support these targets with the best liming solution, all Grolime certified companies are licenced by the Department of Agriculture, Food and the Marine (DAFM) to manufacture and sell ground limestone for use as a soil conditioner in Ireland.
You can’t manage what you don’t measure: The starting point to reducing chemical N fertiliser use is to know the fertility status of your farm.
Teagasc recommend taking soil samples every two years after the application of lime, as this will help you to better target fertiliser use to achieve greater grass/crop performance and ultimately minimise waste.
One of the key and most important tasks arising from soil sample results is to identify areas of the farm that require lime. Soil sample results also identify the P and K levels in the soil.
Target soil pH for different crops Crop type Target soil pH Grassland (mineral soils) grass-only swards ≥6.3 Grassland (mineral soils) with clover 6.8-7.0 Grassland (peat soils) 5.5-5.8 Cereals ≥6.5 Beet/beans/peas/oilseed/maize 6.8-7.0 High molybdenum (Mo) soils 6.0-6.2
Benefits of applying lime
Growing as much grass as possible is a great opportunity to reduce on-farm costs.
Soils maintained close to the target pH will have the benefits of increased grass yields, more efficient utilisation of applied fertilisers and manures and better persistence of more productive species in the sward, i.e. perennial ryegrass and clover.
Limed soils also tend to release more nitrogen from the soil organic matter facilitating improved NUE.
Applying lime every couple of years will help improve grass availability, raise soil pH and help condition the soil; this in turn will improve nutrient availability and soil structure.
With better soil structure comes improved drainage, which allows for better root development and nutrient uptake. Lime should be applied to tillage soils based on the most sensitive crop to lime in the rotation.
One of the biggest and most valuable benefits is the increase in NUE.
The concept involves two major processes in plants: Uptake and utilisation of nutrients. Correcting soil pH alone will result in an improvement in NUE from 35% to 53% where soil P and K is sub-optimal.
With record fertiliser prices and limited supplies, spending money on lime to correct soil pH will ensure a better return from each kilo of N applied. Teagasc have valued the return on investment at €6-10 for every €1 invested in lime.
How lime works
Lime is a soil conditioner and controls soil acidity by neutralising the acids generated from N fertiliser, slurry applications and high rainfall. Soil pH has a large influence on soil nutrient availability.
Applying lime improves soil pH, which increases grass production annually by releasing up to 80kg more N/ha/year, unlocking soil P and K and increasing the response to freshly applied N, P and K.
Other benefits include an increase in earthworm activity, improvement in soil structure and grass is more palatable to livestock.
Clover requires a higher soil pH
Recent trial work carried out by Teagasc has shown that by increasing the soil pH from 5.5 to 6.8 for clover swards increases the productivity from 8t/ha up to 9.5t/ha dry matter.
Boosting clover productivity in the sward reduces the requirement for chemical fertiliser N. Therefore, aim to maintain a higher soil pH for clover swards to increase N fixation during the growing season.
In addition, where it is planned to establish clover swards, aim to correct soil pH levels in advance of reseeding to ensure fast and successful clover establishment.
Grolime is the voluntary certified trademark under which companies who meet necessary criteria are authorised to promote and sell their ground limestone.
All Grolime companies undergo independent twice-yearly testing for Total Neutralising Value, Moisture Value and Grading, which is in line with the national specification for ground limestone.
Therefore, it is essential you source your ground limestone through a Grolime supplier.
To find your local Grolime supplier, click here.