Liming to improve soil health and nutrient availability
October 1, 2024
The wet start to 2024 follows on from poor conditions throughout summer 2023. This means liming opportunities could have been limited on many farms. Now is a good time for farmers to consider applying lime to productive grass and arable fields on their farms. With high periods of rainfall and consistent wet weather, water passes through the soil. Which can leach essential nutrients such as calcium, causing soils to become more acidic and less productive.
The College of Agriculture, Food and Rural Enterprise’s (CAFRE’s) arable ground is tested annually. Grassland fields are tested every three years to assess pH, identify any deficiencies and target lime, phosphorous and potassium applications to meet optimum crop requirements.
This autumn, where conditions allow, the farm will apply bulk ground limestone. This is based on recommendations from the most recent soil analysis report with a target of pH 6.2 for mineral grasslands (or pH 5.5 for peat soils). Arable fields on the farm are targeted towards a pH of 6.5 for mineral soils (or pH 5.8 peat soils). The target pH is 0.2 units above the optimum pH to allow for inconsistencies across a field.
The Hill Farm Centre at Glenwherry has land which is designated or classified as Species Rich Grassland. Lime is never applied to these fields as it will reduce the species composition from a biodiversity perspective and release Carbon to the atmosphere.
Lime contains calcium carbonate which when applied will raise soil pH and improve soil health. This increase in soil pH will ensure better use of nutrients – improving grass and crop productivity. Lime is also a soil conditioner. This improves soil structure and neutralises the acids generated from the mineralisation of nitrogen fertilisers. However, soils which are classified as peat with a very high organic matter, do not have the same requirement for liming. Over applying lime to peat soils can release carbon to the atmosphere. Causing an increase of greenhouse gas emissions and reducing diversity in species rich grasslands.
Farmers who have taken part in the Soil Nutrient Health Scheme in Zones 1 and 2 will have received their soil analysis reports. Therefore, they will be ready to act on the recommendations for lime this year.
Participation in the SNHS is now a conditionality of receiving future farm support. The scheme will allow you to correct deficiencies and cost-effectively apply nutrients in line with what your crop requires. Allowing you to improve farm productivity, economics and soil health. Further help on interpreting your soil analysis and making use of the results can be found in the SNHS training. This is available online at www.cafre.ac.uk/snhs-training.
Your soil analysis report will recommend the amount of lime each field requires to achieve optimum pH.
Points to bear in mind are:
- Prepare a farm liming plan based on your soil analysis report. If the recommendation is more than 2t/acre of lime to be applied, apply half now and half again next year or in two years’ time.
- Target fields with the greatest requirement first (the most acidic).
- Lime can be applied at re-seeding or cultivation. Incorporate it into the seedbed or on the surface of existing grass swards.
- Lime can be applied at any time during the year but ideally at the end of the year. Since applying slurry after liming can lead to a loss in nitrogen.
- Bulk calcium ground limestone is a persistent material which reacts longer over time. This is due to the larger particle sizes. Whereas granulated (prilled) lime products (less than 0.1mm particle size) are more reactive. These can be applied with a fertilizer spreader. At low pH levels, a bulk application is often needed to raise pH to the optimum. At higher pH levels, annual applications of granular products can be beneficial. This way, you can maintaining pH levels closer to optimum.
If you have not obtained a soil analysis report inside the last four years, aim to soil test your fields this winter and at least three months after your last slurry or fertiliser application.
For soil samples outside of the SNHS, bags and augers can be requested and collected through your local DAERA Direct office by phoning 0300 200 7850. You can then post off your soil samples and pay NRM directly by debit or credit card.