The correct use of agricultural nutrients; nitrogen, phosphorus and potash is of the utmost importance. It ensures money is not wasted on excess use of chemical fertilisers and helps to protect the environment and water quality, writes Aveen McMullan, Sustainable Land Management Branch, CAFRE.
Under the new Nutrients Action Programme (NAP) 2019-2022 you will require a soil analysis which demonstrates that there is a crop need for phosphorus before applying chemical phosphorus fertiliser. Furthermore from 1 January 2020 a fertilisation plan must be prepared by grassland farmers prior to the application of chemical phosphorus fertiliser, and also all farms using phosphorus rich manure (e.g. layer litter, pig farmyard manure) and anaerobic digestate.
Soil sampling is the first step to efficient nutrient management. A soil analysis determines the fertility of your soils, allowing you to plan manure, lime and fertiliser applications to maximise yield. Only 18% of soils analysed in Northern Ireland are at optimum fertility for pH, Phosphorus (P) and Potassium (K). Regular sampling will help correct this situation, allowing you to minimise wastage and nutrient loss and make full use of slurry and manure.
When is the best time to take soil samples?
The autumn through to mid-winter (October to February) is the ideal time for soil sampling provided there has been no organic manure, lime or bagged fertiliser applied in the previous three months. A single soil sample will be adequate for 4ha (10 acres) in one or more fields provided they are similar soil type and have been under similar management. This service costs approximately £9 including VAT per sample. It represents excellent value for money as it enables you to improve your soil fertility and plan ahead.
How should you carry out soil sampling?
Soil augers and sample bags are available from your DAERA Direct office.
• For areas similar in use and soil type, up to 4ha in size take 20-25 cores across the area. Avoid troughs, gates, headlands, manure patches and areas where stock shelter
• Mix the cores well in a bucket and place a representative sample of approximately 500g in a bag and label with your name, farm survey number and field number.
• Return the auger and samples to the DAERA Direct office with the payment
Samples will be sent to the laboratory for analysis and the results will be available usually within one week.
What can I learn from my soil analysis report?
1. Check the pH which shows if lime is needed.
Lime neutralises the acidity in the soil and improves the availability of nutrients to the crop and consequently crop yield. Applying lime can give you a return of between five and seven times the cost of this input. Acidity is measured on the pH scale. The pH scale is logarithmic so a pH of 5 is 10 times more acidic than a pH of 6. Always aim for the optimum pH.
Optimum pH - Grassland; Mineral Soils 6.0; Peaty Soils 5.3
Optimum pH - Arable; Mineral Soils 6.5; Peaty Soils 5.8
2. Check the Phosphorus (P) and Potassium (K) Index
P is vital for root development and is also important for the production and use of energy by plants to grow and develop. K, often referred to as ‘potash’, is an important nutrient for crops and grass, especially silage. It is critical to the uptake of nitrogen and also helps the plant maintain its water balance.
Whilst in general the optimum index for P is 2, for extensively managed grassland a P index of 2- is adequate. The new NAP regulations introduce new maximum phosphate fertiliser application limits for extensively managed grassland in Northern Ireland from 1 January 2020.
Chemical phosphorus fertiliser should only be applied where there is a crop need; that is where a soil analysis shows the P index is below the optimum for the crop grown, taking into account the phosphorus content of any organic manures applied. The optimum Index for K is 2-.
3. Plan Phosphate (P2O5) & Potash (K20) applications based on the recommendations
A soil analysis report will specify a recommendation for kg P2O5/ha and kg K2O/ha if they are required. These are maximum amounts and where possible should be supplied from slurry or farmyard manure. Only top up with the right chemical fertiliser at the correct rate if necessary to make up the balance.
The CAFRE Crop Nutrient Calculator available at: www.daera-ni.gov.uk/onlineservices can quickly and easily help you to determine crop requirement, the value of manures and it completes the application rate calculations for you. Further information on managing nutrients and understanding your soil analysis report is available at: www.daera-ni.gov.uk/5-steps-to-managing-nutrients
Take action this autumn!
Take this opportunity to get out and take soil samples, benefit from your soil analysis report – it may save you money on chemical fertiliser. Ensure you are compliant and fully prepared for applying nutrients next year.