Soil Nutrient Focus for the Remainder of the Year

Since the Minister for Agriculture announced no change in fertiliser allowances during 2024 there has been a lot of farmers contacting their advisors to review their fertiliser allowances.

Farmers that have a nutrient management plan/fertiliser plan/derogation plan will know their chemical fertiliser limits in regards to Nitrogen, Phosphorus and Potash. These plans use the data from soil samples taken from the farm, plus the stocking rate on the farm and the application of all slurries/FYM spread back on the farm to work out what level of chemical fertiliser is allowed to be spread. When these plans are followed it concentrates the missing nutrients so that the target soil indexes reach index 3 or 4 for P and K and brings the soil pH to above 6.3. This then allows the optimum production of grass grown on the farm while still reducing greenhouse gas emissions and the risk of losing nutrients to the water.

Once you know what quantities and type of fertilisers you have already spread this year, the balance can be worked out. Assuming appropriate soil temperatures and weather conditions going forward we can anticipate a better response to nutrients spread in the coming weeks rather than waiting until closer to the end of the spreading season. All chemical fertiliser must be applied before the 15^th of September. Teagasc research has already proven that for every 1kg of nitrogen applied it gave a response of 27kgs for August, 19kg for September and 10kgs for October of grass. This means for the fertiliser you are going to apply for the remainder of the spreading year, you will gain a higher return if spread earlier rather than later. 

Farmers have made great progress in regards to improving water quality improvements and we know that Agricultural GHG Emissions are down 4.6% for 2023. With this in mind we also know of lower grass growths this year and the importance of having enough fodder for the winter period. This gap in the fodder budget can be tackled at by applying the correct fertiliser at the correct time.

Potash, K is known as a fertiliser for the second half of the year. With this in mind one of the Teagasc Tirlan Future monitor farmers Jack Kearney farming outside of Rathcormac, Co Cork has a plan to address this deficiency on their farm. Jack’s overall soil fertility on the farm is optimum for 55% of the farm for P, K and pH. Jack knows he has no P allowance for the farm but after reviewing his NMP with his advisor he knows what N, K and lime is required for the whole farm. He has looked at his NMP maps and knows what paddocks need to be targeted. Jack will spread lime on paddocks that has a pH of lover than the optimum pH of 6.3. This means 0.5 to 1 tonne of lime will be spread per acre in the next few weeks. With having no P allowance the choice of fertiliser used will be 19-0-15 plus Sulphur. This fertiliser will be good to help build low K soils and also to optimise grass growth. Milk, meat and grass removes kgs of P and K and it is important to replace them.

It is also important to have your slurry tanks emptied before the end of September. Kearney’s did not get an opportunity after 2^nd cut silage to spread the remainder in the tanks. They have 50 units per acre of 19-0-15 spread for 3^rd cut silage and the plan is to spread all the remaining slurry and FYM on this ground to replace any missing P and K once the 3^rd cut is removed.

The main advice for farmers for the remainder of the year is to:

• Know where the missing nutrients are required,
• Have a plan on how a combination of both chemical and organic fertilisers can optimise growth and replace missing nutrients
• Adhere to the buffer zones beside your rivers/streams
• Maximise grass growth and minimise losses to any water bodies
• Get a fodder budget drawn up for your farm

If you require any further details on what your N, P, K and lime requirements for your farm or to have a fodder budget drawn up, please contact your Teagasc or agricultural advisor.

Author: Sandra Hayes Coordinator of the Teagasc Tirlán Future Farm Programme

First Published 31 July 2024