Dr. David Wall, Enterprise Leader of the farms and estate at Teagasc’s Environment Research Centre in Johnstown Castle, joins Stuart Childs to discuss the timing of fertiliser applications over the coming weeks to maximise the return from nutrients applied while minimising the risk to water quality.
This is particularly important in drought-affected areas, where low grass growth and reduced nutrient uptake have increased the risk of nutrient losses.
David first addresses the concept of calendar farming, explaining that fertiliser deadlines are driven by declining nutrient uptake rather than soil trafficability. As daylight levels fall, grass growth and nutrient demand naturally decrease. Applying additional nitrogen above crop requirements will not generate extra growth and, particularly from mid-October onwards, will instead increase the risk of nutrient losses.
Following the recent drought, David says farmers should make the most of natural soil mineralisation over the coming weeks. With moisture returning while soils remain warm, mineralisation can supply approximately 1 kg N/ha per day, potentially supporting around 35 kg DM/ha per day of grass growth.
Lime also has an important role to play. Correcting soil acidity can improve nutrient availability and help release significant quantities of soil nitrogen over time, which can then support further grass growth.
Despite the temptation to apply heavily now that the drought has broken, David advises farmers to use fertiliser and slurry sparingly and avoid over-application. In drought-affected areas where growth has resumed, applications of around 20–25 kg N/ha from fertiliser or slurry can provide additional growth on top of what soil mineralisation is already supplying.
Slurry should also be prioritised where appropriate, particularly where tanks need to be emptied before October. David recommends applying slurry regularly over the coming month ahead of the closing period commencing on October 1st.
This approach will help maximise the return from the nutrients applied, reduce the risk of losses to water and also help spread contractor workloads over the coming weeks.
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