The Ag Climatise policy document highlighted the need to decrease chemical nitrogen (N) fertiliser use on Irish dairy farms, and thereby reduce the environmental impact of dairy farming, both in terms of greenhouse gas (GHG) emissions and water quality.
Dairy farmers visiting the upcoming Teagasc Dairy Open, which commences today (Tuesday, September 14) in Moorepark and is repeated tomorrow, Wednesday, 15 and again on Thursday, September 16, will hear from Teagasc researchers and advisers about the five key practices which can be used to reduce N fertiliser use on all farms.
Registration is essential and you can book your place at here.
The five key practices are:
- Replace N fertiliser in early spring on up to two thirds of the milking platform by using Low Emission Slurry Spreading (LESS);
- Measure farm cover weekly to see how much grass is on the farm. Use this information with the grass growth prediction available from the MoSt grass growth model to predict grass supply for the week ahead. If growth is surplus to demand, N fertiliser application could be reduced;
- Soil fertility – ensure that soil pH is >6.2 and both Phosphorus (P) and Potassium (K) are index 3. Nitrogen use efficiency is greater in soils with optimum fertility;
- Are you making baled silage in every rotation? Particularly in July and August? If you are then grass growth exceeds demand and N fertiliser application can be reduced;
- Swards dominated by perennial ryegrass are more productive and have greater N use efficiency. Consider reseeding poorly performing swards.
Teagasc research indicates that N fertiliser application can be reduced in grass-white clover swards with clover content of more than 20%, while maintaining herbage production, and increasing animal production (Table 1 below).
Table 1: Results from research at Moorepark and Clonakilty
Moorepark1 Clonakilty2 Grass-only 250 kg N/ha Grass-clover 150 kg N/ha Grass-only 250 kg N/ha Grass-clover 150 kg N/ha White clover content (%) – 22.0 – 16.8 Grass production (t DM/ha) 13.5 13.4 15.1 14.4 Milk yield (kg/cow) 6,068 6,331 5,521 5,744 Milk solids yield (kg/cow) 490 510 470 487
Establishing white clover requires a combination of reseeding and over-sowing. A full reseed is the most reliable method of establishment as it gives white clover a better chance to establish and provides the best opportunity for weed control.
Over-sowing is a simple and low cost method, but success is dependent on weather conditions around the time of sowing, soil moisture, post-sowing grazing management and competition from the existing sward.
Some key points when using both methods include:
- Ensure optimum soil fertility (i.e. pH > 6.3, index 3 for P and K);
- Reseed/oversow in spring/early summer;
- Graze swards at a low pre-grazing herbage mass (<1,100kg dry matter (DM)/ha) and graze tight (≤4cm) for at least the first three grazing’s post-sowing/over-sowing;
- Avoid over sowing old swards with a low perennial ryegrass content – a full reseed is best in these conditions.
This work is being carried out by Teagasc Researchers Brian McCarthy, Deidre Hennessy and Michael Egan who are based at the Teagasc, Animal and Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork.
If you wish to attend the Teagasc dairy open day in Moorepark on one of the following days – Tuesday 14, Wednesday 15 or Thursday 16 – pre-registration is required and can be done here.
