Fertilising First cut grass silage

By Sean Mannion ,

Drystock Advisor,

Teagasc Ballinasloe.

Recent weather may have delayed the closing of some silage ground with poor grazing conditions and fertiliser applications unsuitable in many areas. Ideally some of the silage ground would have been grazed by now to promote optimum regrowth and remove any dead material. This task is easier achieved for those with sheep or lighter cattle.

The silage crop needs to grow quickly in a 6-7 week period to maximise the energy value of this grass ensiled in a silage bale or a pit.    

Nitrogen (N) is the key driver of grass yield. Grass swards with high levels of perennial ryegrass will use N more efficiently than older swards. Recently reseeded swards (0-3 years) will have 25% higher N demand. These swards will generally produce higher yields also to compliment this. In relation to Phosphorus (P) and potassium (K), you can’t manage what you don’t measure. Accurate soil analysis is the basis of determining what rate if any of these nutrients are required to grow your crop of grass and to get the optimum from fertiliser and or organic manure you apply. Silage fields should be prioritised for slurry spreading as crop removal takes its toll on these nutrients from these fields and needs to be replaced, slurry & farmyard manure offers a huge role in this replacement followed by chemical fertiliser. Low-Emission Slurry Spreading (LESS) is mandatory on all farms with a grassland stocking rate above 150kg/N/Ha. This is also mandatory for slurry produced and spread from pigs (e.g any farmer importing pig slurry)

From the 1st Jan 2023, no chemical phosphorus (P) is allowed on farms with a grassland stocking rate greater than 130kg N/Ha, unless there are valid soil samples to prove that the lands are P index 1, 2 or 3. Sulphur, grass silage crops require 20 kg S/ha per cut. Applying S to soils where it is required will improve grass DM yields and quality.

Teagasc provides a Local Advisory and Education service to farmers. They have offices based in Roscommon Town  (Tel: 090 6626166), Castlerea (Tel: 094 9620160) and Longford Town (Tel: 043 3341021), You can find us on Facebook @Teagascroscommonlongford, twitter @teagascRNLD and YouTube. And follow the hash-tag #RNLDwebinars for information about local farm webinars. Email; RoscommonLongfordAdvisory@teagasc.ie