Dairy Management: grass growth, fertiliser and open days

Grass

Heavy rain is forecast for this weekend and into next week. With the exception of those on heavy farms in the west and north, this rain is badly needed. As outlined here, there won’t be an instant response in terms of grass growth after the rain does come.

The two or more weeks for growth rates to pick up can be the most frustrating period of the dry spell and the more severe the deficit is, the longer it takes to recover.

While the dry spell is not near as severe as it was in 2018, the timing is probably much worse in that there is now a very high probability that there will be no big bounce in grass growth this autumn, unlike in 2018.

The worst period of this dry spell is yet to come. Up to now it has been very easy to manage stock, and animals are content at grass even at low covers.

When the rain does come there will be a release of background nitrogen and the grass physiology will change and become sour, meaning cows and other stock will become unsettled.

Those that are now feeding silage or meal outdoors may have to change tack if land gets wet and move to indoor feeding, which can mean more work.

Fertiliser

With very heavy rain forecast for some parts of the country over the weekend, all fertiliser and slurry applications should be delayed. There are still almost two weeks to go before the end of the closed period.

While question marks remain over how much nitrogen mineralisation will take place after soils re-wet, it’s unlikely that a lack of nitrogen will be the main impediment to growth in the short-term.

There is definite risk to spreading nitrogen on hard ground in advance of heavy rain, as there’s a fair chance it’ll be washed away.

Treat each field on a case by case basis when deciding on how much nitrogen to spread, if any. For fields with good clover content, spreading lime and/or 0:7:30 or 0:10:20 could be a better investment.

Fields that have been growing well all summer and are still green now won’t see much nitrogen mineralisation take place and so may require the higher rates of nitrogen at say 20 to 30 units of nitrogen per acre.

Fields that have been affected by the dry spell can probably get half this.

Sustainability

At Tuesday’s sustainability open day in Teagasc Johnstown Castle, there was a timely message on managing hedgerows. Just because the hedge cutting season opens on 1 September doesn’t mean that hedges should be cut now.

The longer they are left uncut the better. Farmers in derogation can only cut hedges on a three year cycle and must leave at least one thorn tree to mature in every hedgerow.

If cutting the top of a hedge, make sure the top is at least 1.5m above ground level. Other farm walks and events coming up include;