How long before grass growth rates return to normal levels?

If a decent level of rain comes, it will be four weeks before sustained grass growth rates are achieved, Teagasc’s Dr. Michael O’Donovan said at a recent meeting of the Inter-Agency Fodder Committee.

As no significant levels of rain are forecast over the coming seven days, O’Donovan hinted that it could be pushed out by another week – five weeks in total.

However, he noted that grass growth rates tend to bounce back after a drought, adding: “I’ve looked at grass growth curves coming out of droughts and the response in September could be up to 30kg of grass dry matter per kilogram of nitrogen applied.

“You get a response in the months following a drought, so to me there’s huge potential to grow more grass.”

Teagasc’s Dr. Siobhan Kavanagh also presented data from a modeled scenario, which showed the potential to save surplus grass at growth rates of 30kg/ha/day in August; 56kg/ha/day in September; 38kg/ha/day in October; and 19kg/ha/day in November.

Basing the work on a dairy farm stocked at 2LU/ha and using 5kg/cow/day of concentrates to keep the daily demand for grass at 10kg/cow/day, she said there’s potential to save grass as silage.

“There’s the potential to have a surplus of 1.6t/ha of dry matter. If you take that over a 40ha farm, that’s potentially 200t of silage – allowing for a 75% utilisation.

“There’s that potential there and that’s assuming we get rain on August 1, fertiliser is maximised and cows are restricted on grass. There is the potential to conserve additional grass before the winter.”