GrowthWatch: Awaiting a grass growth bounce after recent rainfall

By Teagasc’s Seán Cummins and James Fitzgerald

As mentioned in last week’s GrowthWatch article, the majority of farms in the Teagasc Green Acres Calf to Beef Programme were suffering from a ‘green’ drought.

In more severe cases in the east of the country, grass was beginning to turn brown and growth has been severely affected.

However, the much-needed rain that was received from Wednesday through to today in many parts of the country will be a help.

The extent of which it drives growth though will depend on the pre-existing soil moisture deficit, the quantities of rain actually achieved and the farm’s average farm cover.

Maintaining an average farm cover of >500kg/ha is critical to growing grass. Remember, grass grows grass and if the farm is ‘skint’ with very low covers, the growth response rate will be much lower.

In some cases, the average farm cover did drop below the 500kg/ha mark. Despite demand being reduced and the introduction of silage, some farms were in a position where grass covers ‘melted’ on account of dry conditions and began to regress.

[grass_growth_map from=”2020/06/10″ to=”2020/06/16″]

These farms were also hit with a double whammy in that any paddock that was grazed had significantly reduced growth rates.

In situations where this occurred, silage supplementation will have to continue for another seven-to-10 days and it will depend on the farm’s grass growth response rate and how quickly the farm can once again climb back to an average farm cover of 500kg/ha.

In other areas – not nearly as severely affected by the drought – a decision may be made on whether or not to discontinue supplementary bale silage feeding.

However, this will depend on growth being higher than demand and the average farm cover available.

The farm burnt up badly over the last couple of weeks and growth has been severely limited. Last week the farm grew 15kg DM/ha, with demand sitting at 34kg DM/ha.

On account of the halving in grass growth rates, the decision was made to offer store cattle and suckler cows 50% grass and 50% grass silage diets.

I had previously been offering the store cattle silage in each paddock to extend the rotation to 25-30 days, but with the lack of rain over recent weeks it was near impossible to stop farm cover dropping.

The autumn-born calves have been moved to after grass away from the main grazing block and this has helped to reduce demand by 12kg DM/ha; but the severe lack of moisture has all but stopped growth.

Ideally, I would have liked to have more of this ground closed for second cut, but with the conditions over the past month, it just had to be grazed.

Hopefully, the rain over recent days will encourage grass growth once again and I’ll enter a position where silage supplementation can be ceased.

No fertiliser has been spread since June 3, when 47% of the grazing ground received 20 units of SulCAN. On account of the dry conditions, this fertiliser has yet to be used, so any further applications will be delayed until the growth response from the rain over recent days can be assessed.

Over the last few weeks, grass growth has managed to do just enough to keep grass in front of stock, but it has been really difficult to keep the quality of this grass high.

Since the last time of writing – which was six weeks ago – the grass growth rate has consistently been circa 45kg DM/ha/day.

This has done just enough to equal the demand for grass and so the average farm cover has remained at circa 865kg DM/ha over this time which is on target.

I am currently spreading one bag/ac of CAN after grazing which is helping to keep grass growth rates up. The temptation is there to top some of the stemmy paddocks after grazing to try and get better grass quality next time, but I held back from doing this so far, as it could set back regrowths too much.

If things pick up in terms of grass growth rates over the coming weeks, I will be back cutting and baling what gets ahead of the stock and this will help to improve sward quality. The extra silage will also be more than welcome.