How to weather pasture damage

Thursday, August 02, 2012

The bad weather this year has damaged pasture, resulting in extra reseeding.

There has been a significant decrease in ryegrass, even in paddocks not badly poached.

Much ryegrass has become wispy and is going to seed at low covers. This is due to environmental stress, and a loss of nitrogen from the soil, in some cases.

Of course, where paddocks have been badly damaged there has been a drastic decrease of ryegrass, and bare patches are being filled up with creeping grass, or other poor-quality grasses and weeds.

In some heavy land areas, paddocks have been so badly cut up that complete reseeding will be necessary, and this should be done as soon as possible.

Some top-seeding of damaged patches may be adequate for other paddocks that have a good level of ryegrass and are fairly free of weeds.

During the very bad weather, many paddocks were under-grazed, and became stemmy.

It is essential that these paddocks are cleaned off as soon as possible, by topping or tight grazing, and that they receive adequate fertiliser.

Otherwise, they will not produce quality grass for the rest of the year.

Some of these under-grazed paddocks could be fertilised, and closed for a light cut of silage.

How Good is Your Grass

A Teagasc survey, over a few years, of typical farms on reasonably free-draining soil indicated that there is a huge range in production.

The top farms produced 14.4 tonnes of grass dry matter per hectare, while the lowest produced only 8.9 tonnes.

This is a difference of 5.2 tonnes dry matter per hectare, worth up to €200 per tonne.

Financially, this is a difference of about €1,000 per hectare, or €400 per acre.

This amount would feed an extra cow per hectare.

Evidence at farm level indicates that there is a similar difference between paddocks on the same farm.

Researchers indicate that the main reason for the variation in production is the proportion of ryegrass in the swards. Of course, proper fertilisation and management, soil type, and drainage also have significant effects.

The main difference between pastures that are high and low in ryegrass arises in the early part of the year.

Teagasc research has shown that permanent pastures with low levels of perennial ryegrass are, on average, three tonnes of dry matter per hectare lower-yielding than perennial ryegrass-dominant swards, and 25% less responsive to nutrients — which means that 25% of fertilisers are wasted on bad pastures.

It is, therefore, recommended that pastures with less than 65% ryegrass are reseeded, if high production is required.

A Teagasc national survey has shown that 50% of farmers do some reseeding every year, while 25% never reseed.

Seventy-five percent of reseeding is carried out in the autumn.

Only 50% of farmers soil-test before reseeding, or use post-emergence spray to control seedling docks and other weeds, which, of course, limits the advantage of reseeding.

It is strongly recommended to reseed at least 10% of your farm every year; the actual figure achieved is less than 6%.

Timing of Reseeding

The main reason for reseeding in autumn is that there is a good supply of grass, which provides an opportunity to take out some areas for reseeding.

Farmers reseed too late in the autumn.

Early August (or April in the spring) are the ideal months.

A recent Teagasc experiment showed that with properly timed spring reseeding, the reseeded pasture produces as much grass as the old pasture in the year of reseeding, and is much better quality.

The turnaround time from spring reseeding to grazing is about 60 days.

Researchers say that spring reseeding gives much better post-sowing weed-control opportunities, and they recommend spring reseeding over autumn.

However, where docks and creeping weeds and grasses are a problem, early August reseeding provides a much better opportunity to control them.

Pre-spraying a silage crop in early August with a glyphosate spray, and cutting about 10 days later, gives excellent results, especially in controlling docks.

If sowing in early August, there should be ample opportunity for post-sowing weed control, and also a grazing before winter.

Check Areas to be Reseeded

A pasture check during the year will indicate areas of your grassland that are not producing satisfactorily.

You will notice that some paddocks are producing almost twice as much grass as others.

This may be due to some pastures having been damaged, or fertiliser/lime deficiency, or due to a low level of perennial ryegrass.

If a low level of perennial is the problem, there is little option but to reseed, if high production is required.

However, you must find out the reason for the low levels of ryegrass.

Reseeding Never More Important

Reseeding poor quality pasture has become more important than ever.

Farmers cannot afford to be buying unnecessarily large amounts of concentrates to supplement poor grass and silage, or to be applying expensive fertiliser on poor pastures that give a poor response.

The costs of concentrates are likely to go very high due to the unavailability of some maize by-products.

Reseeding is costly, but the cost could be recouped in less than two years, if the job is done correctly with good follow-up.

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