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Dealing with heavy grass covers

29 March 2019
Type Media Article

By Mícheál Kelly, Teagasc Adviser, Galway/Clare Regional Unit

The spring of 2019 has presented many opportunities as well as challenges in terms of grass growth on farms. Given the above average temperatures we have seen, grass growth has gotten off to a flying start although it has been somewhat hampered by the recent cold, wet weather. Many farms are now facing the scenario of having more grass on the farm than they typically would at the beginning of April, with a low percentage of the overall farm grazed. There are many reasons for this but we must now take action to get grass back under control on farms.

  • Nitrogen Application – It sounds ironic to suggest spreading nitrogen on farms that already have a lot of grass but there is method to this madness. The nitrogen spread on a heavy grass cover is not necessarily for increased grass growth. The majority of the benefit to be seen from it is in terms of grass survival. Grass that has been growing over the winter may have used up what nitrogen was available in the ground, hence the yellowing effect we see in fields as the grass dies back. New perennial ryegrass varieties are especially dependent on nitrogen to keep their tillers alive. Where no nitrogen has been spread yet this spring, it is essential to get going with at least 30units/acre at this stage.
  • Silage Ground – For many, silage ground has not been grazed since the stock were removed from it last October. These fields will have seen good growth over the winter and due to poorer weather throughout March, this has not been grazed off. Where high quality silage is needed, these fields should be grazed out in blocks, using temporary fences to increase grass utilisation and achieve a good graze out. Fields should be grazed bare (3.5cm from ground) in the spring. Grass that has been growing since cattle were housed will have built up a lot of dead material at the butt. To put the importance of tight grazing in spring into context, over 80% of fresh leafy grass can be digested and used by the animal, whereas less than 50% of the mature stem and dead material content of a sward is of any benefit. Grazing to low levels in the spring will clean out this poorly digestible material and allow the grass plant to generate new highly digestible leaf material and additional tillers. The exception to this is where fields were grazed into the end of December. These fields will have higher quality grass on them and can be closed immediately as the period since they were last grazed is much shorter. In reality some of these heavy covers will be closed immediately for silage without being grazed. In this scenario the digestibility of the silage will be reduced but it can be cut earlier and brought back into the rotation quickly. Slurry should not be spread on heavy covers at this stage as it will stick to the leaf if we get warm weather without rain. It will however be important that the slurry is put back on these silage fields after the first cut has been removed. Where no slurry is being applied, a compound fertiliser should be used to replace offtakes.
  • Sward Damage - As farmers we are amazing in that we do not worry about keeping stock out of the sheds for as long as possible in the backend of the year but we hesitate to let them back out in the Spring. Yes, damage caused in the spring will slow down the growth in the next grazing rotation but spring grazing stimulates grass growth which increases the overall growth for the year, offsetting the effect of any damage. Damage to the sward in spring does not have as severe an impact as autumn damage as the daylight hours are on the increase and increased growth rates allow more tillers to repair any damage. Applying a compound fertiliser or slurry will supply the necessary phosphorus to the plant to repair its roots.
  • Grass Utilisation - It is easier to graze paddocks out completely without causing damage in a rotational grazing or paddock system. However, wire reels and pigtail posts can do a lot of work in improving the clean-out of larger fields on set-stocked farms. Reducing the grazing area will reduce the wastage of grass and prevent the grazing of any regrowth, which will slow down grass recovery.

A flexible management approach will be necessary to get grass back under control but with a little bit of care, we should be able to achieve 80%+ utilisation of this spring grass, dramatically reducing our costs of feeding.