Managing grass surpluses

After a relatively slow start, grass growth has improved since mid-April, but remains below average for early spring in many parts of Northern Ireland. The GrassCheck project results also indicate that growth will soon be at its peak in most areas of Northern Ireland. However, unsettled weather conditions throughout April have resulted in some herds being re-housed either by night, or day and night, while other herds have still not been turned out at all. This will result in a surplus of grass on the grazing platform on these farms, with these surpluses likely to increase further given current and predicted growth rates.

To manage surpluses effectively it is essential that they firstly be identified, and this can only be done by assessing grass covers regularly. Targets for most herds at this time of the year should be an 18-21 day rotation, with cows grazing swards with grass covers of between 3,000 and 3,300 KG dry matter per hectare (third of the way up a wellington boot). If your cows are grazing swards that have covers that are higher than this, you will be forced to slow down the rotation, and this will lead to further grass surpluses. To keep rotation length and grass covers on target, skip the fields with the heaviest or ‘surplus’ covers as you are likely to achieve poor grass utilisation from these. The options to deal with this surplus grass include harvesting the grass for either clamp or round bale silage, or bringing additional stock onto the grazing platform to graze the surplus grass. Round baling has the advantage of being much more flexible compared to traditional silage harvesting, as smaller areas can be taken out of the rotation when necessary. Location of the fields, weather conditions and timing are all factors to consider when deciding on the most appropriate action.

Once a surplus is identified it is essential to react quickly.  Ideally these paddocks should be cut immediately to maintain their position in the grazing cycle and allowing them to be grazed next time round. One of the advantages of harvesting the surplus as silage is that grass regrowth starts almost immediately. However if fields with surplus grass are allowed to ‘bulk up’ before being cut, they will fall out of ‘sequence’, and in addition, recovery will be much slower following a heavier crop of grass. Thus a surplus can easily result in a deficit if not dealt with immediately. Alternatively, if dry stock are used to remove the surplus, care must be taken that they do not take too long, as this will also slow grass regrowth and limit supply for the next rotation.

Although removing surpluses is likely to require contractor assistance on most farms, failing to remove these surpluses will carry a much greater cost. Failing to remove excess grass will lead to poorer sward quality, lower grass growth, lower animal performance and a poorer response to applied nitrogen fertiliser throughout the rest of the 2009 grazing season. While 2009 contractor prices are not clearly defined at present, it is likely that round baling will cost around £6.50 per bale and silage cutting around £50-55 per acre.  Consideration must also be given to the appropriate storage of the resulting bales/clamped silage, and the disposal of waste plastic. However, this surplus grass, if cut at a young leafy stage, represents a high quality feed that can be fed back to the herd as a buffer feed during periods of unsettled weather or during grass deficit.

Only by assessing the grass supply on your grazing platform and checking that rotation length and pre/post grazing sward covers are on target, will surpluses be identified. Once identified, surpluses should be removed quickly to ensure that grass supply is not compromised for the next rotation. Although removing surpluses will incur a cost in most cases, this will be a small price to pay to ensure a continuing supply of quality grass for the dairy herd throughout the grazing season.

To maintain sward quality within the grazing area, grass surpluses must be identified and removed quickly.