Projecting the grass wedge using GrassCheck
A decision support tool is currently being developed combining information from the estimated grass wedge on the farm and predicted growth rates from GrassCheck.
The aim is to assist farmers with the projection of future surplus or deficits of grass within the grazing rotation, and help in the decision making process.
A practical on farm approach to this process is the concept of ‘grazing days ahead’.
Farmers who are experienced in grass budgeting can predict the grazing days ahead for a group of livestock by examining the grass wedge produced on their farm, determining the daily feed demand and incorporating growth information from GrassCheck.
Decisions can be made on whether to remove surplus grass from the grazing area based on the number of grazing days ahead of stock. For example during May, 10-12 days ahead is adequate, over 14 days will require remedial action to avoid a surplus.
Less than 10 days indicates an emerging scarcity, which requires one or more of the following options: slowing down the rotation; introducing supplementary feed; grazing some of the silage ground or reducing the stocking rate. As growth rates decline into the autumn time the target grazing days ahead of livestock should increase (25-30 days) to ensure sufficient grass is available.
Pre-grazing covers should also increase into the autumn to allow for a reduction in the quality of grass and the time spent grazing. If this is not possible then some concentrate supplementation may be necessary to maintain livestock performance.
Pre-grazing and post-grazing covers for different classes of livestock (Autumn)
| Pre-grazing KG DM/ha | Post-grazing KG Dm/ha | Available grass KG DM/ha | |
|---|---|---|---|
| Dairy | 3500 | 1600 | 1900 |
| Beef | 3500 | 1600 | 1900 |
| Grazing lambs | 2200 | 1700 | 500 |
Flexibility is key to any good grassland management plan, as changes are made throughout the grazing season to cater for periods of grass surplus and shortage.
This is made easier if the grazing area can integrate with the silage making area, which will provide grazing in both the early part of the season and in the back end when grass growth is slow.
Silage fields that are to be grazed early in the springtime should be closed off after being eaten down to approximately 1600 KG DM/ha.
Fields allocated for silage should not be grazed after the first week in April to avoid making stemmy silage.
