Keep eye on rotation when closing off covers
Published 12/10/2010 | 05:00
For most people, the beginning of the last rotation has started and a few paddocks should now have been closed for spring. Pasture covers have been built up during a reasonably favourable last month and should now be decreasing in line with your feed budget targets.
Having completed your feed budget, it is key that your management hits within 50kgDM/ha of your closing cover. Milking on and leaving a pasture cover which is substantially less than your budget target could expose a considerably bigger feeding bill in spring. With feed prices increasing, I would not consider this a wise move. November growth rates will generally not facilitate the accumulation of a significant amount of pasture cover, so if circumstances result in average pasture covers falling to 300kgDM/ha or less, irrespective of whether it's November 1, 15 or 30, this may mean that all grazing stock will need to be removed immediately from the grazing platform to protect covers for spring.
On the other hand, it is also quite possible to have too much pasture during the autumn closure period. Therefore, it's important that covers at this point are decreasing, so monitoring the pasture is still important. Covers of more than 1,800kgDM/ha should not be closed for spring, as these will suffer from winter burn and loss of quality. If these conditions become evident, you may need to graze on for longer than intended.
As I stated, extending out rotation length during autumn is crucial to facilitate grass being available throughout this month and into November. Targets have previously been suggested and, when put into practice, work similarly to a spring rotation plan in reverse.
An example is shown (in the table, above) for a 50ha farm, which starts the last rotation on October 6. Here, only 11.3ha is closed from October 1-15, even though 1.25ha is grazed a day because the area closed is not accumulated until October 6 (9 days x 1.25 = 11.3ha). Once October 15 is reached, the rotation is extended again to 45 days either by increased feeding, the use of a deferred paddock or by reducing demand. In this way, the target of 60pc closed by November 1 is achieved.
While this is a rather mathematical solution to a biological problem, which may not play out as planned, being aware of this and keeping an eye on your rotation may provide you with a simple tool that may indicate whether there is too little or too much feed being fed or pasture available.
For instance, consider the example outlined above. If substantially more than 11.3ha of the 50ha (or 23pc) has been grazed up to now (ie, second week of October), this would indicate that the rotation is too short and more feed or reduced demand -- by culling, drying off some cows or removing other stock -- will need to be considered. On the other hand, if substantially less than 11.3ha had been grazed, this indicates that the rotation is too long and there is too much feed on offer, so decreasing the supplements being feed, or by introducing or increasing another category of stock to help clean up paddocks, should be considered.
For many of us, this has been a fantastic year for grazing, and one hopes that mother nature is kind by providing us with favourable conditions to see out the remainder of the grazing year. However, a prolonged period of wet weather is still a potential challenge this autumn. Although, for many, grazing conditions are good, having received a substantial amount of rain over the past month, ground is not quite as able as it was to soak away this moisture.