Autumn management mustn't jeopardise minimum grass cover needed for spring
From a straight flush to going bust! Managing grass growth as we transitioned from August to September has been rather like a game of Blackjack. Many farm covers have changed from having massive increases to big losses, depending on where you're farming.
This has been very noticeable on free-draining soils where low rainfall levels have been coupled with a spell of colder weather.
These farmers are facing a challenge of extending the grazing rotation and building up grass cover. Not an ideal scenario if you are likely to go over quota – in this situation you really need to be able to produce milk from grass alone.
When faced with the undesirable, it's important to align decisions with the key priorities of autumn management. We extend the rotation length to extend the grazing season. But the key objective is to leave the farm fit for next season. This means leaving the farm with sufficient good quality pasture for the spring that will maximise grass growth for cows calving down in a condition score of greater than 3 (3.25-3.5 for heifers).
So autumn management must not jeopardise the minimum amount of grass cover required for the spring. In addition, it must avoid poaching, leaving poor residuals or excessively heavy covers that will impair grass growth in spring. Milking or underfeeding certain categories of cows for too long that results in thin in-calf cows is also a no-no.
On top of all these physical targets is the challenge of managing the risk of a super-levy fine on over-quota milk.
To illustrate, consider a 30ha farm milking 96cows at a stocking rate of 3.2LU/ha and currently producing 1.2kg of milk solids per cow per day. Let's say that this farm has 40,000l of quota remaining. When feeding 1kg meal per head the cows require around 15kg grass. So this would equate to a daily grass demand of 1,440kg drymatter (96 cows x 15kg). To work out the demand per hectare, we divide 1,440kg by 30ha to get 48kgDM/ha. In this situation the farm needs a growth rate of greater than 48kgDM/ha/day to increase the grass cover.
Say the farmer aimed to have an average pasture cover of 1,050kgDM/ha by September 30, and hoped to see this accumulate throughout September starting from an average cover of 825kgDM/ha on September 1 (825/3.2=258kgDM/LU). This would have required a grass growth rate of only 7.5kgDM/ha/day above pasture demand over a 30-day period or 55kgDM/ha/day, which is very plausible for the first half of September.