Building grass supply through August and September does not happen by chance. A plan must be put in place to provide grass for cows as growth slows down. Essentially it is the simple relationship between growth (what is growing daily) and demand (what is eaten daily) which is fundamental to this plan.

As grass growth on project farms slows down during August, it will eventually fall below demand. Last week the average growth across project farms was 53kg DM/ha, while the average demand on project farms was 41kg/day.

Now we are in the first week of September, we only have another four to six weeks of good growth.

Naturally, the demand on project farms varies from farm to farm with herds at different stages of lactation, and differing stocking rates.

However, the ultimate goal on all project farms is to allow grass supply on the farm to build to its peak during August and September and allow the cows to eat into this supply thereafter.

Preparing an autumn grass budget simply ensures there is an adequate grass supply to feed the herd throughout the autumn.

Research from Moorepark Research Centre shows a benefit of €1.80/cow for every extra day grass is kept in the cow’s diet.

This benefit comes from less supplement feed required, a longer grazing season – which means the housing period is shorter, resulting in a lower cost with less labour and machinery required, and improved cow health associated with cows outside.

Nigel Corbett Banbridge, Co Down

This is the first year I have measured grass on the farm, and consider myself still at the early stages of development in grass management skills. Preparing an autumn grass budget is all new for me but, in simple terms, I am trying to stimulate growth and increase farm cover throughout August.

So far this year grazing conditions have been excellent on the farm, with the farm well head of target for grass growth, according to my Dairylink adviser Conail Keown. The grazing block has grown 8t DM/ha to date this year. Second-cut regrowth is now available on the farm for grazing.

Using this grass will help push up the average cover on the farm and extend the rotation length, which is currently 26 days. My aim is to build rotation length to 35 days by mid-September but keep rotation length under 40 days.

Demand is changing every week, with cows being dried off in batches according to calving date. These cows are still on the grazing block but will be coming off as they get closer to calving.

My target is to have 60% of the farm closed for the winter by 1 November, which means starting to close paddocks from the beginning of October.

The lower half of our grazing block can be heavy and wet in early spring, so some of the dry paddocks need to be closed first on the farm, to be available for early grazing next spring.

My average farm cover is ahead of target at 1,120kg/ha last week, mainly due to the second-cut regrowth included in the rotation. We are spreading 20 units of nitrogen after each paddock is grazed, and I will continue with this right up to the closed period, possibly reducing it to 15 units.

Soil fertility on the grazing block has improved, with phosphorus (P) and potassium (K) applied in the spring this year. Some lime is required on the grazing block and I am considering investing in lime rather than reseeding this year. Generally we reseed a paddock each year, but spending the money on lime would be a better investment. This is the first year I’ve budgeted, so it is a learning exercise and I am trying to be flexible in an attempt to see what works for this farm.

We are dependent on the weather conditions to supply grass growth, but demand is in our control. If farm cover is below target at any stage, we will take quick steps to bring it back on course – for example, by introducing a higher level of concentrate or removing dry cows. Equally if farm cover is above target then we’ll remove the surplus quickly as round bale silage.

During September and early October we will continue measuring grass supply weekly to monitor average cover. Once you know this, informed decisions can be made.