Taking steps to build autumn grass covers

Strong grass growth has been a common theme on many farms this year. On the programme farms, managing this growth has been a challenge, but the farmers have been both flexible and forward thinking in their approach to managing sward quality.

Grass growth is being measured on a weekly basis on the programme farms. When carried out properly and the information is used to base grazing decisions on, there will be significant improvements in grassland management.

The big advantage of grass measuring is that all grazing ground is walked once per week, not just the fields where livestock is currently grazing.

As a result, the farmers gain a better handle on which paddocks need fertiliser and which paddocks to skip in the next rotation because they have too much grass or ground is too soft to carry cattle.

It will also highlight which paddocks are slowest to recover from the last grazing and possibly need reseeding or have a compaction or soil fertility issue.

Once the farmers get confident with grass measuring, it becomes much easier to judge how many grazing days are ahead of cattle and when to take out paddocks of surplus grass for silage.

The end result is that cattle are consistently moving into swards of lush grass that drives milk production in cows and boosts liveweight gain in calves and store cattle.

Grass growth

Based on grass growth figures from the start of May to the end of July, grass growth across nine programme farms averaged 66kg DM/ha/day.

Total grass grown on the farms during this period is 5.4t DM/ha. Figure 1 outlines the average grass growth of the programme farms from May to July.

The range of grass growth on the individual farms is outlined in Table 1, with the highest daily grass growth on the farm of Mark Lewis in Co Armagh at 79kg DM/ha/day.

He is followed closely by Declan Rafferty and Aidan Quinn who farm at Pomeroy, Co Tyrone, and Ryan McDowell, who farms at Gleno, Co Antrim.

The geographical spread of these farms reflects just how good growing conditions have been this year.

Fertiliser application rates, soil fertility and having young productive swards also influence grass growth, as well as land type.

Fionbharr Hamill has the lowest grass growth from May to July, with 50kg DM/ha/day. The farm has lighter free-draining soils, but a lack of rainfall in June and July has hindered growth.

While daily growth rates may be lower, the farm will most likely have the longest grazing season across the whole year thanks to the dry nature of the soils.

Grazing demand

Stocking rates are high on the majority of farms. Mark Lewis is carrying 2,547kg liveweight/ha on grazing ground, which is just over 1,000kg liveweight/acre.

This would equate to one cow and calf unit per acre, or two forward store cattle. Declan Rafferty and Aidan Quinn are carrying a similar stocking rate of 2,530kg liveweight/ha.

Grazing demand is the amount of grass needed to grow each day to feed animals. Across the programme farms, grazing demand is currently highest on Declan Rafferty and Aidan Quinn’s farm at 62.7kg/day.

Grazing demand increases as the year progresses, as cattle become bigger and heavier.

In contrast, grass growth will start to fall from now until the end of the year. Growth rate tends to fall quickest on upland farms and those with heavier soils.

Therefore, the farms will soon be in a position where daily grass growth falls below cattle’s grazing demand.

At this point, farms can quickly run out of grass unless steps are taken to extend grazing days ahead to provide sufficient grass from August to October.

Target

The grazing rotation should ideally be around 21 days at the start of August. To extend the grazing season into late autumn, increase the length of the grazing rotation to 25 days by 1 September and around 30 days by the start of October.

This can be easier said than done. But with forward planning, good grazing management and discipline, it can be achieved.

Five steps to extending the grazing season

The obvious way to increase the grazing rotation is to bring in more ground.

Most farms will have second-cut silage harvested in August, giving additional acres for grazing. Fertilise this land as soon as it has been harvested with 25 to 30 units of nitrogen/acre.

Although grass growth will fall as August progresses, there is still an economic response to applying nitrogen fertiliser.

To boost growth rates, use a compound NPK fertiliser such as 25:5:5. You may also benefit from a higher growth response by using a fertiliser that contains sulphur rather than straight CAN.

Do not graze lactating cows on swards that have received high levels of potash in bag form or slurry and ensure they have access to magnesium supplementation.

Spring-born calves that weigh 250kg liveweight or more will be relying more on grazed grass, rather than milk from the cow.

Therefore, weaning these calves will greatly reduce the grazing demand of the cow.

Cows can be dried off and stocked tighter together as a sweeper group or put to rougher land if they are in good body condition.

Cull out empty cows at this point rather than allowing them to compete for limited grass supplies.

Cattle that will be finished this winter should be housed early for finishing.

This will relieve stocking pressure and grass demand, stretching grass supplies further into the autumn.

Using electric wire to control the grazing area will increase grass utilisation.

Strip grazing on one-day or two-day allocations will slow up grazing, preventing cattle from walking, trampling or soiling an entire paddock.

Using a back fence will also protect regrowth during August and September.