Spring tips on getting a grip on grass growth

Commenting, Mhairi Dawson, R&D Manager at Barenbrug UK, said: “As the spring flush gathers momentum, and as grass cover builds, it can become difficult to keep an eye on quality – which can hamper any decision making left to the last minute. That’s why we are advising farmers to head out into the fields now. As a general rule, it’s good practice to walk your fields weekly from February to October to look at grass growth. But this is particularly important at the start of the season, where there is a relatively small window to influence pasture quality.

“In spring you need to look at your grass regularly to see how it’s growing and work out if any remedial work is required. You also need to keep a really close eye on leaf emergence rates as the weather warms up. What you see should dictate turn out times and decisions about grazing rotation length. Graze too early or too late, or get your grazing pressure wrong, and you run the risk of damaging your sward and suffering set backs with yields and nutritional quality later in the year.”

Knowing when to graze grass and for how long requires careful judgment. Barenbrug advises farmers to conduct regular visual checks of the number of tillers present on their grass plants to avoid problems. A ryegrass tiller will maintain up to three live leaves at any one time:

• The first leaf is the smallest and contributes approximately 25% of total growth
• The second leaf contributes another 35%
• While the third leaf is the biggest and makes up the remaining 40% of total growth
• Once a fourth leaf starts to grow, the first leaf will begin to die off

To maximise plant growth, grass quality, palatability and persistency, farmers should aim to graze between the second and third leaf stage, or earlier if canopy closure has occurred. However, when to graze grass and for how long will depend on the varieties or mixture used.

Graze too early, particularly on a new ley, and you can reduce grass growth and damage sward persistency; a plant’s reserves need time to restore themselves following growth.
Graze too late and the plant will enter the ceiling phase of grass growth. At this stage, tillers continue to produce new leaves, however, there is no further increase in net mass due to the dying off of older leaves. If the sward isn’t grazed at this point, dead material – with little feed value – will build up in the sward base. This in turn will affect the metabolized energy (ME) value of the sward; increase the risk of diseases such as crown rust; and decrease overall grass utilisation.

Concluding, Mhairi said: “Once you’ve decided when to graze and for how long, don't get complacent. Walk your fields at least once a week throughout the season. Swards conditions can change quickly depending on the weather and you may need to alter your plans and adjust your grazing pressure accordingly.”

If grazing pressure becomes too high, the result will be a short, stubbly sward, which will ultimately affect animal performance. With short grass, cattle are forced to consume all portions of the sward including poorer quality forage. This can lead to low animal intake and subsequently, low gains. Periods of excessively high grazing pressure can result in a decrease in overall sward production and can even put a field back into the lag phase – where regrowth is slow due to the plant’s sole reliance on its carbohydrate reserves.
If grazing pressure is too low, animal gains per head per day will typically be higher but production levels per acre will be poor. Put simply, low grazing pressure is likely to result in wasted forage. As with prolonged periods of high grazing pressure, extended phases of low grazing pressure can damage a sward, causing a loss of legumes from the stand.

To gauge grass quality and plan the best approach to grassland management, farmers have several tools at their disposal. One of the most common techniques is to make a visual assessment of the field in question. Other options include plate meters or sward sticks, which can be obtained from most major grass seed developers. When scrutinising sward quality, farmers should also routinely check for signs of compaction; measure pH levels; and look at the availability of essential nutrients.

The first year is critical

When dealing with a new sward, the young ley should be considered as ‘establishing’ for the first twelve months. The management of newly sown leys in this period is critical to achieving persistent grass growth. In the first year, many new grass crops will achieve high DM yields, even though the rooting structure is often poor. However, the long-term importance of the rooting structure should not be underestimated. Without strong roots, grass plants will be not be able to withstand future adverse conditions.

Generally – but not always – the more cover there is, the better established the grass sward. To check the status of a sward’s rooting structure, and gauge whether it is ready to graze, conducting a pluck test can be helpful. This simple technique will help determine if a plant is rooted well enough to prevent livestock pulling it out of the ground completely.

To conduct a pluck test, grasp the ryegrass seedling firmly between the thumb and forefinger, then tug in a single, quick movement – to mimic an animal biting. If the leaf breaks off and the roots stay in the ground, the pluck test is passed and the grass is ready to graze.

First grazing

When it comes to first grazing, it is important to remember that the aim – at least initially – is not about feeding your animals. It is about removing the tips of the plant to encourage new growth (tillering) and ensure any clover that is present has access to light and the opportunity to flourish. Under good conditions this will typically be at the six to eight month stage. In the first instance, try to use the lightest stock class available on the grass and leave stubble of four to five cms in length to allow the plants to recover faster.

For more information or if you spot a sward issue that you need help with, please contact one of the team.