The overall average reseeding rate in the UK is somewhere between 2% and 4%, with grassland productivity estimated to be as low as 55% of potential, so the scope for gain is vast. Ideally a farm should be reseeding 15% of the grassland to improve productivity.
Silage and grazing fields should be inspected regularly to assess their condition. Inspect each field to assess which should be prioritised for reseeding. Look for the percentage sward content of productive ryegrasses and score the sward from one to five where one is the worst with <25% sown species and five is the best with >80% sown species, an even sward with very few weeds. A complete reseed costs an average of £900 per hectare (£360/acre) and the seed accounts for around £150 of this cost. The return on this investment will more than pay for the cost of the reseed in the first year in extra dry matter yield alone. Add to this the increase in quality of grazed grass and silage, and increased N use efficiency. The introduction of clovers into a sward is one way of reducing fertiliser applications. A 30-40% cover of white clover is required to see the real benefits of nitrogen fixation in grazing swards.
To establish grass seed properly, it pays to take time and do each step properly, as this is a period of investment to ensure performance and profit for the next 7 to 10 years. The most resilient swards that can go up against weeds, poaching, and adverse weather conditions, are the swards that are a dense and healthy population of sown species.
Grazing management
Knowing when to graze grass and for how long requires careful judgement and it is wise to conduct regular visual checks of the number of tillers present.
Grazing too early
On a new ley, grazing grass too early before a second new tiller leaf appears can damage grass persistency. If a plant’s reserves have not been fully restored, future growth will be in jeopardy. Repetitive early grazing can permanently decrease grassland yield and persistence.
Grazing too late
If grassland is left to grow too long (>3500 kg DM / ha) it will enter the ceiling phase of grassland growth. In this phase, tillers continue to produce new leaves, however, there is no further increase in net grassland mass due to the dying off of older leaves.
Adjusting grazing pressure
If grazing pressure becomes too high, it results in short grass stubble, which will ultimately affect animal performance. With short grass stubble, cattle are forced to consume all portions of grass including poorer quality forage. Periods of excessively high grazing pressure can result in a decrease in grass production. Grazing a field to a low residual, where there is too little grass left, can put it back into the lag phase – where regrowth is slow due to the plant’s sole reliance on its carbohydrate reserves. Where high grazing pressure needs to be relieved, the most effective option is to remove some animals from the grassland by allowing access to other fields.
Correcting low grazing pressure
With low grazing pressure, animals gain per head per day will typically be higher but production levels per hectare/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.
Short periods of high grazing pressure can be useful; one to two weeks of high grazing pressure, three or four times throughout the grazing season, can help maintain legumes in the stand and utilise forage that might otherwise be wasted. Other options for using up grass that’s not being grazed quickly enough might include round baling swards. This can bring the field back under control while creating a useful buffer feed for later in the season when grazing pressure may exceed grass growth. If fields are under grazed and growth gets ahead of the animals, topping with a rotary mower or topper to remove tall, rank vegetation and encourage new growth can also be helpful.
Thank you to Roger Bacon, Barenbrug Regional Manger.
