Damaged swards: Can they recover?
Given the difficult ground conditions experienced on farms throughout the country, there are increased reports of sward damage. Many farmers are questioning the future production potential of these swards.
The effect of treading damage is dependent on the frequency and severity of the damage, as well as the sward and soil type. Swards with a high perennial ryegrass content, on well-drained soils, have the best resilience to intense treading.
Swards damaged in the spring produce much less dry matter (DM) than those damaged in the autumn, due to a reduced recovery period; but, where both autumn and spring treading events occur, annual DM production can be halved where severe damage occurs.
However, on better-drained soils, where damage wasn’t as severe or repeated, DM production will recover after the second grazing and has minimal impact on annual production.
Production can be reduced on damaged swards because of the destruction of perennial ryegrass tillers and increased soil compaction. Farmers need to assess damaged swards to see what line of action needs to be taken.
- The historical performance of the paddock;
- The level of perennial ryegrass;
- The severity of the damage to the soil;
- The severity of damage to the sward.
If damaged swards previously under-performed and had low perennial ryegrass content, they will be limited in their recovery because they are starting at a low base.
Productive swards with a high perennial content should recover relatively well from treading; provided the underlying soil is not overly compacted.
Paddocks with severe soil and sward damage will have compromised production and a complete reseed is the most reliable solution to correct soil damage and increase perennial ryegrass content.
Damaged swards which have severely reduced performance are a cost on the system and should be rejuvenated as early as possible in the spring, as they are unlikely to fill much of the feed budget over the coming weeks.
On less severely damaged soils, where compaction is not an issue, over-seeding may be an option to increase the perennial ryegrass content. Regardless of sowing method, soil-seed contact is essential for successful establishment.
It is recommended that tetraploid varieties be used for over-seeding, as they have a much larger seed than diploids and therefore have a better chance of soil contact. Tetraploid seed also has increased vigour for faster establishment to compete with the existing sward.
A sowing rate of 9kg/ac is typically used when over-seeding, along with 75kg/ac of 10-10-20. Over-seeded swards should be rolled lightly and, if possible, a light application of watery slurry applied (1,000-1,500 gallons/ac).
Frequent tight grazing of the existing sward should be carried for the remainder of the year to prevent shading and encourage tillering of the newly sown plants.
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