The main advantage of reseeding grassland on a farm is that, it will increase both the quantity and quality of grass grown.
Estimates vary but new reseeds should grow in the region of 20-40% more grass and importantly a lot of this growth will occur in the spring and autumn.
Also increased animal performance, improved responsiveness to Nitrogen and greater farm output are all important additional benefits.
However at roughly €300/acre it represents a significant investment, while also been without the field for between five to eight weeks.
Thus the importance of a successful reseed is vital.
Before spending money on reseeding any drainage issues have to be addressed first.
Drains should be cleaned and if shores are required they should be installed, where chips are been used the sub soil should be taken away as it has very poor fertility and poor drainage characteristics.
Ploughing can help with drainage and levelling badly damaged fields but be aware the ‘good soil’ with the high fertility is being buried and this may take some years to be built back up again.
As generally the rule, the earlier in the season reseeding is done the better. The reason for this is post seeding management, grazing off the sward and post spraying can be difficult once we get into late September.
A young grass plant is not very strong and will struggle badly with competition from other plants. Thus it is essential to spray off the old sward.
Any of the glyphosphate products are effective but rates need to be carefully checked as they can differ a lot.
Most of the products need between seven or more days to fully absorb the chemical. After the plant is dead the sward can be cut for silage or grazed.
Ensuring adequate Phosphorus (P), Potassium (K) and Lime are essential for successful reseeding. The most accurate way to judge a soils requirement for these is to do a soil test, but this can take two weeks so plan in advance.
If ploughing, wait until ground is ploughed to soil sample. If the soil is not being ploughed and a min-till method is been used, i.e. discing or power harrowing, lime will need to be applied to counteract the acid that will be produced as the old sward decays.
There are 2 options for liming:
- Traditional Quarry Lime – your soil test will give the application rate.
- Granlime – this can be spread with a fertiliser spreader its works very quickly but is expensive so is only suitable if smaller quantities are required.
As a general rule of thumb two to three bags of 10:10:20 per acre are required for reseeding but this will depend on the soil test results and if a farm is allowed to buy in P’s.
Some 2,000 – 3,000 gallons/acre of undiluted slurry has been used successfully to substitute for bag fertiliser.
Fine and Firm Seedbed
There is sometimes a lot of debate about to plough or using min-till. The decision will depend on a number of factors including cost, stoniness of ground, equipment available etc.
All the methods can give excellent results but the basic requirement does not change which is a fine firm seedbed.
After sowing the field should be rolled to ensure good soil to seed contact and preserve the moisture in the soil. If clover is important make sure this is on the surface.
Chickweed, red shank and docks commonly emerge after sowing. These should be sprayed if present with a suitable herbicide at the two to three leaf stage.
Pests like fruit fly and leather jackets can attack reseeding and should be sprayed early with a suitable pesticide.
These tend to be more of a problem when there is a lot of trash left on the surface, so good clean off before cultivations and trying to bury trash when cultivating are important.
Reseeding is an expensive investment which can deliver excellent returns.
However for the investment to succeed attention to detail and giving the young delicate grass plant every chance to establish is vital.
By Michael Donoghue, Teagasc Adviser, Galway/Clare Regional Unit