Reseeding can deliver big results within two years
The increased profitability of new swards makes reseeding one of the most cost-effective farm investments, writes Deirdre Hennessy
Less than 2pc of Ireland’s grassland area is reseeded annually despite grass being our dominant feed source Swards with low perennial ryegrass content are costing farmers up to €300/ha/year due to reduced DM production and reduced nitrogen (N) use efficiency.
And while reseeding costs approximately €750/ha, the increased profitability of the new sward would cover the cost in just two years making reseeding one of the most cost effective on-farm investments.
Recent Moorepark research shows that old permanent pasture produces, on average 3t DM/ha/year less than perennial ryegrass dominated swards. Old permanent pasture is up to 25pc less responsive to available nutrients such as nitrogen than perennial ryegrass dominated swards.
Reseeding will increase the overall productivity of the farm, allowing an increase in the stocking rate along with higher animal output – 8pc higher milk output per hectare relative to permanent pasture. It’s also an opportunity to increase grass quality, increase grass utilisation and allow white clover/perennial ryegrass pastures to establish as well as being more responsive to fertiliser.
The timing of reseeding depends to a large extent on weather conditions, and grass supply.
While autumn reseeding may make sense from a feed budget perspective, soil conditions deteriorate as autumn progresses; lower soil temperatures can reduce seed germination, and variable weather conditions reduce the opportunity to apply post-emergence spray and to graze the new sward.
Spring reseeding offers farmers greater flexibility. Swards reseeded in spring will have similar, or even greater, total herbage production in the year of reseeding compared to old permanent pasture.
Establishing white clover in a spring reseed is more reliable than in autumn due to the stability of soil temperatures in late spring, while post emergence spraying for weed control is usually very successful with spring reseeding due to favourable weather conditions in summer.
If ploughing use a shallow plough and avoid ploughing too deep (>15 cm) as this can bury the top layer of soil (the most fertile soil). Use a land leveller until an even seedbed is generated and aim to develop a fine, firm and level seedbed. If the seedbed is cloddy and loose, grass seed (and especially white clover seed) will be buried too deep and will not germinate.
Discing and One-pass
Aim for 2/3 passes of the disc harrow in angled directions to break the sod and turn up enough soil to form a seedbed. Forward speed must not be excessive as it can lead to rough, uneven seedbeds
With a one-pass system, the slower the forward speed of the machine the better in terms of finish. Often left rough and patchy due to operators moving too fast across fields.
Use a heavy disc harrow to do the primary cultivation followed by a final pass with a power harrow that can also be fitted with a seed box to till and sow with a ‘Onepass’.
Use shallow surface cultivation with a rotary power harrow to produce a seed bed with seed sown using an air seeder attached to the power harrow. Direct Drill
This can be a difficult environment for seeds to establish in as there is no cultivation of the soil.
A slight ‘cut’ in the ground will allow more seed/soil contact, although results can be variable. It’s not suitable on dry, hard ground and there may be a need to use slug pellets. It can also be more susceptible to scutch grass re-establishing.
Rolling is very important for both full reseeding and minimum cultivation to ensure seed to soil contact for seed germination.
Deirdre Hennessy is a grassland research officer at Teagasc Moorepark, Co Cork
Results: Reseeding will increase the overall productivity of the farm, allowing an increase in the stocking rate along with higher animal output