Summer Beef Series is in conjunction with Teagasc’s DairyBeef 500 campaign
Traditionally, most grassland reseeding takes place in the autumn (August/September), with about one third of reseeding occurring in late spring (April/May).
Autumn reseeding is the preferred option on many farms, due to reduced pressure on grass availability, increased availability of grazing ground after second-cut silage, and the threat of drought has subsided.
However, as autumn progresses, the weather can change quickly so timing is critical.
The aim for autumn reseeds is to have the ground reseeded before the first week in September. Delaying it until later on in September is risking having poor germination due to falling soil temperatures; deteriorating soil conditions making it more difficult to establish a firm seed bed as well as less opportunity to use a post emergence spray and get a grazing in before the winter.
Autumn reseeding
The target turnaround time for an autumn reseed should be 50-60 days. Therefore, farmers need to be picking the paddocks for reseeding and putting a grazing and spraying plan in place now.
If the grass seed is to be sown by the first week of September you can work back from this date. If discing or power harrowing, leave three weeks from spraying off until tilling the ground. For this to happen, you would need to spray with a glyphosate product before August 14.
If ploughing, it’s okay to sow 10 days after spraying so in this situation you would need to be spaying off before August 21.
A lot of surface thrash makes it more difficult to create a good seedbed; farmers need to be able to remove as much trash as possible through either grazing or cutting at least five days after spraying.
If removing thrash through grazing avoid spraying off covers above 1100kg/dry matter (DM) as getting livestock to graze covers above this will be difficult when sprayed.
Getting soil fertility correct is crucial if perennial ryegrass and clover is to establish well and persist after reseeding. Soil test for phosphorous (P), potassium (K) and pH (lime requirement) before reseeding.
If ploughing, take another soil sample six months later to check that soil fertility hasn’t changed significantly since ploughing.
Consult your advisor about a liming/fertiliser programme for the field to be reseeded that will bring the pH up to at least 6.3 (mineral soils) and the P and K indices up to soil index 3 and keep them there.
Grass seed mix
When selecting a grass seed mix for your farm use Pasture Profit Index (PPI) to identify suitable cultivars. The PPI is a variety selection tool used to identify the best varieties to sow when reseeding.
The PPI expresses the relative differences between varieties for agronomic traits such as spring, summer and autumn herbage yield, herbage quality, silage yield and grazing utilisation.
Seed mixtures that have varieties that are not on the PPI should not be used as these varieties failed to reach the minimum standard of performance.
For silage reseed mixes, choose varieties that score highly on the silage sub index however be mindful to keep the heading date range to about 6-7 days.
Reseeds that are destined for grazing should score highly on traits such as grazing utilisation, quality and spring and autumn herbage production. The number of varieties sown in a mix should be limited to a maximum of four, mixtures that contain many varieties can dilute the performance of the better varieties in a mix.
Combining diploids and tetraploids in a mixture will create a dense, high-quality sward however ensure you select cultivars which express high performance in the key traits on the PPI.
When selecting white clover cultivars to sow, use the Department of Agriculture, Food and the Marine’s (DAFM) Recommended List. Small and medium-leaved cultivars are best suited to intensive grazing systems, with large leaf clovers more suited to silage-based systems.
Sowing in the autumn can reduce chances of a successful establishment, as soil temperatures are on the decline, it is more difficult for clover to compete with the grass. Thus it is recommended that if you are planning on incorporating clover in the autumn, the earlier the better.
The use of white clover in grass mixtures has the potential to offset up to 150-200kg nitrogen (N)/ha as well as improving weight gains when cattle are at grass. In general, to establish a sward with >25% white clover, which is the level required for an animal production benefit, 1.5-2 kg/ac of white clover should be included in the seed mix.
Cultivation methods
How paddocks are prepared for reseeding depends on soil type, amount of underlying stone and machine/contractor availability.
There are four main different cultivation and sowing methods available. All methods, when completed correctly, are equally effective.
Do’s Do not’s Ploughing Shallow plough. Develop a fine, firm and level seedbed Plough too deep (>15cm). Cloddy, loose seedbed Discing Graze tight. 2-3 passes in angled directions. Apply lime Drive with fast forward speed – rough, uneven seedbed One-pass Graze tight, apply lime. Slow forward speed at cultivation Drive with fast forward speed – rough, patchy seedbed Direct drill Graze tight, apply lime and slug pellets. Wait for moist ground conditions (slight cut in ground) ‘Trashy’ seedbed – no seed/soil contact. Use when ground is dry and hard
Apply a post-emergence weed spray when the grass is at the 2-3 leaf stage; this is usually 5-6 weeks after sowing.
In the autumn, docks and chickweed are the two most critical weeds to control so make sure you use a spray that is effective against both these weeds. If clover is sown, make sure to use a clover safe spray.
It is important that autumn reseeds are grazed before the first winter. Graze the new reseed as soon as the plants do not pull out of the ground, approximately 700–1,000kg DM/ha. Calves or youngstock are a good option for the first grazing, particularly during poor grazing conditions
Catch up on other articles in the Summer Beef Series here.