Establishment of multispecies swards
Many farmers may be establishing multispecies swards for the first time in 2023. These swards – which contain a mixture of grasses, herbs and legumes – offer a range of benefits, including: improved soil health; enhanced biodiversity; and increased livestock productivity.
When identifying fields for such swards, grazing paddocks are favoured over silage paddocks. Paddocks which are known to have a low weed burden must also be chosen.
As with all reseeds, soil fertility is critical to plant establishment and this is no different for multispecies swards. A soil pH of 6.2-6.5 is desired, while soil indexes of 3+ for both phosphorous (P) and potassium (K) are required.
Where inadequate levels of soil fertility are present, poor establishment will result and a direct reduction in the persistence of certain species will occur. Remember, areas that are lower yielding before reseeding due to poor nutrient status will still be lower-yielding after reseeding if the soil fertility issues are not addressed.
As the methods of weed control are limited with post-emergence when a multispecies sward is sown, weed issues must be addressed with herbicide before sowing.
Once multispecies swards have been established, no post-emergence spray can be applied to the whole field, as no chemistry is available that is safe to use on both the herbs and legumes included.
After reseeding, the only methods for weed control are either spot spraying, weed licking/wiping, mechanically picking/removing weeds or regular topping to reduce annual weeds. When opting for the chemical methods, use a spray that targets the most prevalent weed.
Despite the limited options available for weed control, when there is good establishment of multispecies swards, there is very strong evidence to show that they can strongly supress weeds. Although some annual weeds may occur after reseeding, these typically disappear after the first cutting/grazing and direct drilling results in lower weed emergence at establishment in comparison to ploughing/tilling/sowing methods of reseeding.
Methods of reseeding
Similar to grassland reseeding, the best conditions for sowing are without drought or frost and into a warm and moist seedbed (between April and August). Reseeds carried out in April and May will be favourable to the clover plants included, as appropriate grazing can be achieved without the risk of soil conditions deteriorating, which may be an issue with autumn-sown reseeds.
When establishing the sward, the plough/till/sow method or direct drilling may be used. Prior to establishment, spray-off the existing sward as per a normal reseed. Comply with the interval between spraying and grazing/cutting prescribed on the herbicide label, then cut the existing sward as tightly as possible.
Lime should be applied, if necessary, as per a normal reseed. If using minimum cultivation, apply 5t/ha of lime to the desiccated sward pre-cultivation. If ploughing, address any lime requirement post ploughing. Apply normal seedbed fertiliser at sowing (phosphorous, potassium and nitrogen) based on soil test results.
If the field has a history of weeds, prepare the field for sowing and then wait for the soil to green up. Consider the weed species present. If a post-cultivation, pre-sowing herbicide application is required to deal with problem weeds, spray with an authorised glyphosate product labelled for use in ground preparation, pre-sowing or pre-planting. Follow the herbicide label instructions set out for ground preparation, pre sowing or pre planting. If herbicide treatment is required at this stage aim to minimise soil disturbance between the second spraying and sowing while also following the herbicide label instructions.
Sow the multi-species seed mix at a rate of 12kg/acre (30kg/ha) at approximately 1cm deep (choose seeder carefully to avoid seed separation). Roll to get fine firm seedbed and good soil and seed contact. Allow six to eight weeks before the first grazing to let herbs establish strong taproots. Only graze if new plants are strong enough to withstand grazing.
For farmers who wish to oversow, the following advice should assist:
- Mix type - typically over-sow with seeds of herbs and N-fixing legumes (grass seed omitted as already in sward).
- Existing sward management - light competition from the existing sward will affect seedling growth, so over-sow after a tight grazing or after a silage cut;
- Seed rate – each species should be over sown with at least 2kg/ha of seed.
In terms of advantages, this method of establishment is cheaper and it takes fields out of production for a shorter period and offers better protection for soil carbon. When done correctly and with favourable conditions, it can be very successful.
However, this methods of establishment is less reliable than a full reseed. For the Department of Agriculture Multispecies Sward Measure, the grass component must be included as part of the see mix so oversowing will be a less relevant option.
After sowing, eight weeks must elapse before grazing to allow the herb’s taproots to develop. These swards should then be grazed to 4cm in the first grazing after reseeding to allow light to reach the base of the sward.
A maximum rate of between 80kg and 100kg nitrogen/year should be applied to multispecies swards with a good clover content of ~25% clover cover averaged over the whole year – clover cover is typically lower in the spring and increases over the year until about October.
This article was adapted for the Teagasc Signpost newsletter on sowing multispecies swards.
Also read: The multiple benefits of multispecies swards
Also read: Tips on establishing white clover in grassland swards