Overseeding Grass Leys Guide

26 May 2022
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Overseeding is a simple but effective way to rejuvenate old or damaged grass leys, without the cost implications associated with a complete reseed. Overseeding can also be more efficient and reduces the amount of time that home-grown grass forage is out of production.

Timing is imperative with overseeding, and the main aim is to minimise competition from the existing sward. The best time to overseed is March, April, July or September as the grasses are not growing as vigorously as they are in May and June.

Site Selection and Timing

Overseeding is also best suited after hard grazing or close cutting.
Timing is imperative with overseeding and the main aim is to minimise competition from the existing sward
The best time to overseed is March, April, July or September as the grasses are not growing as vigorously as they are in May and June
Careful consideration needs to be given when choosing where to overseed, an open sward is needed, as a thick old "feggy" sward will be very hard to open out to allow the seeds to reach the soil
To get the best out of your ley make sure you check the pH, phosphate and potash levels of the soil
Apply lime if necessary to achieve 6.5 pH at a maximum of 5T/Ha (2T/Acre), split dress if more is required
Ensure phosphate and potash levels are above a soil index of 2

10 key points for drilling and seed Selection

Good seed to soil contact is vital when overseeding
Remove all grass by cutting or tight grazing
Scarify in at least two directions using a wire tine grass harrow
After this, if the sward is thin the seed can be broadcast on. It is then very important to tightly roll the field to get as much seed to soil contact as possible. It will also conserve moisture and flatten stone and molehills for silage ground. This is best achieved by using a ring roller or treading in with sheep (make sure the sheep come off after 7-10 days)
A method that is becoming increasingly popular is to slot seed into the soil, but you must be sure not to drill too deep
For both methods, tetraploid ryegrasses are recommended as they are a larger seed compared to diploids. They are used because of their strong, competitive growth habits, and are thought to have a higher drought tolerance compared to diploids
The grass should be sown at 10kg/Acre
Choose the appropriate Wynnstay stitching-in grass seed or contact the Seed Office for advice on which mixture suits your needs
You should leave the pasture for 5-6 weeks after sowing and then lightly graze
Make sure the root system is strong enough to withstand grazing, especially sheep, and that the animals are not pulling up the leaf blade and the root from the ground

Aftermath Care and Establishment

The following year you can continue with normal grassland farming. The new seedlings should be well established before Nitrogen is applied, this is normally around 4 weeks after sowing. If fertiliser is applied before this only the old grasses will benefit and out-compete the new ryegrass. The same method can be used for applying clover to swards. However, as clover is traditionally slower to establish we recommend you only sow clover in the summer or early autumn.