Your Guide to Overseeding this Spring

Overseeding is a very simple but effective way to rejuvenate old or damaged grass leys without the cost of a complete reseed. Increases in yield and quality can be achieved without ploughing and the time spent out of production can be reduced.

Recent trials have seen results from over seeding into an existing ley by:

  • An increase of yield by over three tonnes of dry matter per hectare
  • Increases in D value by two points
  • Higher crude protein; metabolisable energy, and sugar contents

When & Where
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. Good seed to soil contact is vital when over seeding. Timing is imperative and the main aim is to minimise competition from the existing sward. The best time to over seed is March, April, July or September as the grasses are not growing as vigorously as they are in May and June.

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 mole hills 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 over seeding grass seed mixture by speaking to a Wynnstay specialist 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). The following year you can continue with normal grassland farming.

Fertiliser Requirements
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, and ensure phosphate and potash levels are above a soil index of 2. 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.

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