Overseeding: A flexible option to extend a sward’s productivity

Thursday 18.06.2020 , events , news

When looking to give an uplift to under-performing swards, or to correct any damage done to ground in the spring, sward rejuvenation is a worthy consideration. By overseeding or stitching-in, you improve the yield and quality of grassland whilst minimising any time out of production for the land concerned.

Overseeding grassland

Sward rejuvenation should be used selectively on swards noted to be deteriorating but yet still have a good proportion of perennial ryegrass present. Done correctly, and in the right circumstances, overseeding will enable you to get another few years’ out of the sward before a full reseed is necessary.

If the perennial ryegrass present makes up at least 50% of the grass species, then overseeding may well be a good way forward. Anything less than 50% and it is better to opt for a full reseed.

Overseeding is a tactic that is best used alongside a full reseeding plan. It is particularly useful to generate additional forage quickly and take pressure off when other leys are being completely renewed. In addition, it can cost effectively extend the life of a ley by two or three years, adding flexibility to a sward renewal programme.

Before overseeding, you also need to consider other factors, such as, broad leaf weed content and how much white clover is present.

If broad-leaf weeds, such as docks, thistles or nettles make up more than 15% of the ground cover, and white clover is not a significant part of the ley, then the decision to overseed could present a good opportunity to spray out the weeds. This cleans up the pasture and creates more space in the sward to overseed.

Best time to overseed pasture

You need to overseed when there is likely to be moisture, and with rainfall predicted, now could be a good time. Periods of drought or extended dry spells do pose a risk to any form of reseeding.

When overseeding you should ensure soil structure and nutrient status has been addressed as if not, these will need to be corrected before seeding.

Where possible, use a spade to dig a hole and ensure there is no compaction issues, test for pH, P and K and examine the results before you sow. It is essential to resolve any soil issues as these may be the reason the sward is underperforming in the first place, and if they are not rectified, the new seed will also underperform.

Ideally, overseeding should take place after a heavy cut of silage, or if after grazing, when the existing sward has been grazed down as tightly as possible. This is to reduce the competition from the existing sward for the new seedlings.

The two main options of overseeding are to stitch in the seeds or to scratch the surface and apply the seeds to the loosened soil with a grass harrow. Either way, the seeds need to make soil contact as if they fail to do this, they will not germinate. Therefore, ensure you do not sow the seeds into a thatch of grass and soil is visible.


  • Graze off the pasture to 3.5cm. If this is not possible, mow pasture down tightly
  • Use a guttler or stitch-in seeder across the pasture at a seeding rate of 8-10 kg/ac
  • Spread compound fertiliser (1.5-2 bags/ac) of 10:10:20
  • When stitching-in it is best to use slug pellets at the time of sowing, as the drills formed by the machine provide an ideal channel for slugs to move through and decimate the newly germinating seeds
  • Roll the pasture with a Cambridge or other light ring roller and apply a light coating of slurry (1,000-1,500 gallons/ac)

Grass harrow and fertiliser spreader combination

  • Ensure the pasture is grazed off well and clean to the base
  • Harrow with a grass harrow to ensure a levelling of the divots and disturbance of the soil surface
  • Spread grass seed (8-10 kg/ac) with a fertiliser spreader. The grass must make soil contact to have a chance of germinating and do not spread onto a sward which has a dense thatch of grass
  • Spread compound fertiliser (1-2 bags/ac) of 10:10:20
  • Roll pasture with a Cambridge roller or a light roller
  • Spread a light coating of slurry (1,000-1,500 gallons/acre) and ensure pasture is grazed frequently thereafter


  • Do not expect to see major differences within the pasture instantly, as it will take time for the new seeds to establish
  • Ensure the pasture is grazed at light covers to assist seedling germination and tillering
  • Overseeding will not work if seeding is followed by dry conditions so, ensure rain is in the forecast. If a dry spell occurs spread light levels of watery slurry (1,000-1,200 gallons/ac) or soiled water after grazing (this will only be a realistic option where small areas were overseeded)
  • These swards may require a post-emergence spray upon establishment
  • When correcting the soil nutient status, ensure to do so while following the Nitrates Directiveregulations for the land in question

Variety Choice

Ideally, use a high proportion of tetraploids, as these have a larger heavier seed and are likely to germinate quicker.

Germinal’s tetraploid grass seed mixture is specially designed for those looking for increased utilisation for intensive grazing systems, making it most suited for overseeding.

For advice on overseeding grassland, ask an expert from our grass and forage production team.


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