Guide to Reseeding
We have put together a comprehensive to re-seeding that we hope should cover any questions you might have. In the event that you require further information please Contact us for help.
Reseeding should be given strong consideration when any of the following features become evident in a sward:
- High content of weed grasses, e.g. Scutch, Bent Grass.
- Low ryegrass content.
- High content of broad-leaved weeds, e.g. Chickweed, Docks, Thistles and Buttercups.
- Reduced milk yield or Liveweight gain.
- Poor re-growth following grazing or cutting.
- Bare patches throughout sward.
- Reduced silage DMD values.
In general, swards cut twice for silage annually should be reseeded every 5-8 years. For grazed swards, the arguments for reseeding on a regular basis lie in the areas of extended grazing season, improved re-growth and the continual improvement in yield and quality achieved by the breeding of new rye-grass varieties.
Swards can be reseeded any time between April and October, provided weather conditions are conducive to good emergence and establishment. Grass seeds have small energy reserves which means seedlings will not survive long in periods of cold weather or drought. Germination and establishment improve dramatically once temperatures rise above 10-12 degrees centigrade. Moisture availability is extremely important and reseeding during mid-summer may be problematic for this reason. Timing of sowing clover is even more important. To guarantee good germination and establishment clover should be sown by the end of August at the latest.
When reseeding in Autumn, direct sowing of grass seed is the only option available. In Spring, however, as well as sowing directly, grass seed may be undersown to either a cereal crop or to arable silage. Both of these methods offer attractive advantages, such as provision of a second crop and claiming arable aid which reduces the cost of reseeding.
There are different methodologies of sowing grass seeds available. In Ireland, however, the vast majority of reseeding is carried out by the conventional method of 'plough, till and sow'. This is without doubt the most certain and consistent method of establishing a vigorous and healthy sward. It is also the most expensive, but, as most swards are laid down for a period of several years, the cost should be regarded on a per annum basis, rather than as a once off payment. Other methods of reseeding such as direct seeding and slurry seeding have a place in certain circumstances and cost may be lower. However, no other method offers the same reliability of establishment and longevity of persistence as sloughing, tilling and sowing.
1. SWARD DESICCATION PRE-PLOUGHING
Spraying with glyphosate (Roundup, Gallup, Touchdown, etc.) before ploughing is strongly advised. It removes weeds such as scutch and bent grass, docks, thistles, etc. It provides for easier ploughing and tilling, resulting in less cloddy seedbeds.
Important points in relation to glyphosate spraying are:
- Ensure adequate sward cover present (10-15 cm regrowth).
- Good growing conditions are essential.
- Different formulations are available - check label.
- Use sufficiently high rate to kill strong weeds, e.g. Docks.
- Do not use contaminated water from rivers, streams, lakes.
2. FERTILITY MAINTENANCE/IMPROVEMENT
The use of a soil test to determine soil fertility is strongly recommended. If lime is required, it should be applied pre-sowing and worked into the top 10-15 cm of soil. In the absence of a soil test, a basic dressing of 3-4 bags/acre of a balanced fertiliser such as 10.10.20 should be applied at sowing.
With regard to undersown crops, the fertiliser application should be tailored to the requirements of the arable crop.
3. SEEDBED PREPARATION
Good ploughing is essential to minimise competition from the old sward. Adequate tilling and rolling, both before and after sowing, are necessary to produce a fine^ firm seedbed. This will ensure:
- Good contact between soil and seed.
- Moisture is conserved in the soil.
- A level field will result.
4. POST-SOWING MANAGEMENT
Reseeded swards are particularly vulnerable to damage from pests and weeds during early establishment. Careful monitoring of swards is essential with appropriate action taken, where necessary.
(a) Pest Control
(i) Slugs - These may be a problem in wet areas and/or wet years. Using baits will help indicate potential problems. If significant damage is visible or is likely, apply slug pellets to the soil surface.
(ii) Leather jackets - these may cause problems particularly in Spring-sown swards following grass. Seedlings are severed at ground level. Chemical control using Chlorpyrifos (Durs-ban/Clinch) is warranted if damage is noted or high populations of leatherjackets are seen.
(iii) Frit fly - this is generally the most common pest of reseeded" swards. The adult fly lays eggs on the soil surface and the white larvae which emerge burrow into the young grass shoot. The growing point is killed and the seedling turns yellow. Swards, following grass or grassy stubble are most at risk. Chemical control options include Dursban, Clinch and Decis.
(b) Weed Control
In new swards it is important to control weeds at the early seedling stage. Excessive competition from weeds will result in patchy swards. Furthermore, as weeds like docks and thistles get older they establish strong roots which make them more difficult to control. Any reseeded sward will contain a bank of weed seeds which germinate when the soil is disturbed. Glyphosate spraying pre-ploughing will only control established weeds and has no effect on ungerminated seeds.
Weeds such as Fat Hen (Lambs Quarter), Redshank and Hempnettle will be controlled by grazing and/or topping, provided populations are relatively low.
With high numbers of these weeds however, and the presence of problem weeds such as docks, thistles, chickweed and cleavers, chemical control will be needed. The choice of product will depend on the importance or otherwise of clover and the weed spectrum present:
(i) Clover Unimportant - Use CMPP or CMPP-P (various products available). These will control seedling docks, chickweed, cleavers and charlock among others. MCPA will provide the cheapest control of thistles.
(ii) Clover Important - Use 'clover-friendly' products such as Legumex Extra, Legumex DB, Nintex, Alistell or branded 'under-sown' products. Individual products carry certain limitations regarding particular weeds, so always check the label for effective use.
(c) Sward Management
Reseeded swards will tiller better and subsequently be denser in nature if grazed a few times after emergence. Poaching of new swards should be avoided. Even in silage swards, grazing at intervals will improve productivity and help to prolong the life of the sward. With undersown swards, a dressing of fertiliser high in P and K following removal of the arable crop, will help to promote vigour in the sward.