Most farmers choose to reseed grassland during spring and ground conditions are currently ideal for working soils.

Reseeding older swards or under-performing paddocks should be an annual occurrence and part of a good grassland programme.

There is little point applying large volumes of fertiliser to older swards that are slow to respond to nitrogen.

More often than not, it is the lack of growth on older swards that leaves farms tight for grass at various points of the year. Outlined are some question farmers commonly ask before reseeding grassland.

1 Which paddocks should I choose to reseed?

When deciding on which fields to reseed, there are a few things to consider. First is how quickly does the sward regrow after stock have been moved off it?

After grazing, productive swards dressed with 20 to 30 units/acre of nitrogen should be ready to graze again after a rest period of 14 to 21 days during spring and summer.

Another factor to look at is the level of perennial ryegrass in the sward

If swards are taking longer, then these fields should be marked for reseeding.

Another factor to look at is the level of perennial ryegrass in the sward. Ryegrass will respond best to nitrogen. Natural grasses such as fescues and meadow grass have limited growth potential.

Once perennial ryegrass content falls below 50% of the sward, it is well worth taking these paddocks out for reseeding.

2 Will reseeding alone increase grass growth?

Just because a sward has been reseeded does not mean grass growth will automatically increase. A field may have limited growth because of low soil pH, low soil fertility, soil compaction and poor drainage.

Therefore, it is worth taking the time to address these issues first before going to the expense of reseeding.

3 Is ploughing the best option for reseeding?

For fields with compaction or drainage problems, ploughing is recommended, especially after installing new drains. Ploughing opens up soils, improving aeration and natural drainage.

However, the downside with ploughing is that is leaves a softer seed bed compared to stitching-in methods.

Rolling after drilling grass seed can tighten the seed bed, shortening the time lag

This means there is a longer time lag from when grass seed is sown until cattle can start grazing the new sward. Rolling after drilling grass seed can tighten the seed bed, shortening the time lag.

Ploughing also disturbs the seed bed, resulting in higher levels of weeds in new swards compared to stitching methods. Therefore post-emergence sprays may be required.

Finally, on farms where fields are rarely reseeded, ploughing turns the good soil down into the ground, while bringing up poorer-quality soil for a seed bed.

4 What are the advantages of stitching grass into an old sward?

Stitching grass seed into an existing sward has multiple benefits. Firstly, it is usually cheaper. It is also quicker to complete.

The seed bed is firmer, meaning the new sward has greater stock-carrying capacity and there tends to be fewer problems with weeds.

However, it has limitations. Stitching grass seed does nothing to improve soil aeration or drainage, so it is advisable to consider carrying out such work beforehand.

As the old grass dies off, it makes the seed bed acidic

Ideally, the older sward should be burned off first to give new grass a better chance to establish. Discing the field will create more tilth, meaning better seed to soil contact.

As the old grass dies off, it makes the seed bed acidic. Therefore, spreading lime beforehand will improve germination.

After stitching, it is important to graze the reseed frequently. This cuts down regrowth of older grasses and encourages new grass to tiller out.

5 What type of grass seed should I go for?

There are plenty of options for grass mixes, so make sure you choose the most appropriate to suit soil type and the purpose of the sward.

Pay attention to heading out dates

Tetraploids grow tall and erect, making them ideally suited for silage swards. Diploids are better suited to grazing as they tiller out better. But there is a happy medium between both. Pay attention to heading out dates also.

6 Should I take soil samples before reseeding?

Normally the advice would be to take soil samples before reseeding. However, where cattle are currently grazing paddocks marked for reseeding, or fertiliser has been recently applied, soil sampling now will not give an accurate picture of fertility.

That said, it is still a good idea to apply lime. Phosphate (P) and potash (K) is recommended to get seeds germinated.

7 Is a post-emergence spray needed?

Weeds can be quick to establish in a spring reseed, so a post-emergence spray will hit docks, chickweed, red shank, etc.

The alternative is to plough and till the field and leave fallow for 10 to 12 days before sowing grass seed. This way, the weeds will germinate first and can then be burned off.

Grass seed can be sown out afterwards. While this is a slower method of reseeding, it is an option where the aim is to get high levels of clover established.

8 Should I graze the reseed or take a light cut of silage?

Ideally, you should aim to graze the reseed in its first year to encourage tillering. Also, there is less chance of damaging the new sward from heavy machinery.

If you do have to cut silage, go with a light and often approach to replicate grazing. Do not opt for bulk.

9 How soon can I graze a reseed?

A quick test to determine when a new sward is ready for grazing is to grab a few plants between the thumb and index finger, then pull with light to moderate pressure. If the seedlings pull up from the soil, the sward is not ready to graze. If the seedlings remain in the soil, the sward can be grazed.

Best practice is to graze hard and fast for three to four days, then fertilise

Start with light cattle such as autumn calves of yearling stores. Sheep are also ideal, but be careful not to over-graze.

Best practice is to graze hard and fast for three to four days, then fertilise and allow the sward to rest for three weeks. Use electric fencing to protect grazed areas.

10 Should I target a reseed with more fertiliser?

New grass will respond better to nitrogen, so target more nitrogen to younger swards to drive grass growth. On a new sward, opt for a compound NPK with added sulphur. Applying P (phosphate) will help the new grass plants establish roots, while K (potash) will help with nutrient uptake.

Read more

In pictures: an inside look at breeding 2020 on Tullamore Farm

Beef management: five tasks to improve grazing swards