Top tips for successful grass reseeding

To have a highly productive grassland farm, you must have high levels of perennial ryegrass in your swards.

Moorepark research tells us that on average old permanent pasture is producing 3t/DM/ha/year less than perennial ryegrass swards.

We really need to look at underperforming paddocks on farms. There is an economic loss of up to €300/ha in swards with a low proportion of perennial ryegrass.

Low-producing paddocks can be identified on farm by the number of grazings they get in the year. Fields grazed on average four to six times in a year need to be looked at.

Top-performing paddocks are those that have been grazed over 10 times in the year.

Old permanent pasture with low levels of ryegrass, along with a low overall production, will have particularly low early season growth. Regrowth will be slower, even in summer.

They will have a 25% poorer response to nutrients applied then a ryegrass sward and poorer grass quality and utilisation.

Timing

Timing will depend on current weather conditions and grass supply on farms. Autumn reseeding is most popular with farmers as demand from a feed budget point of view on farms is generally lower but has its challenges.

Lower soil temperatures and variable weather conditions reduce the chance to graze the new sward early whereas spring reseeding is a lot more flexible.

Turnaround time is where the biggest win is. The target turnaround time in which to get a reseed back into production should be 60 days.

Farmers are slow to reseed as they are afraid paddocks will be out of production for too long but old permanent pasture reseeded in spring with a short turnaround time can produce as many tonnes of DM/ha as previous years.

The first step in reseeding is to spray off old pasture with glyphosate. The main thing to target is beginning cultivation seven to 10 days after spraying off the old sward.

Soil fertility

Reseeding will improve productivity of a sward but soil fertility must be correct for it to have maximum effect. Test soil to find out the P, K and lime requirements before reseeding. The soil test will determine the level of fertiliser needed for perennial ryegrass germination, establishment and production.

If pH is not at the target of 6.3, reseeding is an ideal time to spread lime. Lime can be spread at a rate of 7.5t/ha (3t/ac) in a single application at reseeding. The decaying of the old sward can lead to acidity in the soil, so lime at reseeding is always recommend to counteract this, particularly if using minimum tillage techniques

Choosing the best variety to sow

Select varieties from the Irish recommended list. The pasture profit index (PPI) is a recommend list of varieties rating them on their seasonal production, quality, persistency, etc. The key point to know when choosing a grass mixture is the end use of the paddock – is it for a grazing or silage?

Know the type of land being sown – is it dry or wet land? And choose your varieties based on that. You want less than seven days’ range in heading date between varieties and there should be no more than three or four varieties in a mix.

Most of the co-op mixtures contain the top-rated varieties in the PPI and are adequate to sow and increase grass production on farms.

Seeds should be sown at a rate of 35kg/ha (14kg/ac).

Cultivation techniques will differ from farm to farm and even from paddock to paddock. Choose a cultivation technique or sowing method that suits your farm or particular paddock. Once everything is done correctly, there is little difference between the methods.

The four main methods are ploughing, discing, one-pass and direct drill:

1 Ploughing: ploughing is the best method to use when field surfaces are uneven and need to be levelled.

When ploughing, the main thing is to avoid ploughing too deep (more than 15cm) as this can bury the top layer of soil, which is the most fertile.

Aim to develop a fine, firm and level seedbed – the use of a land leveller will help generate this.

If the seedbed is cloddy and loose, grass seed will be buried too deep and will not germinate.

2 Discing: discing and a one-pass system is as good a method as ploughing and maybe the preferred option where only minimum tillage is needed.

The main thing to remember when discing is to graze tight beforehand and aim to disc-harrow the field two to three times in angled directions to break the sod and turn up enough soil to form a seedbed.

3 One-pass system: a one-pass system can often leave you with rough and patchy swards.

The main thing is to maintain a slow forward speed at cultivation to ensure a better finish.

4 Direct drilling: direct drilling is probably leaves the most variable of results as it is difficult for seeds to establish as there is no cultivation of the soil. It is not suited to very dry, hard ground.

Again, grazing tight beforehand is essential. Apply lime if needed and also slug pellets are advisable when using this method.

Ideally, wait for moist ground conditions, spread your fertiliser and direct drill the seed.

Management of reseeded swards

It takes a new reseed 11 months to fully establish and management in this period is very important. In the first eight weeks, you need to spray the weeds, get nitrogen and P and K out and graze the paddock.

You are aiming to graze the paddock when grass is at the two-leaf stage around 700kg to 1,000kg DM/ha.

Avoid grazing high covers of more than 1,200kg DM/ha and don’t harvest for silage. Try to graze the field with calves or young stock the first time to minimise damage, if possible.

From the second grazing onwards, graze the field at 1,000kg to 1,400kg DM/ha. Avoid poaching the field.

Graze the field tight to encourage tillering, which will lead to a denser sward establishing and try not to cut for silage in the first year.

Fertiliser

Lime and P and K fertiliser rates depend on soil test results.

The most common fertiliser used at reseeding is generally three bags of 10:10:20 per acre, which meets requirements for good root and tiller development in index 3 soils for P and K.

Nitrogen is essential for good grass establishment.

Grass seeds have a low N requirement during the early stages of growth, so be careful not to go with too much early on as it can promote the growth of weeds.

Apply approximately 40kg to 75kgN/ha at sowing and another 40kgN/ha four to six weeks after sowing.

Weeds are best controlled at the two- to three-leaf stage. Chickweed and docks are the two most critical weeds to control in a new reseed.

An application of a herbicide spray at this stage will usually be good enough to control them. Herbicide choice is important as you need to target the particular weed problem you may have.

Talking to your local adviser or merchant representative at this stage would be advisable. If clover is sown, use a clover safe spray.

Pests can also cause a problem around reseeding, with frit fly, leatherjackets and slugs being the most common.