Rainfall over the last 10 days has rejuvenated the grass plant once again. Moisture deficits certainly were not anywhere near critical levels just yet, but there is no denying that grass was beginning to feel the pinch – reseeds included.

Most parts of the country have received a nice drop of rain by now and growth rates are the better for it. So too are reseeded swards which appear to have really sprung to life over the last 10 days, much to the relief of those who sowed grass seed.

Spring reseeds

Those who reseed in the spring are in the minority. Most reseeding in Ireland takes place in the autumn, primarily because more land tends to be free later on in the grazing season.

The good news for people that reseed in the spring is research carried out by Teagasc shows that, in spring reseeds, there is virtually no difference in grass DM production in the establishment year between the reseeded sward and an old permanent pasture sward.

This is driven by two factors: a shorter turnaround time (versus autumn) and the new sward is back in production during the main grass growing season, thus allowing for a number of grazings to take place in the establishment year.

Interestingly though, research also shows that it takes a full 11 months for a reseeded sward to become fully established.

So bearing this in mind, if we are to grow as much grass on our reseeded sward in year one as we would have on our old sward, management must be good. All the benefits of reseeding can be lost due to the incorrect management around the following:

Grazing

Turnaround time should be no longer than 60 days. The new grass is fit for grazing when the roots are adequately established to prevent the plant being pulled from the soil. Simply testing some grass plants by pulling with your fingers is a good indication. This is usually at a cover of about 700-1,000kg DM/ha (6-8cm).

Try to avoid grazing at anything higher than 1,400kg DM/ha (10cm) for the first time around. Letting new grass grow to this height will severely delay tillering.

Ideally, the first grazing should be carried out by light stock. Sheep are ideal but lighter calves or young stock will also suit. The main reason for this is to avoid poaching as the seedbed is likely to still be fragile.

After the first grazing, frequent grazing should be carried out at covers of less than 1,400kg DM/ha (10cm) and trying to leave as little of a residual as possible each time.

Reseeded swards should not be closed for silage in their first year of production as the shading effect of heavy covers will inhibit tillering of the grass, thus increasing the risk of an open sward in the second year.

Nutrients

Enough but not too much is the advice around nitrogen in the early days post-reseeding. Grass seeds have a low nitrogen (N) requirement during the early stages of establishment. Too much N will encourage weed growth and competition for new grass seedlings.

Approximately 40 to 75kg N/ha (32-60 units/ac) should have been applied at sowing time and another application of 30 to 40kg N/ha (24-32 units/ac) should be applied four to six weeks after reseeding.

Table 1 shows the recommended P and K application rates for grass establishment. The majority of this should have been applied prior to sowing but a top up may be required on low index soils.

During the final grazing, the sward should be grazed to as close to 4cm as possible and a light application of slurry is ideal.

Weeds

The problem with good growing weather is that weeds will excel just as grass does. Therefore it is important to keep a frequent eye on the sward to evaluate what stage grass and weeds are at.

The best time to control weeds is when they are at the seedling stage. This should always be before the first grazing, which usually corresponds to when grass is at the two- to three-leaf stage. Killing weeds at the seedling stage should result in a permanent kill.

The most frequently observed weeds in reseeded ground are usually docks and chickweed. However, other weeds such as charlock, redshank and mayweed can also be problematic.

In terms of herbicides, it is best to consult your local agricultural adviser or merchant, paying particular attention to the types of weed present and the types of grass present. Be mindful of clover. Pesticide users must comply with the Sustainable Use Directive (SUD).