Reseeding and spraying: Why and how can I get the best results?

Grazed grass is the cheapest source of energy for cattle and every blade that an animal eats represents a saving on feed costs and will have a positive impact on its liveweight gain.

Dairy calf-to-beef systems implementing high levels of grassland management – and maximising the length of the grazing season – have been shown to improve animal performance.

Speaking at a recent technical day – organised for the 14 beef farmers involved in the Teagasc Green Acres Calf to Beef Programme – Drummond’s Michael Slattery outlined the benefits of reseeding under-performing paddocks.

He said: “Under-performing paddocks are costing you money. Teagasc work has shown that the annual return on investment is less than a two-year payback when reseeding is carried out.

“So, it is one of the best things to do in terms of investing in your farm. You will increase the overall profitability of the farm which can lead to an increased stocking rate and improved animal performance.”

Michael highlighted that productive grassland farms must have perennial ryegrass-dominated swards.

“Old pastures are far less responsive to nutrients, so you could be putting out nitrogen (N) and you won’t be getting the kick out of it; new reseeds are very responsive to N. You also increase grass quality, with greater digestibility and better utilisation.”

He also noted that reseeded swards will result in better grass growth at the shoulders of the year – both in spring and autumn, which can lead to a longer grazing season.

How paddocks are prepared for reseeding depends on soil type, amount of underlying stone and machine/contractor availability.

There are many different cultivation and sowing methods available. All methods, when completed correctly, are equally effective.

Michael noted that farmers should: soil test; graze or mow tightly; spray; apply lime; decide on cultivation method; apply fertiliser; provide a fine, firm seed bed with good soil-seed contact; and roll after sowing.

“Reseeding costs €200-250/ac depending on technique used. Research from Teagasc Moorepark indicates that swards containing less than 65% perennial ryegrass should be reseeded and farmers should only use proven varieties when doing so.”

Benefits of reseeding:
  • Sward productivity increased 15-25%;
  • Higher stocking rate;
  • Better animal performance;
  • More responsive to N;
  • Better growth at shoulders – spring and autumn;
  • Increased number of days at grass;
  • Greater grass quality;
  • Greater feeding value;
  • Improved regrowth following grazing and cutting.

Concluding, he said: “You can get all reseeding done and get back in to graze it within 60-70 days. Paddocks reseeded in the spring do better and weed control tends to be easier too.”

In addition, Chris Maughen from TP Whelehan Crop Protection was on hand to discuss weed management in newly sown swards.

Commenting on the presence of docks in reseeded paddocks, he said: “When you disturb the soil, the seeds can last for up to 80 years and one dock can produce 80,000 dock seeds if let fully mature; there is more than likely millions of seeds in the soil.

“However, the important thing is to get in and eliminate those weeds before they get established and there are a range of newly sown lay products. If you can eliminate those docks before they get established, you will get a great result.

“Why? Because you are killing a seedling dock as opposed to a mature dock with a large root; it is much easier to kill a seedling dock with a small leaf. In two years’ time, a dock root could be a foot deep,” he added.

Chris also explained that the same tactics should be used when it comes to thistles – the earlier you spray this weed, the better the result. He also noted that farmers should walk the reseeded sward to inspect what weeds are present.

“Chickweed is another weed that can cause huge problems. What tends to happen is it will totally smoother out the grass, so there will be bear patches; other weeds will then occupy this space.

“It is really important to get chickweed early as well. There are two types – common chickweed and mouse-eared chickweed and there is a lot of the latter in newly sown and established lays this year,” Chris said.

Weeds in new reseeds are best controlled when the grass is at the two-to-three leaf stage.

“You’re looking at four-to-five weeks after you reseed; whatever is going to germinate will germinate with the grass; you don’t have to wait two months.

“If you can eliminate the weeds, grass will grow in its place. When you are trying to maximise your stocking rate, having weeds like docks can half the feed value.”

Chris also noted that the timing of the spray application – in established paddocks – is very important and, ideally, the dock should be hit when it is 8-10in in height or width.

“Docks will still die if they are bigger, but there’s a better chance of regrowth. Regrowth should be hit again within 12 months and there will be better long-term control; you don’t want to bring docks into the silage pit,” he added.

Teagasc research has indicated that a paddock capable of producing 10t DM/ha, with a 1t infestation of docks, will reduce yields of grass DM by 10%.

Therefore, a paddock with a 40% infestation of docks could result in a paddock growing 6t DM/ha and 4t DM/ha of docks – that’s a 40% reduction on the grass DM yield potential of that paddock.