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Reseeding – Cost or investment?

August 17, 2022

It takes effort and expense to plan and manage an autumn reseed, but the return on that investment can be significant. Ciaran Hamill, College of Agriculture, Food and Rural Enterprise (CAFRE) Senior Beef and Sheep Adviser discusses the range of factors that impacts the level of return.

Reseeding will improve pasture quality, helping drive increased output. It will allow the use of newer, more nitrogen efficient grass varieties, making best us of any applied nitrogen (N), and allow for the introduction of clover, again helping to reduce overall N use.

Before deciding to reseed you need to do some work. There are a number of points to consider.

An autumn reseed will generally have less impact on the overall annual production than a spring reseed, due mostly to the seasonal grass growth pattern.

What is the existing sward composition and performance? Have you measured grass production and are you sure reseeding is the best option to improve grass growth? Is the field you plan to reseed the one on your farm that really needs action taken?

When was the last soil sample taken in the field and do you know the soil nutrient status? If you are in Zone 1 of the Soil Nutrient Health Scheme, you should take the opportunity to apply for soil sampling of all fields on your farm as soon as possible. It may be the case that addressing pH, P and K deficiencies and making better use of slurry and farmyard manure will improve performance. Reseeding alone will not correct soil nutrient management issues. Whether you reseed or not, addressing soil nutrient status issues will be a very good investment. If you do plan to reseed, then a soil sample and correcting any pH, P or K deficiency is a must.

If there is a significant weed burden, e.g., docks or thistles, spraying to reduce the burden may be worthwhile before going to a full reseed. This is especially true when looking at increasing clover content when post emergence spraying of the new sward will be restricted.

What is your current stocking rate? Do you have enough grass, and are you happy with animal performance? Reseeding will normally lead to an increase in grass production as the major return on investment. Can you utilise more grass effectively with your current stock and grazing system?

Have you examined the field soil structure? Are there any areas of compaction, or areas where drainage may have been compromised? Reseeding is a chance to do some remedial work on compaction and drainage, but other interventions such as mole ploughing or sward lifting could be beneficial before reseeding.

Is the field used primarily for grazing, silage or both? The recommended lists will show the best varieties of grass and clover to use in specific circumstances and all the major seed merchants have an excellent range of mixes to suit each situation. The best advice is to make sure that the varieties in your mix are all as far up as possible on the recommended lists available.

In the majority of cases, spraying the old sward to kill existing grasses and weeds is recommended. Ideally the sward should be grazed tightly and a short time allowed for recovery to give enough leaf for the spray to work, with the least amount of residual sward to decompose.

A traditional plough/power harrow/roll/seed/roll operation is considered the most reliable, and the most expensive. It will address any surface compaction issues but will also be slightly longer before grazing can restart.

Minimal tillage or direct drilling are good options where soil conditions are favourable and there is minimal existing sward to hinder seed-soil contact and seedling emergence.

When considering what varieties to sow there are plenty of options. The options include multispecies herbal mixes, ryegrass only mixes, inclusion of species such as fescues, timothy and cocksfoot for heavier soil types and ryegrass/clover mixes. Research by Teagasc on both dairy and sheep farms has shown that a grass + clover with significantly less N input can support a similar stocking rate and deliver a higher margin per hectare than a grass only sward with higher N input.

Consider all the factors mentioned above, as well as your own ability to manage grazing when deciding what mix to use. Introducing a paddock grazing system alone can increase grass production and utilisation. If you go to the expense of reseeding, then a good grazing system is key to realising the most from this investment.

When is the best time to sow? Grass and clover seeds need soil contact, moisture and warmth to germinate and thrive. What is the weather going to be like? Drought stricken or waterlogged soils are both detrimental to plant survival. After mid-September frost can start to impact soil temperature, plant germination and survival. Sow as soon as possible.

Post emergence management is very important. Control of weeds must be considered, and care taken to use the right spray if clover has been used in the mix. Light grazing, with young cattle or sheep if possible when seedlings have a good root structure developed will help plant tillering and ground cover. Do not overgraze.

Forage crops may be a short-term option on dryer fields that can be grazed over winter. Have you considered brassicas or another direct drilled forage for winter grazing, leading into an early spring reseed?

Making the decision to reseed requires a lot of effort, but with the right planning and careful execution, it will be a productive and profitable investment.