Reseeding is an important part of grassland management on any farm and is essential for maintaining productive grassland.
Given Ireland's grass-based system, it is one of the most important steps a farmer can take to maintain maximum productivity and profitability.
However, according to Teagasc figures, only around 250,000 to 320,000 acres of grassland is reseeded annually, which only equates to around 2pc of the country's grassland. This is very low, especially when compared to the UK, where an average of 12pc of grassland is reseeded every year.
Research has shown that increasing the proportion of the farm reseeded each year increases the amount of grass grown and utilised on the forage platform, resulting in increased farm net profit. According to the Teagasc reseeding manual, swards with low perennial ryegrass content are costing farmers up to €300/ha/year due to reduced DM production (they grow approximately 3t/DM/ha less annually) and reduced nitrogen (N) use efficiency.
Reseeding costs approximately €750/ha, however, the increased profitability of the new sward would cover the cost in just two years, making reseeding one of the most cost-effective on-farm investments.
Newly reseeded grassland also has a much-improved grass quality and hence feeding value. Teagasc Moorepark has found that reseeded swards give typically 8pc higher milk output per hectare.
With improved regrowth following grazing/cutting, reseeding grassland can be hugely beneficial to smaller farmers with less ground area to move animals too. High quality reseeds can carry more stock, increase live-weight gain, regrow faster, use nitrogen fertiliser more efficiently, begin growing earlier in the year and also grow later in the year. Reseeding also helps to improve silage quality.
With silage being the main feed on farms over the winter months, it is important to have the highest quality possible. Increasing silage DMD pc from 68pc to 72pc will reduce meal feeding by 1kg/head/day, according to Nicholas McKenna of Teagasc
It is also an effective method for reducing soil compaction, improving grass genetics with improved productivity, increasing durability and disease resistance.
Reseeding is like building a house, you have to have strong foundations. The foundations in this instance is the soil, specifically the soil fertility. Get the fertility right and it will thrive. Get it wrong and it will harm your margins.
The first stage of carrying out a reseed is to take soil samples from the area to be reseeded to assess your soils' phosphorus (P), potassium (K) and pH (lime requirement).
One soil sample should be taken from every 5ha planned for reseeding, the samples should be representative of the entire field/paddock.
Once soil test results are available, appropriate applications of P, K and lime can be made to ensure adequate soil fertility for perennial ryegrass germination, establishment and production. Maintaining the soil pH at the optimum level will increase the microbiological activity of the soil and result in better soil nutrient recycling and release.
Soil pH is also critical for maximising the availability of nutrients (N, P & K) applied in fertilisers. The optimum soil pH for grass growth is 6.2. To raise your soil's pH, lime is added.
It is preferable to apply to fields with very little grass cover and to avoid grazing or cutting until sufficient rainfall has occurred to wash the lime off the herbage.
For silage swards, apply lime before mid-March for the first cut or within one week after cutting on land being closed for a second cut, according to Teagasc.
Mind your Ps and Ks
Soil P and K are essential at reseeding time. P and K are required for rapid root and tiller development during the early stages of establishment. Also P & K is required to ensure the longevity of ryegrasses in the sward over time.
Aim to maintain soils at Soil Index 3 for maximum production and persistency of clovers and ryegrasses.
Apply P and K fertiliser as per soil test report and incorporate into the seedbed at sowing time (see below).
Insufficient soil P & K will result in the poor establishment of rye grasses/clovers and the benefits of reseeding will be lost.
While the cost of grass seed might only make up 20pc of reseeding costs, spending time deciding what varieties suit your system is important, especially considering most swards have a life span of up to 10 years, according to Teagasc.
Like picking a bull for breeding where no one bull has all the desired characteristics, the same is true for grass as no one grass variety will cater for every requirement, so it is important to pick a good, balanced seed mix that suits your farm and requirements.
When deciding to reseed, the most important thing to take into consideration is what the primary use of the sward will be.
You can then decide the most appropriate grass variety or varieties.
Currently, most reseeds are a mixture of diploid and tetraploid perennial ryegrasses.
Diploids and tetraploids both have different characteristics, so using a mixture of both can achieve a balance of desired traits, allowing for balanced growth throughout the season and minimise the risk of a crop seed failing. Use the Department of Agriculture's Recommended List and the Pasture Profit Index to identify suitable cultivars.
They evaluate cultivars across years and sites.
When picking a mix for grazing, you should use:
* varieties exhibiting high simulated grazing yields in recommended lists;
* high seasonal growth to extend the grazing season;
* varieties with high digestibility values;
* 35pc-50pc tetraploid varieties in mixtures on dry soils;
* 15pc-20pc of highly persistent tetraploids on heavy soils.
When picking a mix for silage, you should use:
* varieties which exhibit high silage yields in recommended lists;
* 40pc tetraploid (less on heavy soils);
* ensure the proximity of heading dates;
* avoid poorly persistent tetraploids.
White and red clovers provide a good source of protein in ruminant diets, both when grazed and conserved.
There is also the added benefit of nitrogen fixation by the clover plants, so less artificial nitrogen fertiliser is required for grass growth. White clover is a perennial legume.
The key to its survival and production potential is its multi-branched creeping stem (stolon), which provides sites for new leaves, roots and flowers.
The stolon stores carbohydrates and proteins, giving the plant the ability to over-winter and regenerate in spring.
Red clover is a short-lived perennial legume that typically lasts for two to four years. In contrast to white clover, it has an upright growth habit and a strong, deep taproot. Red clover is typically higher yielding than white.
Improvements in management and variety breeding have meant that with care, red clover can now be grazed by cattle without killing the plant.
Red clover can also be used as a break crop in mixed farming systems due to its ability to improve soil structure and nitrogen supply.
Big versus small
Large leaved white clover varieties tend to be higher yielding, but are less tolerant of grazing and compaction. If selecting varieties for cutting, choose large-leaved varieties for maximum yield.
If selecting for cattle grazing, choose medium leaf sizes and for sheep grazing, choose small-leaved varieties.