Is reseeding an option?

AFTER a period of drought with high soil moisture deficits and low grass growth, the idea of reseeding may be the last thing in some farmer’s minds.

However, given the excellent ground conditions at the moment, reseeding a poorly performing field on the farm may be an option this year.

Reseeding levels in Ireland are generally regarded as low ranging from 250,000 to 320,000 acres annually, or the equivalent of two per cent of our annual grassland area. As grass is our main feed during the grazing season and the primary source of winter forage is from grass silage, this low level of reseeding needs to be addressed.

Why would you reseed this year? We know from research trials that newly reseeded perennial rye-grass are up to 25 per cent more productive then old permanent pasture swards.

Reseeded swards are far more responsive to applied nutrients (N&P) and are more palatable to grazing livestock, resulting in higher intakes and subsequently higher productivity. The most noticeable difference in grass production between old and new swards is seen in the spring period, with much earlier grass growth. It is recommended that pastures with less than 40 per cent perennial rye-grass should be reseeded.

Most reseeding takes place in the autumn. However, some farmers are now opting to go with reseeding in the spring time but, whether it is autumn or spring, it generally takes a sward around 11 months to fully establish, so good grazing management in the early growth phase is very important in order to maximise grass production in the future.

Why this autumn might be a good year to reseed is because, in certain cases on heavier soil types, drainage and reseeding go together. Given the excellent ground conditions at the moment, getting land drainage works completed is manageable. The reason why you should drain before reseeding on wetter soils is that perennial rye-grass will struggle to persist in wet soils.

Wet soils combined with low soil fertility levels and silage harvesting will mean that you will not get the full return on your reseeding investment, as the perennial rye-grass will disappear from the sward after a few years. When you consider that reseeding will cost you as much as €300 per acre, you want to get the maximum return from this investment.

How fields are prepared for reseeding depends on a number of factors – that being the soil type, the amount of underlying stone and surface trash and, of course, the machine/contractor availability. A number of different cultivation and sowing methods are available, all of which are equally as effective once completed correctly.

The main methods are ploughing, disc and one-pass, and direct drill. By ploughing, one can sow seed with a onepass power harrow, or seed can be broadcast with a spreader.

The key points to note when preparing for reseeding are, have a soil test completed; spray off old sward, graze sward tightly or mow to minimise surface trash if not ploughing; apply lime to the ground; choose a cultivation method that suits your field; choose an appropriate grass seed variety based on the Pasture Profit Index (PPI), depending on what you want from the reseed i.e is it going to be grazing ground, silage or a combination. Once a field is limed, cultivated, and seed has been applied to a fine, firm seedbed, appropriate fertiliser should be broadcast, (24 units of Phosphorus and 40 units of Potassium K per acre on Index Three soils).

The choice of seed you use, like the cultivation technique, should be tailored to suit the field and the farming system and whether it is a grazing or silage mixture you require.

There is also the question of whether you should use a Tetraploid or a Diploid grass variety when reseeding; the percentage of each in the mix will be largely determined by soil type.

An extremely important part of reseeding is a post-emergence spray, which should not be forgotten when reseeding this autumn.

By applying this spray, you are tackling weeds such as docks, thistles and chickweed when they are at the seedling stage, and this is when they are most susceptible to spray and have a weak route structure.

Therefore, aim to spray reseeded sward before its first grazing at the two- to three-leaf stage. If you are planning on taking advantage of the excellent ground conditions at the moment for an autumn reseed, start the process now and aim to have seeds sown early to have the best chance of good establishment and a dense grass sward next spring!