Why you should reseed your pastures this autumn

The aim of autumn reseeding is to grow more grass and, through better utilisation, drive animal performance for cattle and sheep while reducing costs for purchased feed.

For example one can expect an 8pc higher milk output/ha. Due to the wet weather this summer many paddocks have been severely damaged by stock and machinery.

According to Adrian van Bysterveldt of Teagasc, Moorepark a single poaching event can reduce grass growth over a few months by a whopping 20 to 40 per cent. The more severe the poaching the greater the reduction in growth and the longer this will continue.

The selection of particular grass varieties for wetter paddocks is a useful option. Timothy is very tolerant to poaching damage but much more difficult to establish and requires different management than ryegrass pastures. Even within ryegrasses there is a great deal of variation.

Varieties that are very dense tillering are ideal for wetter paddocks as they provide more cover between the cow’s foot and the soil. They often are also slower growing in the winter and early spring and so require less grazing during the worst of the weather. However Tetraploid ryegrasses often result in more open pastures and often have improved autumn, winter and early spring growth. These varieties should only be sown on the driest paddocks so that the extra growth can actually be utilised.

Reseeding damaged paddocks

In cases of mild to moderate damage grass seed should be broadcast as soon as the ground has firmed up. The best time to do this may be just before the cows come to graze the paddock again. The cow’s feet push the seed into the ground and so it quickly germinates.

By the next grazing the new grass will be still too small to be eaten but will grow quickly. The addition of more grass seed will greatly reduce the weeds.

By the third grazing they will by a normal part of the sward. However after severe poaching paddocks need to be properly re-seeded, otherwise weeds will dominate and there will be much less quality grazing.

nResearch by Teagasc has shown that beef farms are producing approx. 6.4tonnes of dry matter (DM)/ha compared to 9.1 tonnes on dairy farms. So much more reseeding needs to take place if we are to make the best use of our grassland. Dairy farmers should reseed 10 – 15% of their farm annually and when selecting grass mixtures all farmers should differentiate between grazing and silage mixtures. In choosing a silage mix, go for a high overall DM production and density. For grazing one can combine three to four grasses of differing traits to obtain good seasonal DM production (spring/autumn) and high sward density.

Teagasc research shows that swards with a low proportion of perennial ryegrass are reducing profit per hectare by €300 due to reduced DM production. In general pastures with <65% perennial ryegrass should be reseeded. Recent research in Moorepark has shown old permanent pasture to be on average 3tonne DM/ha lower in DM production to swards that have 100% perennial ryegrass.

In a recent study pastures with 100% perennial ryegrass produced February growth rates of more than twice those of pastures with 40% perennial ryegrass. The annual improvement in profitability is worth over €200 per hectare. This coupled with the improved return on fertiliser should return the reseeding cost within two years. From late July to mid August is the ideal time to reseed. If you are planning to reseed this autumn then you should do so as early as possible. Later than this and you run the risk of cooler temperatures and swards that will be poorly established going into the winter. One should try and graze the new reseed at least once before the winter to encourage tillering. You also want to make sure that it will get a post-emergence spray for weed control in the autumn, which will be five to eight weeks after sowing.

nAt a cost of €200-300/acre you will want to maximise your returns from the reseed over the next 10 years. If soil fertility is poor then the sward will often revert back to the old natural grasses, so soil testing is vital to correct soil pH, phosphorus (P) and potassium (K) levels.


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