This has been a good summer and autumn for reseeding as there were very few drought periods.
Most of the reseeded pastures were burned off with a glyphosate product a few weeks before preparing the ground for reseeding.
But this only killed the old sward and existing growing weeds and had no effect on the millions of weed seeds lying in the top few inches of soil.
These weed seeds will germinate with the grass seeds and it is vitally important to spray the new reseeds before the weeds reach four inches high, because they are more easily killed at that stage.
This will usually be six to eight weeks after sowing.
Spray when the clover has at least one trifoliate and the grasses have at least one to three leaves.
Teagasc trials have shown that the financial rewards for spraying reseeds can last for over eight years if the swards are managed correctly.
If the reseeded ground did not receive a pre-reseeding glyphosate spray, and contained docks and other perennial weeds, the weed seedling emerging from the roots of these will only be temporarily killed by post-sowing sprays.
There are a minority of reseeds which may only contain a very low level of annual weeds such as chick weed, fat hen or red shank and these may not need spraying, because these weeds will not re grow after a good grazing or topping.
However, if these annual weeds are prevalent, especially chick weed, they should be sprayed, because they will leave blank areas into which weeds and poor grasses will grow.
The best way to keep weeds out of a new pasture is to maintain a vigorous well managed, well fertilised sward and this will enhance the effect of spraying.
Remember that if there are gaps in the sward they will be populated by undesirable species unless the good grasses are competing.
It is vital to keep a close watch on autumn reseeds for pests such as frit fly, slugs etc.
During the past few months, reseeding has been a major topic in discussion groups, open days and in agricultural articles.
Despite the relatively high cost of reseeding, it has been proved that these costs can be recovered in one to two years, if the reseeding and follow-up treatment are carried out successfully.
At this stage, autumn reseeding should be completed.
The main advantage of early autumn reseeding is that it usually provides an opportunity for a few grazings which will thicken up the sward.
It also provides opportunities for post-spraying and other necessary treatment. Early sown swards will also provide early high quality grass next season.
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