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 glysophate product a few weeks before preparing the ground for reseeding.
But this only killed the old sward and the growing weeds, and had no effect on the millions of weed seeds lying in the top few inches of soil.
These weed seeds 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, which 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 glysophate spray, and contained docks and other perennial weeds, the weed seedlings emerging from the roots of these will only be temporary killed by sprays after sowing.
A minority of reseeds 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 regrow after a good grazing or topping.
However, if these annual weeds are prevalent, especially chick weed, they should be sprayed, or 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.
The cost of reseeding is high but also highly rewarding if the job is done right and pre and post sowing spraying is carried out properly.
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