Role of cover crops
2018 cover crops grew well and can deliver large environmental benefits
Cover crops have grown exceptionally well in 2018, largely due to earlier than normal planting and higher than normal soil residual N levels.
As a result, cover crops in 2018 have the potential to deliver large environmental benefits in reducing nitrates loss.
Teagasc experiments have found that the response to nitrogen from cover crops, for the succeeding crop, is small, apart from leguminous crops. The challenge now is how to manage these crops to deliver maximum agronomic and environmental benefit to the farm.
Under the Green Low-carbon Agri-environment Scheme (GLAS), removal of cover crops is allowed after December 1. Management of cover crops depends on the species planted, available machinery and whether or not livestock are available.
Frost over winter will be enough to kill some species. The timing and methods used to remove cover crops will also be influenced by the succeeding crop.
Where a forage species has been used in the crop mixture, grazing with livestock is an ideal way to recycle nutrients, where the infrastructure is in place.
Where there is a large biomass present, the crop may need to be broken mechanically with a disc before ploughing. It is best to do this as soon after December 1 as possible, to allow the crop to degrade adequately to aid ploughing. Glyphosate will be the main method of destruction for most growers. The rate required depends on the species to be controlled, the level of biomass, and the weather conditions.
Key points to remember when applying glyphosate to cover crops are:
■ apply early in the day, to maximise uptake during short days;
■ application in cold conditions will slow uptake and symptoms will take four-to-five weeks to appear. Do not apply glyphosate in frosty conditions (frost-damaged crops will have poor uptake);
■ ensure accurate application, with the correct boom height, and use high water volumes (over 200 litres/ha); Where a direct drill is available, the cover crop can be sprayed off in the days prior to planting, and the succeeding crop planted directly into the cover crop.