Teagasc has confirmed the role of post-harvest stubble management as a tool to try to control problem weeds, including herbicide-resistant grasses.
When deciding which fields to cultivate and to what end, a number of issues need to be considered.
Some weeds need light to break dormancy, e.g., oilseed rape (OSR) volunteers and wild oats. Others need to be buried, e.g., sterile brome and blackgrass.
It is a case of tailoring a strategy to deal with both options within the stubble cultivation rules.
These state that between 20 and 25% of the cereal area on the holding must be left untouched for ground-nesting birds.
So, it’s a case of picking the fields where the appropriate weeds will benefit from being left on the soil surface to be eaten by birds and small mammals.
Post-harvest stubble management
Stubble cultivation must take place within 10 days of straw being removed. However, exceptions are recognised. These include the growing of late-harvested crops are grown, e.g., maize, beet, potatoes and beans or if cereals are harvested after September 15.
In addition, if a winter cereal crop is to be sown before October 31, there is no need to stubble cultivate.
Shallow cultivation is only applicable to counties Carlow, Cork, Dublin, Kildare, Kilkenny, Laois, Louth, Meath, Offaly, Tipperary, Waterford, Westmeath, Wexford, and Wicklow.
Where cover crops are being established as part of the various schemes, these can be used to suppress the different weed species.
But they are also a good way of trapping residual nitrogen (N) in the soil and preventing it from reaching watercourses.
Growers should aim to sow cover crops as soon as the straw is removed, where possible. A week’s growth in August is worth two weeks in September.
The decision to bale or chop the straw should always be based on the economics of chopping the straw versus the price that can be achieved for baling the straw.
While individual deals will be done for the straw, its value as an organic manure can be calculated based on the total amount of phosphorus (P) and potassium (K) contained in the straw that is being returned to the soil.
Where straw is chopped, there are also the other benefits that are more difficult to calculate, such as the biological and physical improvements to the soil, especially where this has been done over a number of years.
Soil compaction could be a real issue in September-harvested fields, with heavy balers, loading shovels, bale trailers and possibly even trucks moving in all directions across the fields.