Topical technical for post post harvest weed control with Roundup
As harvest is progressing in most areas now is the time to plan the stubble cultivation regime to make the most of the ideal opportunity for maximising out of crop weed control with Roundup. With Black-grass dictating planting strategies for more farmers every year, delayed drilling has become an important part of integrated control. Decisions to plant the worst Black-grass fields last and carry out intensive stale seedbed glyphosate applications to reduce the seed bank before drilling can take significant pressure off in-crop herbicides.
Why use a modern Roundup?
High levels of efficacy, reliability in catchy weather and flexible label approvals can mean an extra chance at killing Black-grass compared with a generic glyphosate.
Modern Roundup brands: -
Are rainfast on annuals and Common Couch in just 1 hour. (Most generics 6-24 hrs)
Allow cultivations after only 6 hours. (Most generics 24 hrs)
Fully wetted. (Many generics require extra surfactant at the low rates).
Approved for use more than once in autumn stubbles. (Some generics can be applied only once)
Approved up to a maximum total dose of 1800g/ha in stubbles. (Many generics allow only 1440g/ha)
Approved for post-plant, pre-em use for a last flush if necessary. (Some generics are not)
Supported in tank mix with most pre-emergence residual herbicides. (Many generics have no supported tank mixes or only a restricted list)
Stale seed bed opportunity
Where rain follows combining and soils are moist a good Black-grass chit should be achieved from immediate cultivations. Remember to cultivate top down and consolidate with press/roll to conserve the moisture - Ideally cultivations should be shallow (5cm). Spray off annuals once they have 2-4 leaves with Roundup. Germination should take place in around 10 days provided there is sufficient moisture.
Where moist conditions prevail use the window between harvest and drilling for a double stale seed bed with a second cultivation after 6-24 hours and a further Roundup application to the next flush.
Delay cultivation If the soil is very dry with little rain forecast it may be best to wait as there will be losses through predation and weathering and the buried seed will not chit in dry soil. Optimum control of the following weeds is only achieved by not cultivating immediately: -
Volunteer oilseed rape - wait for the seeds to chit on the surface, (usually after 5mm of rain), to ensure buried seeds do not go dormant. Spray as soon as the majority have reached two leaves.
Perennial weeds like Common Couch, Onion Couch, Thistles and Volunteer potatoes can all be controlled when 10-15cm of re-growth is allowed in undisturbed stubbles.
Members of the Serrafalcus family of Bromes, (Meadow, Rye and Soft Brome) need four weeks of after-ripening on undisturbed stubbles before cultivating to encourage a good germination. With mixed grass weed populations choose the cultivation regime best suited to the most problematic species.
Post plant, pre-emergence – The final stale seedbed opportunity.
Tank mix a low rate of Roundup with the pre-emergence herbicide to tidy up the final flush just before the crop emerges.