Move as little depth of soil as possible, give yourself enough time and use it to greatest effect. These are the three keys to the best, most consistent stale seedbed control of annual grass weeds ahead of drilling identified by independent tillage specialist, Steve Townsend.
“With good tillage management, 4-6 weeks between harvesting and drilling is quite enough time to get on top of problem grass weeds with two good pre-planting glyphosate treatments in most seasons,” he explained.
“Always see combining as your first cultivation. Leave a short stubble, avoid baling, chop straw consistently down to around 4” and spread both straw and chaff evenly over the full width of the combine to minimise the trash problems that get in the way of stale seedbed consolidation. Critically too, this will also maximise your soil moisture retention.
“Because soil moisture losses increase dramatically as soon as the crop canopy is removed, by cultivating within 48 hours of combining you will provide the best environment for weed seed germination.
“By cultivating only the top few inches you will further limit moisture loss while keeping the weed seed near the surface for rapid germination – even in apparently high dormancy seasons; always providing your consolidation is sufficient, that is.”
The most important tool in the stale seedbed armoury in Steve Townsend’s experience is undoubtedly the Cambridge ring roll. He stresses that this needs to employed within a day of cultivation to ensure the high level of soil contact essential for the rapid germination of small weed seeds.
He is adamant too that particular care should be taken to avoid excessive rolling speeds which limit consolidation effectiveness.
“Prompt early glyphosate spraying is equally vital,” he advised. “You should aim to spray-off emerging weeds at a single leaf. At this stage – between 7 and 14 days after cultivation in most cases – most fields will still look brown from the Landrover. So you need to get up close and personal with the ground.
“Then you should cultivate (if necessary) and consolidate the ground again as soon as product recommendations suggest so you can eliminate another flush of weed growth ahead of final seedbed preparation and drilling.
“Two stale seedbed cycles are invariably better than one, because the first weed seedlings to germinate secrete auxins which inhibit further seed germination. As well as cutting several days off the stale seedbed cycle, prompt treatment of the early germinators limits this inhibition. That way you get a further flush of weed growth – which would otherwise come through in the crop – stimulated and sprayed-off before you drill.”
Finally, Steve Townsend recommends drilling within a maximum of five days after the last stale seedbed cycle. Something that can best be ensured by using a glyphosate formulation with the shortest possible cultivation interval and by employing a high capacity cultivator or cultivator drill.
These essentials are especially important where short term cover crops are used, enabling the first weed flush to be sprayed off before they are planted and a further flush knocked out with the cover ahead of drilling.
“If good weed control is to be achieved without unnecessary delay to the main winter drilling schedule, glyphosate spraying must be managed as effectively as possible,” insisted Steve. “With a short autumn window between harvesting one crop and drilling the next on many units, poor or delayed weed control is simply not an option. Nor can hot and dry conditions, rainfall within a few hours of spraying or hard water conditions be allowed to compromise efficacy.
“This makes it important to use glyphosate formulations designed for challenging conditions rather than merely increasing rates and complementing them with specialist adjuvants or water conditioners wherever necessary in hard water areas.
“I recommend medium flat fan nozzles for optimum results on one-leaf grasses and water volumes of 100 litres/ha or less under normal conditions.
“Under dry conditions, you should spray early in the morning to optimise weed uptake,” he added. “And, of course, make sure you don’t exceed the statutory maximum dose on the label with multiple applications.
“Modern glyphosate formulations with approval for post-planting, pre-emergence application and good tank-mixing compatibility can be very valuable in giving you an extra control opportunity ahead of the next crop too. This is particularly useful where your drilling has to be delayed for one reason or another.”