Stubble management is an increasingly important tool in the battle against grass-weeds. Farmers Guardian looks at the best approaches to post-harvest cultivations this season.
Alongside the weed burden, the most appropriate stubble management strategy depends on two things – main establishment regime and current cropping pattern, says Bayer glyphosate specialist Tom Scanlon.
Black-grass, bromes and ryegrass problems can be tackled by the same overall approach - leaving seed shed on or very close to the soil surface to be predated, or eliminated with Roundup (glyphosate) ahead of the next crop.
But for meadow, soft and rye bromes, a period on the soil surface to ripen before cultivation is needed, says Mr Scanlon.
“Like black-grass and ryegrass, providing there’s sufficient moisture sterile and great bromes and volunteer oilseed rape will germinate readily in the autumn if left on the surface or under a straw mulch.
“We find the best approach is to avoid cultivating the ground immediately after combining, unless strictly necessary.”
A light roll to maximise seed-to-soil and seed-to-straw contract will ensure the best initial weed flush, he adds.
With sowing of grass-weed infested ground delayed into October there is more than enough time to achieve good stale seedbed control without the need for early cultivations.
Mr Scanlon advises: “Get a good chop of straw and spread it and the chaff evenly and you have a perfect mulch to preserve soil moisture and stimulate volunteer and weed seed germination.”
For growers that are min-tilling, ploughing or ploughing rotationally ahead of autumn or spring drilling without a catch or cover crop, the best approach is to wait until after spraying off the first flush of weed growth before cultivation, and only then if soil conditions are right, says Mr Scanlon.
“If you wait until after your first weed flush in about 3-4 weeks, you’ll generally know you have sufficient moisture to do a decent job of cultivating.”
For the best black-grass control, Mr Scanlon recommends two pre-planting applications of glyphosate at 540grams/hectare at the 2-3 leaf stage with a cultivation in between, followed by a press and roll to get a further stale seedbed control opportunity just ahead of drilling.
If the black-grass has tillered or if ryegrass or bromes are present the rate should be increased to 720g/ha to ensure effective control.
If stubbles are only being sprayed once ahead of autumn drilling after more than six weeks or so, glyphosate rates should be increased to 720 g/ha, he adds.
Minimising soil movement at drilling will ensure the least amount of weed germination in the seedbed.
Where there is a delay of more than a few days between the pre-planting spray and drilling, a permitted glyphosate in the pre-em herbicide mix can be valuable in dealing with new weed emergence, says Mr Scanlon.
Where cereals are late or spring drilled, catch and cover cropping offer an alternative stubble management strategy. However, growers should consider these with caution, he warns.
“Different species have different attributes and work very differently together. It’s important you choose ones that will do the job you want in your rotation. Otherwise, you could end up investing a lot of time, effort and cost for very little gain.”