Most farmers think of brassica forages as spring-sown crops for extra summer grazing, however, one South Australian dairyfarmer included forage rape in his ryegrass oversowing mix last autumn with impressive results.
Bill Fraser dairy farms at Waitpinga on the southern Fleurieu Peninsula and routinely oversows many of his dryland pastures with extra Italian and perennial ryegrass seed in autumn.
He aims to drill the seed in just before or soon after the opening seasonal rains with the goal being to boost winter growth and thicken up the ryegrass base.
"We sow early in autumn so new seedlings can better compete with the existing pasture and provide a useful boost to winter growth," Mr Fraser said.
After hearing the idea from dairy adviser Neil Lane, Mr Fraser decided to try and further boost winter growth by including forage rape in his seed mix in 2015.
Forage rape seed was added at only two kilograms per hectare in the oversowing seed mix for an additional seed cost of $20 per hectare.
"Knowing brassica seedlings need warm soils to establish well, I reckoned last autumn was a good opportunity to include forage rape," Mr Fraser said.
"We got good early rains at Easter and forecasts were for above average rains throughout autumn, so we acted immediately to include forage rape in the seed mix for 12 paddocks."
Paddocks oversown with rape in the mix were only first grazed at the end of May when pastures had accumulated around 3000 kilograms dry matter (DM) per hectare. Even so, Mr Fraser thought that the rape plants were not well anchored and deliberately grazed other paddocks first.
Nevertheless the forage rape grew well early. Mr Fraser and farm adviser Greg Mitchell estimated it added about 400kg DM/ha at the first grazing, and at least as much again at the second grazing in mid-winter.
"The forage rape seemed to add a second storey to the pasture base without appearing to compromise ryegrass growth underneath," he said.
Forage rape will not tolerate many of the selective broadleaf herbicides commonly used in dairy pastures each autumn.
Mr Fraser said that the farm enjoyed less broadleaf weed problems than normal in 2015, so they were able to delay or omit broadleaf sprays in many paddocks.
"But with hindsight, we should not have bothered including rape in a couple of paddocks known to have heavy weed burdens like mallows," he said.
In summary, Mr Fraser would consider including forage rape in his oversowing mixes in the future, but only in years when he is confident of an early break and continuing rains.D
Background tips Brassica forages like rape have potential for strong autumn growth if sown early with irrigation or early rains.
Bill Fraser's experience was favourable, with the extra growth from added forage rape seed costing him only $25 per tonne DM - but his good result was highly dependent on the solid early opening to the 2015 growing season and reduced incidence of broadleaf weeds.
Most herbicides that control capeweed, mallows, nettles and geranium will destroy brassica seedlings.
Brassica seedlings are strongly susceptible to pests like earth mites, so full insect pest protection is required.
If forage rape is added to autumn pasture mixes, apply nitrogen and sulphur fertiliser to maximise early growth.
Article supplied by DairySA. This project funded by Dairy Australia has been developed as part of the DairySA Hills and Fleurieu Forage Network project. To be kept informed of the project contact email firstname.lastname@example.org or DairySA forage project officer Greg Mitchell. mobile 0417 814 037.