Canopy controls an answer to Agenda 2000 OSRwoes…
Canopy controls an answer to Agenda 2000 OSRwoes…
By Andrew Blake.
BETTER control of oilseed rape crop structure could be the best response to sliding gross margins. That was the reassurance to growers at a Masstock/Cyanamid/ Cargill meeting near Cirencester, Glos last week.
Unless prices rise, which seems unlikely according to Cargills Andrew Bury, winter rape yields will have to rise 0.75t/ha (6cwt/acre) by 2002 to maintain margins as they are now.
Gross margins from an 8.5t/ha (3.4t/acre) crop of winter wheat and a 3.5t/ha (1.4t/acre) crop of winter rape will be roughly the same next harvest, according to Charles Bradfield of Masstock Farm Consultancy.
By 2002 area aid changes will leave the rape margin £100/ha (£40/acre) down and well behind the relatively unchanged figure for wheat, he predicted (see table).
Managing the oilseed rape crop canopy can help redress that balance, said ADASs John Spink. But thick crops may not be best. "Rape has huge potential to compensate and many commercial crops are still far too thick."
"Basically you dont produce any yield before flowering. All you are doing up to June is putting machinery into the factory to convert sunlight to yield. There is no good relationship between the size of the crop at flowering and seed yield."
The optimum ratio of green crop to ground area is 3-3.5 at the end of flowering, most green area coming from pods and stem by then. "You dont want large crops in the spring, because the light absorbed in March, April and May doesnt affect yield."
Sowing rate and date can affect crop structure. Provided establishment is uniform, good yields can be obtained from surprisingly low plant populations.
Along with triazoles, metconazole fungicide, which Cyanamids Eric Gussin hopes will receive approval for spring use, has definite growth regulatory effects which can prove useful, Mr Spink confirmed.
Gross margins (£/ha)
2000 2002
W wheat @ 8.5t/ha 552 549
W wheat @ 7.5t/ha 484 481
W osr @ 3.5t/ha 535 434
CROP DEFOLIATION
Several delegates wondered whether defoliating by mowing or grazing could help manage this seasons over-thick crops. Mr Spink referred to trials mowing Apex to within 2.5cm (1in) of the ground around Christmas in 1996 & 97 and earlier defoliation work. "We have had some fairly reliable yield increases in larger crops and little or no loss even with late sown ones." The key is to ensure the growing points remain untouched, he explained. "If you are using sheep you would probably have to keep them moving."
Crop defoliation
Several delegates wondered whether defoliating by mowing or grazing could help manage this seasons over-thick crops. Mr Spink referred to trials mowing Apex to within 2.5cm (1in) of the ground around Christmas in 1996 & 97 and earlier defoliation work. "We have had some fairly reliable yield increases in larger crops and little or no loss even with late sown ones." The key is to ensure the growing points remain untouched, he explained. "If you are using sheep you would probably have to keep them moving."
Gross margins (£/ha)
2000 2002
W wheat @ 8.5t/ha 552 549
W wheat @ 7.5t/ha 484 481
W osr @ 3.5t/ha 535 434