Oilseedrape seed quality is important in getting the crop off to a good start, sogrowers are reminded not to use seedfrom Glyphosate desiccated crops, as reduced vigour is seen in theseseeds and germination could be impaired, says Hutchinsons technical manager Dick Neale.
Seedrate is an important consideration; seed bed conditions and slug populationsare the two biggest influences on emergence and plant survival so these twoparameters should most influence the choice of seed rate. Established plant populations from15-65 plants/m2 have very limited effect on final yield.
Itsimportant to remember that whether the variety is hybrid or conventional, theback ground to the varietys breeding has no effect on the seed rate.
Thefirst hurdle in successful establishment is seedbed moisture. WOSR seed needsto absorb around 40% of its seed weight in moisture in order for germination tostart adds Mr Neale.
WOSRwill remain viable in dry soil provided that the radical has not broken theseed coat. However, the moment the radical breaks through the seed coat thereis no going back. Moisture levels in the seedbed must then remain at sufficientlevels to take the seedling past fully expanded cotyledons. Any desiccation ofthe seed or seedling during this period will typically see losses of 80-90%.
Postsowing the seed takes around 72 hours to produce the radical when there issufficient moisture, which there often is immediately post drilling. The issueis always retaining sufficient moisture after the initial 72 hours in the latesummer sun and wind.
Toachieve this, growers should sow deeper into moisture, and trial work hasdemonstrated that there is flexibility in the first 5cm of sowing depth beforeany loss of emergence is seen.
Followingon from maintaining seed and seedling moisture, the next aim needs to beminimal soil disturbance as close to the point of sowing as possible, says MrNeale.
Seedto soil contact is of critical importance and research again gives us a set ofparameters to aim for, if consistent and successful establishment is to beachieved. Grass and broad leaved weed emergence and control are also stronglyinfluenced by the establishment method.
Clodsize is a key factor in good establishment and the graph below (Figure 2)demonstrates the almost total failure of the crop to establish in dry clay,once clod size passes 17mm. As a guide, thats the size of the letter keys on acomputer keyboard.
Onthe back of our black grass control work at Brampton, we have developed andpromoted the Cousins Micro-wing establishment system. This moves minimal soilto 75mm depth and drops the seed in behind the leg before rolling in.
Minimalsoil movement techniques like this have raised concerns regarding previous herbicideresidues damaging the WOSR seedlings. However, we have seen no issues duringthe extreme risk year of 2013, where growers had correctly adhered to followingcrop restrictions, he adds.
Cultivationinfluence on pests and disease
MrNeale adds that while chemical control is frequently the main focus ofattention in controlling weeds, pests and disease, the establishment period forWOSR is critical in influencing all of these areas.
Atthe time of writing (mid July), WOSR yields are indifferent, with 3-4.6t/ha thecurrent range.
The3t /ha yielding crops tend to be the earlier sown, close rotation situationsand verticilium wilt again looks to have taken a toll in these cases, withstubbles dead to the ground reported by growers. Later crops, in contrast,have the more normal green stubble once the field is cut.
Ithas been noted in previous years, that earlier sowing in warm soils leaves thecrop at risk from verticilium wilt infection during the autumn.
Rollingof the crop once sown should be considered vital. Rolling improves seed to soilcontact, helps retain moisture and reduces grazing by slugs and Cabbage Stem FleaBeetles. In both cases, there is likely a high mortality rate in these pestssimply by the crushing motion of the Cambridge rolls.
Consolidatedsoil also restricts movement for the pests and induces more surface dwelling,where birds and ground beetles can predate them.