With the high proportion of hybrid rape in the ground this year, growers of these varieties need to make sure that they manage their crops effectively, not just for yield potential but also to prevent lodging, says Robert Plaice, UK Oilseed Technical Specialist for Monsanto (Dekalb).
"Around 20% of the oilseed rape in the ground this year is estimated to be hybrid, with the variety Excalibur making up three-quarters of that area. Feedback from the field and from our trials indicates that the decision to grow hybrids this year has been well and truly vindicated as these crops have established well and have secured an acceptable plant population in the Spring, not always the case for some conventional varieties," says Robert.
According to Robert, hybrid rape is looking good and is starting to grow away well. "This has implications for Spring growth regulation, which is a key part of managing any high yielding rape crop. As hybrids generally tend to be taller than conventional varieties, they can run the risk of lodging. Although the visual impact of lodging in rape is less startling than in wheat, the effects on yield are just as critical."
"Lodging in oilseed rape compromises the canopy structure, increases disease risk and increases the cost of harvest. If pods are leaning or lying on their sides, they are less exposed to sunlight during the yield-building phase, and yields are reduced. Lodged crop also tend to have more aborted pods, smaller seeds and are more liable to pod shatter. They also create a microclimate that encourages late diseases of rape such as Alternaria and Sclerotinia. Lodged crops are more difficult, more time consuming and more costly to harvest," says Diane Heath, BASF
Oilseed Rape Product Manager.
Robert Plaice suggests that the use of a robust growth-regulating fungicide such as Caramba or Sunorg Pro from stem extension when the crop is actively growing will strengthen and shorten the stems of hybrids and can help to prevent lodging.
"Caramba or Sunorg Pro is the most powerful growth regulator and is particularly effective at stem shortening as well as offering significant rooting benefits. It is important that tall crops such as hybrid varieties on fertile and exposed sites are kept in check. Crops that will beneft from this treatment will be those with a GAI of greater than 1.0 in March or crops with a GAI greater than 2.0 in April. If crops are small and stressed with a GAI of less than 0.5 in March, they would not warrant treatment. We now have the capability of measuring GAI instantly by using the web-based tool on www.totaloilseedcare.co.uk. It really is a very handy tool that makes estimating GAI, and hence the need for growth regulation and nitrogen, much easier to manage. Being able to assess each crop means that you can treat each crop individually and this will have a direct and positive response from inputs," says Robert.
Robert Plaice also points out that some crops, particularly some conventional crops, are patchy with some variation of plants at different stages. "These variable plant stands must be evened out, not just to create an optimum sized canopy to maximise yield potential, but also to make sure that harvesting can take place quickly and efficiently. Here the use of Caramba or Sunorg Pro at a later stage, around late green/yellow bud, will even out branching and lead to a more uniform crop. Stronger branching locks the plants together, reducing canopy movement and pod losses."
