Current spring-like weather means decisions have to be made regarding oilseed rape agronomy. An overview of crops across the UK by BASF Agronomy Managers reveals there are some very forward crops, however, in some areas pests have been causing problems. Careful nutrition and plant growth regulator (PGR) programmes will be required to manage spring canopies and maximise yield.
Scott Milne in Scotland said, “The size of the oilseed rape canopy is a critical indicator for fertiliser application and plant growth regulation decisions. Measuring a crop’s green area index (GAI) during February and early March, prior to stem extension, is the most effective way to plan fertiliser and PGR strategies over the coming month to six weeks.”
The BASF GAI tool has been developed to provide an accessible and consistent method for estimating the GAI and is available on iTunes:-
https://itunes.apple.com/us/app/osr-gai/id419280577?mt=8
Across the country BASF’s Agronomy Managers have been out assessing oilseed rape crops and measuring GAIs. In the west Robin Rose said, “Crops are further ahead than normal having continued to grow all winter, tapping into unutilised nitrogen from the previous crop and we are now seeing active spring growth. A lot of the crops have a GAI above 2 already, and some are just going into stem extension.”
In the rest of the UK the situation is more variable; Andrew Clune in the south and Matthew Keane in the east report GAIs ranging from 0.8 – 2. Mr Keane added, “ There are a lot of cabbage stem flea beetle larvae in the leaf petioles of oilseed rape plants, as yet they haven’t made their way into the stem but I am fearful of the impact that the larval damage is going to have at harvest.”
Pests of a different variety are currently troubling Scottish growers, Scott Milne said, “Recent attacks by pigeons have caused crops to go back quite dramatically. However, I am not concerned, they will recover.”
Disease wise the Agronomy Managers urge careful monitoring for Light Leaf Spot (LLS). Robin Rose said, “ I have just started to see early signs of LLS coming back into the crop.There is also some phoma in the crop which is not going to be an issue as it is really just on the old dying leaves.”
With promising yield potential in many crops it makes sense to get crop canopy management right to ensure maximum profitability.
Mr Clune said, “ If you measure the GAI of your crop just prior to stem extension and it has a GAI of more than 0.8, then it is economic to treat the crop with a PGR. Bigger is not better in terms of oilseed rape canopies. Small canopies, with an optimum GAI of 3.5 at flowering, capture light more efficiently. Caryx (metconazole and mepiquat chloride)is a true PGR and has a wide application window, it can be used from the start of stem extension through to yellow bud.
Applying Caryx shortens and strengthens the main stem, which helps manage the lodging risk and Caryx changes the architecture of the canopy; you have longer, lower primary branches and a more open canopy that lets in more light producing more seeds/m2and a higher yield. ” Mr Keane added, “Caryx also increases rooting at depth, which really helps in drought years because that is where the moisture is.”
Mr Rose commented, “Because the crops in my area are so big and forward they have a need for a double hit of PGR this year. The rooting is as good as I have ever seen it. Clearly an early application of Caryx will both shorten the crop and encourage further rooting but because we have LLS in the crop, we are going to apply tebuconazole early because it will shorten the stem and sort the LLS out. We are then planning to use the Caryx at the later timing of green/yellow bud to manipulate the canopy.”
