Practical use of the GAI tool in rape in England this year

Lee Bennett, Arable Technical Manager for Openfield, not only uses the BASF GAI tool on www.totaloilseedcare.co.uk for his advice-driven work, but also finds it invaluable for his trials work too.

"It is very important in my day to day work with oilseed rape to be able to accurately measure the Green Area Index or GAI, (the ratio of green tissue area to ground area). It is an effective measurement of assessing canopy size and is used to assess need and timing of both nitrogen and PGRs. I used to measure GAI’s "long-hand" by trying to assess the GAI visually, but over the years I have become very confident in this tools ability to do the job more accurately. I use the BASF GAI tool on a regular basis in trials and on farm," says Lee.

Lee reports that winter oilseed rape crops are looking good at the moment. "Perhaps less advanced than we thought they would be pre-Christmas, but definitely advanced nevertheless, particularly when compared with the last two springs. Oilseed rape crops this year will need active canopy manipulation in order to optimise canopy size and maximise yield potential, whereas last year such an activity was way off the radar. In fact I would be confident enough to say that the vast majority of rape crops would benefit from canopy manipulation with an effective triazole PGR fungicide such as Sunorg Pro this spring."

According to Lee Bennett, some crops, particularly hybrids had a GAI in excess of 2 pre-Christmas but are now back to 1, following the cold weather and some leaf loss. "I can now go and take another snapshot of the crop, close to its first nitrogen application, and be prepared to make a recommendation. With the BASF GAI tool you can upload as many photos as you need over a period of time."

"In Openfield trials where we are growing over 30 different oilseed rape varieties as well as looking at a number of different establishment techniques, it is good to be able to assess the crops biomass along with its root length density and percentage establishment as a measure of success (or otherwise)," says Mr. Bennett.

"In the field the considered use of PGR triazole fungicide on forward crops is a key management activity, resulting in the formation of an optimum sized canopy later in the year, which ultimately translates into yield. Although we have very few late drilled crops this year and a few backward ones, it is important to avoid treating them with a PGR as the yield effects of the PGR fungicides can be negative. Having said that, I am fully confident that this year most rape crops won’t fall into this category."

BASF recommend that when the GAI of the crop is greater than 1 from mid-March, or 2 in April an application of 0.8 l/ha of Sunorg Pro would be beneficial. Applying metconazole at mid-stem extension maximises stem shortening, reduces lodging risk and improves rooting. Used at late green bud onwards Sunorg Pro will maximise canopy effects, reduce lodging risk, improve rooting and contribute to Sclerotinia control.

For further information please contact Lee Bennett, Arable Technical Manager for Openfield on 01476 862702