PGR is so much more than height reduction

BASF are reminding growers and advisors that creating the best canopy for their advanced crops of oilseed rape is the priority this spring. Clare Tucker, Agronomy Manager for BASF, says that "Rape is a complex crop when it comes to assessing where yield comes from, but we know that too big a crop canopy at flowering means too little light penetration, lower rates of photosynthesis and subsequent lower yields."

"In Spring 2008 and 2009 winter oilseed rape crops were a lot smaller than normal and so canopy manipulation wasn’t high on farmers’ agenda. But this year it is very different scenario and the majority of rape growers will need to focus on creating the optimum canopy size through managed manipulation."

"The majority of growers managed to drill in good time and established their oilseed rape very well this autumn, and, despite the dry start, growth was rapid in October and November. This has resulted in crops that were well advanced going into the winter. The snow had some minor effects, some leaf loss, but not enough to affect the future crop size overall," says Clare.

"Last year’s winter oilseed rape looked so small and disappointing in the spring, yet managed to yield well overall. The UK national yield in 2009 was 3.4 t/ha, 9% above the ten year average. One reason that yields were high last year was that the crop canopy size was naturally small. This year’s crop canopies are already large and will almost definitely need intervention with a plant growth regulating fungicide such as metconazole (Sunorg Pro)."

But Clare says reducing plant height is only a part of what metconazole does to optimise the crop’s potential. "When we think of plant regulation, we think of reducing plant height. Certainly metconazole is effective at doing this, reducing stem height by between 7 to 11 cms, but it does a lot more than this. Its main activity is to reduce apical dominance and so divert growth away from the main stem into branches and roots. By reducing apical dominance, the canopy can achieve better light penetration, improve photosynthesis and improve yield. Branching also helps lock the plants together, so reducing lodging and pod shatter."

"It seems that the impact of lodging is less understood in this crop than, say in wheat, but research has quantified that yield loss due to lodging can be between 13 to 50%. A lodged crop loses seed at harvest and slows down harvesting. And we are also growing some taller rape varieties now, so the need to keep these crops upright is even more important."

"Metconazole has also been proven to show positive rooting effects. Water uptake is vital in the second half of May and June, just the time when rainfall is lower than required, particularly in the East. Sunorg Pro’s use has resulted in 25% more rooting at depth, improved water uptake, leading to extra yields of between 0.22 to 0.34 t/ha in a dry season. ADAS have just completed a study on the frequency of drought stress on winter oilseed rape using regional weather data over the last 23 years. They have calculated that drought stress occurs 1 in every 2-3 years, more often than expected."

Clare Tucker outlines that Sunorg Pro will be an essential part of the management programme this spring. She advises growers and advisors to use the BASF Green Area Index (GAI) tool on www.totaloilseedcare.co.uk to help make accurate recommendations.

"This unique GAI tool helps you get your eye in on which crops are appropriate to treat and when. You upload a photograph of the crop taken from above the crop on an overcast day and instantly will receive a GAI score. This is used to time both fertiliser and metconazole. You should measure GAI twice, once for nutrition in February and again in March for metconazole."

The recommendation is when the GAI of the crop is greater than 1 in March or greater than 2 in April, then apply 0.8 l/ha of Sunorg Pro. Applying metconazole at mid-stem extension maximises stem shortening, controls lodging and improves rooting. Used at late green bud onwards Sunorg Pro will maximise canopy effects, control lodging, improve rooting and contribute to Sclerotinia control.