USING PGRs to manage the canopy of a crop of oilseed rape, might be just as important as using them to reduce height this season, points out an OSR crop expert.

Clare Tucker, the agronomy manager for BASF, has pointed out that creating the best canopy for advanced crops of oilseed rape is the priority this spring. She said: “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,” she pointed out.

“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 cm, 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 achieves better light penetration, improved photosynthesis and better 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,” she says.