Manipulating oilseed rape canopies through the season using fungicides and attention to detail is the key to boosting yields .Gross margins are so tight now that crops cannot be left to compensate poor establishment and will need more management input if the crop is to remain economically viable .
These are the comments of arable farm manager David Fuller of McGregor Farms , a 320ha family business based in Coldstream , who despite atrocius weather conditions last year , managed to produce a satisfactory margin from a crop of Incetintive oilseed rape that spent more time of the winter period under water than above it .
“Investing in a robust fungicide programme where products are selected for disease control as much as crop manipulation will continue to play a key role in our management strategy based on our experiences last year ” , he says.
Oilseed rape has become an increasingly important break crop for the business with 560ha now being grown .
“We don´t have blackgrass up here yet so delayed drilling isn´t such an issue for us , but limited drilling days are , so we have to get one crop off and the land prepared for the next one in a short time window “, says Mr Fuller .
Autumn establishement is key and the plan is to drill low seed rates – around 40 seeds/m2 – aiming for about 25 plants /m2 by the spring .
Up until now , Mr Fuller has applied his first light leaf spot spray based on prothioconazole or tebuconazole , depending in the need for growth regulation , by late October to early November .On very forward crops the preference would be tebuconazole having greater growth regulatory effects than prothioconazole .On crops where establishment would benefit from a boost to vigour , the product of choice is Refinzar (penthiopyrad +picoxystrobin ) at the same timing .The Refinzar not only has activity on ligh leaf spot but also has the added benefit of increasing root mass.
“Refinzar was used last year in a five hectare field trial running alongside the River Tweed ” , explains Mr Fuller .”It was the last field drilled using a variety called Incentive at a seed rate of 440ppm2 in good conditions on August 28th.Spray timing was early November”.
Crop under water for days
What proceeded thereafter was a prolonged period of torrential rain on nothing short of biblical proportions .As Mr Fuller esplains ,the trial plot established well and by early December was at the eight leaf stage .But , on December 5th after heavy rain the Tweed burst its banks leaving the crop six feet under water for three days .
Four further floods with the crop under water for four days on each occasion and he feared for the worst .Boxing Day saw the biggest flood .
“I was surprised that anything survived to be honest ” , says Mr Fuller .”The crop looked awful with plants covered in mud and silt and only the green point of the plant left , but the Refinzar treated plot did have big roots “.
Mr Fuller explains that last year was not a particulary bad season for disease , probably because the crop spent large periods under water and most of the plants had been defoiliated from the flooding .
“However , the oilseed rape was quite last coming into flower too and with the variety Incentive only scroring a six for light leaf spot , it needed the Refinzar to give it some additional disease control ” , he says .”The results speak for themselves and where crops will benefit from a boost to establishment in the autumn we will be using Refinzar simply because the extra rooting in addition to light leaf spot control are reason enough to include it as part of the oilseed rape fungicide strategy ” , explains Mr Fuller .
“On more forward crops , if necessary , we will go with tebuconazole in the spring using half leaf spot and if we want to manipulate growth then we might use a higher rate .”