OSR crops established with plant populations as low as 30 plants/sq.m could be best placed to benefit from earlier PGR treatments to manage crop architecture, says Syngenta.
Creating a strong canopy architecture gives the chance to capture more light from your oilseed rape leaf area this season, advocated Syngenta technical manager, James Southgate. Crops at higher plant counts can also be encouraged to hold back the main raceme and develop more side branching, he added. Furthermore, evening up the crop so flowering is concentrated into a synchronised intense period will reduce light reflectance and enable more energy to reach the most efficient leaf area.
With this season’s well growing crops, timing PGR applications at earlier treatment growth stages, typically around GS31, could better develop side shoots and even up the crop, he advised. Treatment on backward crops may be better delayed towards GS51. A shorter crop per se is not the answer, emphasised Mr Southgate. Simple fungicides with some growth-regulating activity on the main raceme can reduce the height, but do not have the same canopy effects as Toprex, to open the structure which enhances light interception and enables plants to build greater yields.
Wiltshire oilseed rape grower Martin Smart topped the Yield Enhancement Network (YEN) oilseed rape results for 2016/17 – demonstrating not just high yield, but also incredible efficiency to get more from the available resources. Grown on free-draining Cotswold brash, where water availability was highlighted as a key threat on the thin, stony ground, Mr Smart attributed his OSR success to deep rooting along with a strong canopy which managed to capture all available light, and turn it into yield.
Achieving the highest ranked yield of 6.4 tonnes/ hectare from his crop of SY Harnas was pleasing, but more pertinent was to achieve gross output yield at 72% of the crop’s calculated potential, he reported. Martin’s target 30 plants/ sq.m gives the chance to create an umbrella shaped canopy which can be managed to capture more sunlight and fill more seeds. With plants growing strongly in spring, he has found PGR treatment can effectively help to manipulate the canopy for light interception. Using Toprex to develop the plant structure is more important than restricting height, with application timing targeted early to trigger greater branching and green leaf area.
In his YEN crop, Mr Smart achieved a total biomass of 16.7t/ha, compared to an average of 13.1t/ha for all YEN OSR entrants. The project calculates a total biomass below 9t/ha is probably low yielding. “Farm trials have demonstrated Toprex can reduce the crop height, but the greatest benefits are in evening up the crop and developing the side branches,” he reported. “We have certainly seen flowering is synchronised into a shorter period, which is beneficial to minimise light reflectance and get more through to the green leaf.”
The high number of seeds generated reinforced the shorter flowering duration was no hindrance to pod set or yield. Furthermore, keeping the crop green for longer, with an application of Azoxystrobin plus SDHI at the sclerotinia flowering timing, enabled the crop to make better use of sunlight. YEN highlights a high TSW crucial for good yields depends primarily on photosynthesis after pod development, determined by canopy health and longevity. Mr Smart’s crop captured an estimated 64% of the potential solar radiation, compared to an average of about 50%.
His result was close to the biophysical annual light interception limit of 70%. “Reviewing the efficiency levels achieved with the YEN crop has been really valuable in thinking about how we manage all the OSR across the farm,” he said. rFor more YEN advice and tips visit the website at www.yen.adas.co.uk
An iOSR grower group visit to the Allerton Trust farm at Loddington, Leicestershire, put the focus on soil health and establishment techniques for oilseed rape. They had the chance to evaluate the first year of trials for ploughing versus minimal tillage or direct drilling, as part of a Syngenta whole rotation stewardship research initiative. Soil structure is possibly more important for oilseed rape than any other combinable crop in the rotation, according to Loddington farm manager Phil Jarvis.
“It’s made all the more crucial by the crop’s generally lazy rooting, and its reliance on the success of getting an essential single tap root down, compared to the more fibrous root system of cereals, for example.”
Mr Jarvis urged growers to dig soil pits to assess earthworm numbers as an indicator of soil health and structure. But he also highlighted the importance of understanding the relationship of soil microbial populations, such as Rhizoctonia strains pertinent to oilseed rape and cereals, which could affect crop establishment throughout the rotation.
The role of companion crops to protect OSR establishment is being closely examined on the Syngenta iOSR Focus Sites this year, including sowing white mustard in with a Clearfield variety – with a view to removing the mustard once the OSR has established. Already there is a clear finding about the mustard
sowing rate and the timing of removal, reported James Southgate. A high seed rate, in good sowing conditions, saw very vigorous early growth which had proven difficult to kill off – and could have already competed with the crop.
“It did appear to have the desired effect in the reduced impact of cabbage stem flea beetle incidence, so maybe next year we will have to look at sowing in alternate rows between the OSR, to see if we can protect the crop, without the competition,” he added.
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