Advanced OSR crops likely to gain from growth regulation

Article taken from the Farmers Guardian, written by Martin Rickatson

With oilseed rape crops more advanced at this point in the season than for several years, the stage of plants’ growth and the amount of field area they are covering should govern forthcoming agronomy decisions – but assessing those needs the knowledge and technology necessary for accurate measurement.

That was the advice from speakers at a meeting held jointly by Agrovista and BASF.  At which BASF re-emphasised the potential claimed for its OSF metconazole + mepiquat growth regulator Caryx, now entering its first commercial season, and launched an updated green area index (GAI) calculator app for the iPhone.

Commenting on this season’s crops, Agrovista technical manager Mark Hemmant said: “The building blocks for good yields are there – establishment was good, crops have come through the winter very well so far and for those crops drilled using deeper min-till, rooting looks like it has been strong.

“But we still have some way to go with many crops certainly lodging-prone.  Also, the excess biomass present in many crops will create shaded canopies with limited branching potential, show in our Growcrop Gold trials to limit seed set and pod fill.”

Crop potential

Crop potential was concerned with seeds/sq.m and not pods/sq.m, said Mr Hemmant, and growers needed to work back from a target of 7,000 pods/sq.m if they were aiming for optimum yields, with a GAI of 3.5 at mid-flowering – seed number was set in the two-three week period beyond this.

When assessing what was required to get there, in terms of fertiliser application and growth regulation, the 2014 UK crop could be broadly split into three categories, he said.

“There are quick established crops running out of steam as of mid-February and declining rapidly, there are low seed rate crops with good structure and biomass, and there are high seed rate crops which will be vulnerable to lodging and shaded canopy issues.

“These latter crops may well benefit from growth regulation and the delay of a proportion of their planned total nitrogen until seed fill begins, applying as late as possible.  The crop requires 50kg/hectare N for each unit of GAI by the mid-flower stage, so if the crop looks like it has the potential to ultimately achieve that GAI figure, then 175kg/ha N will be the optimum total.”

Growth regulation

While nitrogen management was one arm of crop manipulation, the other was growth regulation, and this could now be more precisely managed than was previously possible, via the secondary PGR effects of application of fungicide such as straight metconazole, said Mr Hemmant.

Caryx, launched last year, is the first dedicated rape PGR on the market and this will be the product’s first full commercial season.

“While straight metconazole stays more localised, Caryx has been shown to have better plant uptake and spread.  ADAS work has shown it is very good at reducing lodging risk as well as managing canopies.  While last year on backward crops at our Growcrop Gold trials site at Morley, in Norfolk, we recorded an additional 0.3 tonnes/ha from a one-litre/ha Caryx-treated trial which had been sown at 20 seeds/sq.m to produce 15 plants/sq.m,” said Mr Hemmant.

“Lodging means more than just harvest difficulties.  It can significantly reduce crop light interception into the crop base, and that can impact on yield.  The product appears to also aid rooting, which again helps anchor the plant and limit lodging while also aiding yield through improved water and nutrient uptake.

“This is attributable to the metconazole element, which improves rooting at depth, while rebalancing the levels of crop biomass from above ground to below.  Even in crops which are standing well, we have seen a 0.4-0.6t/ha yield benefit from its use, which can be attributed to a number of other factors: those rooting improvements, the improved shape of the canopy and better branching, and more light getting into the crop.”

It can only be applied once a season, so lodging prevention applications should be made at stem extension, he added.  For canopy manipulation to improve architecture for light penetration, the advice is to apply at yellow bud stage along with a strobilurin for sclerotinia management.

“A dose of 1.0 litre/ha of Caryx is likely to do a similar job to a full rate of metconazole in terms of growth regulation, but on high-risk, high fertility sites, a full rate of 1.4 litre/ha be required.”

Updated app

Echoing Mark Hemmant’s views on GAI calculation as a tool for oilseed rape crop management, BASF’s Will Reyer suggested that using alongside Caryx could help growers looking to maximise crop branching to make the most of wide rows and light interception.

He said “Canopy manipulation for efficient plant growth and maximum yield is relevant to all rape types, and at both main points in the spraying season – autumn and spring.  While it is currently only approved for spring use, we are hoping to have autumn application on the Caryx label this year.”

OSR crop size

With the size of the OSR crop canopy being a critical indicator for growth, the Caryx GAI app will be a helpful tool in assessing whether GAI figures are on target this season, said Mr Reyer.  The screen which appears with the app shows the size which the photo must be.  Once it is taken, the app takes a few seconds to process the green versus brown areas it sees and produce a GAI figure.

“You should measure GAI in March even if you intend to apply fungicides in April,” said Mr Reyer.

His advice was to then apply Caryx at late green bud at the higher rates (1.0-1.4 litre/ha) on bigger crops (GAI>2) or 0.7-1.0 litre/ha if FAI>0.8.

GAI Tools

Currently available only for the iPhone, the Caryx App can be downloaded from the App store.  Alternatively photos can be uploaded from any digital camera or smartphone to a GAI tool, at www.totaloilseedcare.co.uk

 

21 February 2014

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