UK wheat yieldshave theoretical potential to more than double over the next 10-20 years ifevery aspect of agronomy is fine-tuned and technological advances are embraced.
That was one of the keymessages at Hutchinsons winter technical conference in Newmarket inmid-January, where speakers urged growers to focus on the many ways to build,not just protect, wheat yields in order to break through the current yieldplateau.
Average UK yieldsincreased rapidly during the 80s and 90s, yet the past decade had seen hardlyany tangible gain, with yields remaining close to 8t/ha. While that comparedwell to other countries globally it was far below the 19-21t/ha geneticpotential of the crop, speakers said.
We dont believe a20t/ha target is that extravagant, said Malcolm Hawkesford of RothamstedResearch, which has launched its 20:20 Wheat initiative that aims to helpgrowers meet this target within the next 20 years.
The UK record yield of14.5t/ha was achieved in 2014 and yield mapping indicates even higherpotential.
Speakers acknowledged oneof the biggest yield-drivers the weather was out of growers control, buturged farmers to do everything they could to better understand how weatherpatterns throughout the season affected crop growth, particularly in terms ofnutrition and disease.
Three key areas werehighlighted for driving future yields, namely; soil and nutrition; diseasecontrol; and seed and variety interactions.
Soil and nutrition
Hutchinsons technicalmanager Dick Neale revealed the company was working with a farm at Hockwold inNorfolk, to provide a dedicated centre for nutritional research. The entirefarm was being soil tested (type, organic matter, pH, and nutrients), mappedand zoned to provide a baseline against which changes to farming practices andagronomy could be measured.
Before you can doanything to correct soil issues, you must measure accurately and know exactlywhat youve got and where it is in the soil profile, said Mr Neale.
He said detailed soiltests could highlight differences that might otherwise have been overlooked,such as interactions between organic matter and cation exchange capacity, thesoils inherent ability to hold onto essential nutrients and provide a bufferagainst acidification.
Soils that can appearsimilar under a standard loam test can be fundamentally very different when yougo into the detail. That will influence how you manage everything from pH tomicronutrients.
Crop rotation and covercropping was another area that played a key role in driving yields, saidChristian Huyghe of French research company INRA. A similar yield plateau inFrance had coincided with a trend towards shorter cereal-based rotations andsharp decline in the amount of peas grown, he said.
Achieving sustainableintensification means both intensification and diversification are necessary infuture. That will be very demanding on knowledge and advice and meansidentifying innovative practices among farmers.
One such innovation thathad potential was direct drilling wheat under permanent alfalfa cover to boostyield potential and protein content, he noted.
Both old and newchemistry had a valuable role to play in driving future wheat yields, JonathanBlake of ADAS also told delegates.
Multisite protectants,such as chlorothalonil, had been around since the 1960s but still gaveworthwhile activity with a low risk of resistance development and formed avaluable component of programmes to reduce selection pressure on azoles andSDHIs, he said.
Fungicide stewardship wasan increasing challenge for the industry, as the recent consultation on thefuture of endocrine disruptors showed, and he urged growers to do all theycould to protect the future of existing chemistry.
That meant not puttingtoo much emphasis on any one type and basing programmes on a combination ofazoles, SDHIs and multisite actives, used protectively rather than incuratively.
Weve seen in the pastwith strobilurins how quickly resistance can develop, he said.
Yield response fromfungicides varies considerably, but with the average response [across HGCA RLdata] close to 2t/ha since 2002, fungicides are clearly an insurance policythat pays out every year.
But it was the physiologicaleffects of fungicides that were key to building yield, as well as protectingit, and therefore breaking the current yield plateau, Hutchinsons technicaldevelopment director David Ellerton said.
Chemistry such asstrobilurins and SDHIs was central to this and could bring many added benefitsbeyond disease control, he said.
Improved root growth,increased chlorophyll production and extra leaf growth were the most notableeffects, which meant plants were better able to extract and utilise water,nutrients and sunlight, reducing stress and ultimately improving yield, hesaid.
Trials had found a0.75t/ha yield benefit from such physiological benefits through reduced droughtstress alone, and Dr Ellerton believed further gains were possible.
Seeds and varieties
Delegates also heard hownew varieties would raise the yield bar in future years, due to advances inplant breeding technology, such as marker assisted trait selection andmolecular mapping.
Hybrid wheat varietiespromised the next level of yield plus improved water and nutrient use,disease resistance and herbicide tolerance, said Syngentas head of cerealsRobert Hiles.
One of the reasons forthe plateau in yields is the relatively narrow range of germplasm being usedacross the current RL varieties. We need to introduce new material andtechnological advances can help do that.
Scots yields plateau too
The UK wheat yield plateau has been repeated inaverage Scottish yields since the 1990s, with barely a 0.02t/ha annualimprovement recorded, says Andrew Gilchrist, managing director of ScottishAgronomy.
Wheat disease and theability to control it is one of the biggest factors, especially given abackground of brooding resistance to key active ingredients, threats to thefuture of azole chemistry and relatively average varietal disease ratings, hesays.
All breeders supplyingvarieties for the HGCA Recommended List are essentially using the same genetictoolkit, with yield being the primary target and most varieties rated 5 or 6for septoria resistance, he says. Since the evolution of the Warrior race, hebelieves yellow rust ratings are also something of a lottery.
There needs to be moreemphasis on disease traits and less on outright yield during the selection ofnew varieties.
Mr Gilchrist says it isvital to use the best chemistry at the key fungicide timings, which means afour, or possibly five-spray approach for winter wheat.
Ever-larger machinery anda succession of wet summers and winters has highlighted the need to protectsoils by minimising compaction, maintaining drainage systems and not forcingseedbeds, he continues. Consider controlled traffic measures, such as keepinggrain trailers on headlands, and more simple steps like regularly check tyrepressures.
Growers may also be ableto increase yields by upping nitrogen rates, he suggests. Many growers are notusing higher historical yields to justify using more than N-Max levels.