UK wheat yields have theoretical potential to more than double over the next 10-20 years if every aspect of agronomy is fine-tuned and technological advances are embraced.
That was one of the key messages at Hutchinsons’ winter technical conference in Newmarket last week (14 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 “yield plateau”.
Average UK yields increased rapidly during the 80’s and 90’s, yet the past decade had seen hardly any tangible gain, with yields remaining close to 8t/ha. While that compared well to other countries globally it was far below the 19-21t/ha genetic potential of the crop, speakers said.
“We don’t believe a 20t/ha target is that extravagant,” said Malcolm Hawkesford of Rothamsted Research, which has launched its 20:20 Wheat initiative that aims to help growers meet this target within the next 20 years.
“The UK record yield of 14.5t/ha was achieved in 2014 and yield mapping indicates even higher potential.”
Speakers acknowledged one of the biggest yield-drivers – the weather - was out of growers’ control, but urged farmers to do everything they could to better understand how weather patterns throughout the season affected crop growth, particularly in terms of nutrition and disease.
Three key areas were highlighted for driving future yields, namely; soil and nutrition; disease control; and seed and variety interactions.
Soil and nutrition
Hutchinsons technical manager Dick Neale revealed the company was working with a farm at Hockwold in Norfolk, to provide a dedicated centre for nutritional research.
The entire farm was being soil tested (type, organic matter, pH, and nutrients), mapped and zoned to provide a baseline against which changes to farming practices and agronomy could be measured.
“Before you can do anything to correct soil issues, you must measure accurately and know exactly what you’ve got and where it is in the soil profile,” said Mr Neale.
He said detailed soil tests could highlight differences that might otherwise have been overlooked, such as interactions between organic matter and cation exchange capacity, the soil’s inherent ability to hold onto essential nutrients and provide a buffer against acidification.
“Soils that can appear similar under a standard loam test can be fundamentally very different when you go into the detail. That will influence how you manage everything from pH to micronutrients.”
Crop rotation and cover cropping was another area that played a key role in driving yields, said Christian Huyghe of French research company INRA. A similar yield plateau in France had coincided with a trend towards shorter cereal-based rotations and sharp decline in the amount of peas grown, he said.
“Achieving sustainable intensification means both intensification and diversification are necessary in future. That will be very demanding on knowledge and advice and means identifying innovative practices among farmers.”
One such innovation that had potential was direct drilling wheat under permanent alfalfa cover to boost yield potential and protein content, he noted.
Fungicides
Both old and new chemistry had a valuable role to play in driving future wheat yields, Jonathan Blake of ADAS also told delegates.
Multisite protectants, such as chlorothalonil, had been around since the 1960’s but still gave worthwhile activity with a low risk of resistance development and formed a valuable component of programmes to reduce selection pressure on azoles and SDHIs, he said.
Fungicide stewardship was an increasing challenge for the industry, as the recent consultation on the future of endocrine disruptors showed, and he urged growers to do all they could to protect the future of existing chemistry.
That meant not putting too much emphasis on any one type and basing programmes on a combination of azoles, SDHIs and multisite actives, used protectively rather than in curatively.
“We’ve seen in the past with strobilurins how quickly resistance can develop,” he said.
“Yield response from fungicides varies considerably, but with the average response [across HGCA RL data] close to 2t/ha since 2002, fungicides are clearly an insurance policy that pays out every year.”
But it was the physiological effects of fungicides that were key to building yield, as well as protecting it, and therefore breaking the current yield plateau, Hutchinsons technical development director David Ellerton said.
Chemistry such as strobilurins and SDHIs was central to this and could bring many added benefits beyond disease control, he said.
Improved root growth, increased chlorophyll production and extra leaf growth were the most notable effects, which meant plants were better able to extract and utilise water, nutrients and sunlight, reducing stress and ultimately improving yield, he said.
Trials had found a 0.75t/ha yield benefit from such physiological benefits through reduced drought stress alone, and Dr Ellerton believed further gains were possible.
Seeds and varieties
Delegates also heard how new varieties would raise the yield bar in future years, due to advances in plant breeding technology, such as marker assisted trait selection and molecular mapping.
Hybrid wheat varieties promised “the next level of yield” plus improved water and nutrient use, disease resistance and herbicide tolerance, said Syngenta’s head of cereals Robert Hiles.
“One of the reasons for the plateau in yields is the relatively narrow range of germplasm being used across the current RL varieties. We need to introduce new material and technological advances can help do that.”
Scots yields plateau too
The UK wheat yield plateau has been repeated in average Scottish yields since the 1990’s, with barely a 0.02t/ha annual improvement recorded, says Andrew Gilchrist, managing director of Scottish Agronomy.
Wheat disease and the ability to control it is one of the biggest factors, especially given a background of “brooding resistance” to key active ingredients, threats to the future of azole chemistry and relatively average varietal disease ratings, he says.
All breeders supplying varieties for the HGCA Recommended List are essentially using the same genetic toolkit, with yield being the primary target and most varieties rated 5 or 6 for septoria resistance, he says. Since the evolution of the Warrior race, he believes yellow rust ratings are also something of a lottery.
“There needs to be more emphasis on disease traits and less on outright yield during the selection of new varieties.”
Mr Gilchrist says it is vital to use the best chemistry at the key fungicide timings, which means a four, or possibly five-spray approach for winter wheat.
Ever-larger machinery and a succession of wet summers and winters has highlighted the need to protect soils by minimising compaction, maintaining drainage systems and not forcing seedbeds, he continues. “Consider controlled traffic measures, such as keeping grain trailers on headlands, and more simple steps like regularly check tyre pressures.”
Growers may also be able to increase yields by upping nitrogen rates, he suggests. “Many growers are not using higher historical yields to justify using more than N-Max levels.
