Greener for Longer is Key to Yield Building

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Fine-tuning agronomy to extend green leaf retention at the end of the season is one of the most effective ways of boosting wheat yields and breaking the yield plateau affecting UK crops.

That was one of the main messages from a recent ADAS-led Yield Enhancement Network (YEN) event in Peterborough, where growers, researchers and industry sponsors, including leading agronomy firm Hutchinsons, gathered to examine ways to enhance wheat yields.

Maximising light, water and nutrient capture during the summer months is a key way of narrowing the existing gulf between average farm yields at around 8t/ha and the “bio-physical potential” of wheat, which can be up to 20t/ha on some sites, says ADAS Boxworth’s Ian Smillie.

“The bio-physical potential tells you what is theoretically possible, but the focus is what’s attainable.

“Annual cereal crops by their nature don’t have the canopy structure to capture all sunlight available in a season – a typical 11t/ha crop may only capture 47% of total incident radiation for example.

“But, establishing slightly larger canopies early in the season and then keeping them green for longer could increase interception to 60%. By far the largest proportion of that increase comes from 10 days extra greening at the end of the season,” he explains.

Senescence is partly determined by genetics of individual varieties, but is also heavily dependent on water and nitrogen availability, and on protection from disease, so growers should find ways of maximising these throughout the season, but particularly towards the end, he says.

How this is best achieved on farm is a key focus of future YEN investigations, but there are already many things growers can try this season, says Bob Bulmer from Hutchinsons, who stresses that every solution must be tailored to individual situations.

“There are a number of elements that need to be combined to ensure canopies are photosynthetically active for longer.

“Good root systems are important for maximising water and nutrient capture and we are also investigating the physiological benefits of SDHI and strobilurin fungicides on canopies and water use efficiency. The impact of major and minor nutrients on canopy development is another area we are studying.”

dr bob bulmer hutchinsonsDr Bulmer encourages more growers to join the YEN project, which is now in its fourth year. He is keen to point out that YEN’s focus is on identifying ways to maximise the yield potential of individual sites, rather than simply competing to produce the highest-yielding crop.

Prof Roger Sylvester-Bradley of ADAS adds: “Crop productivity has been somewhat lost in the drive to reduce costs over the past 25 years, but YEN is all about looking at how the science of yield can be used to develop unique best practice for every field.

“Focussing on the money and costs means you often miss ways to enhance yield.”

But he acknowledges the cost-effectiveness of different measures needs to be factored into YEN and suggests this could be one project area to develop in future.

If you are interested in taking part in YEN this year please go to or contact Dr Bob Bulmer by emailing: [email protected].

The YEN project is led by ADAS and sponsored by Hutchinsons, Adama, AgSpace, AHDB Cereals & Oilseeds, Bayer, Limagrain, NIAB-TAG, NRM, NFU, Rothamsted Research, de Sangosse, Syngenta and Yara.

Agronomic areas to focus on include:

Encourage more root growth and deeper rooting (ideally down to 2m) to allow access to more water and nutrients, particularly in regions prone to drought stress and early senescence

Improve soil structure and rooting ability by:

  • Reducing compaction (e.g. controlled traffic farming, minimising travel in wet conditions)
  • Minimise cultivations to build natural structure
  • Add organic matter (composts, manures, cover crops) to build soil biology and improve structure
  • Encourage vertical biopores (such as those created by earthworms or deep-rooting crops) to provide conduits for wheat root penetration
  • Consider a “little and often” approach to fertiliser applications, tailored to crop requirements throughout the season, and:
  • Late nitrogen where nitrogen is limiting end of season growth – but beware of scorch risk
  • Improve the water-holding capacity of drought-prone soils – e.g. addition of organic matter or cover crops
  • Maximise the physiological effects of existing fungicide chemistry to improve greening – e.g. SDHIs / strobilurins/ plant growth regulators – use appropriate dose and timing for greening or canopy manipulation, but do not compromise disease control
  • Tailor variety choice to specific field conditions rather than a block-cropping type approach. Later-maturing varieties could help prolong green leaf retention.