So much has been made of the catchphrase “20t by 2020” in wheat-growing circles that it has become folklore. But in reality, can this be achieved within six years – or even at all, asks agronomist Patrick Stephenson.

UK record-holder Tim Lamyman’s wheat crop tipped the scales at 14.36t, which was good, but still 5.64t adrift of the 20t mark. World record-holder Mike Solari hit a large 15.36t in 2008 with his crop of Einstein, but  was still 4.64t short.

The Yield Enhancement Network has stimulated considerable interest in achieving the highest possible wheat yield and Niab Tag and the Foundation for Arable Research (FAR) in New Zealand are working together to try to understand how the highest yields could be achieved. 

See also: Nuffield scholar shares secrets to achieving a 20t/ha wheat crop

Big yields

I recently went on a study tour of New Zealand to explore the potential to increase yields and breaking the 20t/ha barrier. Ever since Mr Solari’s first world-record crop, pilgrims have taken the grand tour to New Zealand in an effort to find what drives big yields.

Adas’ Roger Sylvester-Bradley produced a paper outlining the structure, mechanics and weather that produced the record yield. Niab Tag’s Bill Clark and many farmers, on the other hand, have pointed to the amount of solar radiation in New Zealand compared with the UK, but is this the only answer?

The first distinguishing feature on the mid- and north Canterbury Plains is the absence of wheat. Cows dominate, with centre-pivot irrigators supplying water to help produce grass for 10 months of the year. This provided clue number one – rotation. They are wide and often wheat is planted four or five crops apart.

Clue number two needed a bit of spit and soil texturising to reveal that the arable land is predominantly silt loam to sandy loam, free-draining and deep. Superb for wheat production given sufficient water.

Soil nitrogen

Clue three was the great strength of the sun, that soon became evident without suncream or hat. While discussing nitrogen regimes it became clear that clue four was the available soil nitrogen reserves, which could be as large as 340kg/ha.

I had four big clues, but if it was that simple, why was every year not a potential record?

FAR’s Nick Poole and I are convinced we need a large biomass to create the “source” that could feed the “sink” required for our target. Traditional drilling dates for New Zealand have been April (our October) and to generate more biomass, drilling earlier would be a quick fix.

The 2020 FAR trials I viewed had been drilled in February (our August) sprayed with growth regulator and fungicides in the autumn. They certainly produced a large biomass, but to my eyes they were overgrown brackling at the base and certainly not pretty.

This highlighted that the variety required would need to develop slowly in the autumn while tillering and remaining prostrate over winter.

Ideal variety

Previous varieties that have performed well in New Zealand also had a long grain-fill period – namely Claire, Conqueror and Einstein. The variety in the trial was Wakanui, which has Danish breeding lines. Although it has a long grain-fill period, it develops relatively quickly in the autumn.

Another issue from the early drilling is the susceptibility to barley yellow dwarf virus (BYDV), as the milder, more open, autumn increases the risk of infection. Research by the New Zealand state- sponsored Plant and Food Research organisation has produced a “resistant” BYDV variety, which could prove invaluable with the earlier drilling dates.

What else can research add? One aspect I thought could be useful was the placement of phosphate at drilling. Work undertaken by the HGCA showed the benefit of fresh phosphate on crop yields regardless of the soil indices, although this is not applicable on every soil.

Certainly there appears to be some mileage in trying to increase the root mass over the winter period, but this will require more work. In New Zealand, white clover is grown for seed on many farms and this provides an ideal entry to wheat, producing a deep supply of available N, which can help root development and encourage wheat to develop a larger root ball.

Record holder

To see Mr Solari’s  machinery would bring a tear to many of my growers’ eyes. No 300hp tractors, direct drills and 24m sprayers, but a plough, combination drill, spinning disc fertiliser and a 12m sprayer.

When the weather is right he drills, ploughing only far enough ahead so he can drill tight up to the plough. A wide rotation, including grass, peas, spring barley and rape, planted on relatively small paddocks of about 12ha, with a dedicated agronomist and an enthusiastic farmer, provide the building blocks for big yields.

I fear the wet autumn won’t have helped, but a very respectable yield will still no doubt be achieved.

I can see it being only a matter of time before the wheat record is broken again – and yes, 20t/ha by 2020 could be possible.