Arable News

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Time to give second wheats a second look?

Experts suggest that good second wheat performance is one of the key ways growers can improve their farm incomes

Experts suggest that good second wheat performance is one of the key ways growers can improve their farm incomes. Dominic Kilburn writes.

Although the yield gap between first and second wheats is acknowledged to be large, the signs are that as growers apply a more integrated approach to growing them, the gap is starting to close.
Speaking at a roundtable discussion at Agrii’s Throws Farm Technology Centre in Essex, in early August, Agrii’s seed technical manager David Leaper said that there was value in driving second wheat yield performance and that they could represent the best way to improve profit margins on farm.
“We have seen big changes in the past two decades from the influence of weeds, the increase in the oilseed rape area and, more recently, the three-crop rule, and second wheats have found themselves squeezed out of the rotation.
“Trials and agronomist experience are showing us however that the yield gap between first and second wheats can be bridged but the key to it is rooting, which, particularly in the case of second wheats, can be badly affected by take-all,” said Mr Leaper.
According to the National Latitude Second Wheat Grower Studies 2009-2014, only 9 per cent of growers in 2009 were producing second wheat yields within 0.5t/ha of their first wheat yields, but the figure (in 2014) had risen to 25 per cent of growers.
“The signs are encouraging with most of the improvements in second wheat yields being made through growers focusing more on selecting good second wheat varieties and using a take-all seed treatment,” he commented.
He also highlighted the latest Agrii data comparing first and second wheat gross margins and suggested that, when put against a typical 200ha (500-acre) wheat enterprise, the cost of a poor second wheat, or the value of a better one, is nearly 9,000 (45/ha).

Integrated management
Agrii national agronomy manager Colin Lloyd (left) said that a number of factors help second wheat performance and they all need to be factored in to maximise yields.
With a close correlation between drilling date and take-all impact, he advised growers to avoid drilling too early, particularly as take-all inoculum declines with increasing interval from harvest. “Drilling late into October is not a bar to yield as long as crops go in in good conditions,” he commented, with a reminder that later sowing also allows for better control of grass weeds (and volunteers), which themselves can harbour take-all.
“In trials we’ve seen an average 1.1t/ha yield benefit drilling second wheat in late October rather than early October,” he added.
Lower seed rates are also an advantage when it comes to tacking take-all as this results in a greater root mass per plant, he suggested. “Take-all may spread more readily at higher seed rates and so maybe growers should look on the lower end of seed rates combined with a good tillering variety. That said, higher seed rates might still be needed in some late sowing situations.”

N management
Also of benefit to second wheat rooting development was the application of more nitrogen earlier in the season, said Mr Lloyd. “The best second wheat growers are putting more nitrogen on at the end of February and early March – as much as 80-90kg N/ha – plus some sulphur. Applying 40 per cent of the total nitrogen as early in the spring as possible is critical to getting second wheats away.
“Ammonium N may also help combat take-all by lowering soil pH,” he added.
According to Mr Lloyd, any phosphate deficiencies in the soil need to be corrected before the first wheat as P-deficient soils favour take-all, and consider applying foliar phosphite which stimulates root development and helps the crop take up more P.

Breeding resistance
Limagrain UK arable technical manager Ron Granger, said that it was difficult to breed varieties specifically for the second wheat situation although new, evolving, technologies means, that our knowledge of take-all and root diseases is getting better.
He pointed out that, gradually, over seasons, varieties with some resistance to take-all build up and, other important second wheat disease, eyespot can be identified, however RL trials for second wheat performance were limited to the years associated with high root disease pressure.
Limagrain UK trials in Suffolk have demonstrated that second wheat varieties following first wheats that have less susceptibility to take-all, performed better. “We also found that varieties which followed those with Pch1 eyespot resistance performed even better; he explained.
“The lesson here is that growers should look carefully at their choice of first wheat and if it’s a variety that is less susceptible to take-all build up, or one that is Pch1 resistant, then they can be followed with a second wheat,” said Mr Granger.

Seed protection
The greatest second cereal take-all risk comes from high levels of inoculum carryover as a result of early sowing, trash from minimum tillage, poor seedbed consolidation, stubble volunteers and grass weeds, highlighted Monsanto technical manager Barrie Hunt, who added that first cereals were also at risk following a weedy fallow.
“Take-all development is favoured by warm winters followed by wet springs/early summers, however dry summer weather increases losses from compromised rooting.
“It’s likely to be present in most second cereal situations in most seasons,” he claimed.
Mr Hunt said that Monsanto’s specialist take-all seed treatment, Latitude (silthiofam), creates a zone of protection around the seed during the early stages of plant development, controlling primary infection and delaying disease progression.
He said that independent UK second wheat trials (2001-2013) on two sites demonstrated an average yield boost from Latitude of 0.56t/ha over a single purpose seed dressing, delivering typical feed wheat margins of 30/ha or more at current values.

Take-all risk
– Second and third cereals are most at risk through inoculum build-up in previous crops
– First cereals after a weedy fallow are also at risk
– Both winter wheat and barley can be badly affected
– All soil types can foster take-all, with light, peat and chalky downland soils presenting the greatest risk
– Take-all inoculum is likely to be present in most second cereal situations in most seasons


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