United Kingdom
December 1, 2022
Some winter wheat varieties can be very fussy when it comes to seed rates, while others seem to perform well whether sown thick or thin.
Knowing which is which will help ensure the optimum outcome at harvest and to minimise the chances of over- or underspending on seed.
RAGT Seeds has initiated a series of sowing rate trials to find the answers, part of a programme of work being undertaken by the company to deliver valuable agronomic advice to help growers make the most of its varieties.
This season, the performance of a range of recommended and pipeline wheat varieties drilled in mid October, the middle of the main drilling window, is being assessed, including autumn plant establishment, ear counts and yield.
Three seed rates were used on the chalky loam soil site at RAGT’s headquarters on the Cambridgeshire/Essex border – normal, 20% above normal, and 20% below normal. This equated to 342, 410 and 274 seeds/sq m.
Interesting trends
“We have just finished assessing establishment and we’ve already uncovered some interesting trends,” says RAGT’s technical sales manager Dr Cathy Hooper.
“The obvious point to note is the more seed you put down the more plants you get. But % establishment fell away in nearly all cases, and quite significantly with some varieties, where we increased seed rates by 20%.
“We ended up getting no benefit in terms of hitting our target plant number of 250-260 seeds/sq m, effectively wasting seed.”
This was particularly noticeable with free-tillering, fast-developing varieties such as Skyfall and Extase. The former achieved just 62% establishment when measured in third week of November, or 253 plants/sq m from 410 seeds/sq m; Extase produced similar numbers (see table).
“We’re not sure why establishment was so low – there must be some kind of competition going on, perhaps an allelopathic effect,” says Cathy. “Or does the thicker stand attract more slugs? At this point, we don’t know.”
Lower seed rates
“The key thing is not to over-egg the seed rate – these two varieties in particular did better under lower seed rate regimes.”
At the normal seed rate, Skyfall’s establishment rate climbed to 88%, producing a plant count of 300/sq m.
The optimum for Extase was the lower seed rate, with a 91% establishment, equivalent to 250 plants/sq m – a similar number to the +20% rate without the expense.
Other varieties suffered at the lower seed rate. RGT Rashid’s establishment dropped to 60%, or 165 seeds/sq m; RGT Bairstow was only slightly better.
Both these varieties came into their own at the normal seed rate, achieving over 90% establishment. “In this case, it would have been false economy to cut back on the rate. We know Rashid is more shy to tiller, and it doesn’t pay to cut seed rates on these types,” says Cathy.
Optimum figures
Most other varieties in the trial also produced their optimum figures from the normal seed rate.
Some, including RGT Wilkinson, RAGT’s newly recommended Group 3 variety, achieved good establishment rates at both normal and low rates, 89.5% and 87% respectively in this case. RGT Stokes produced a similar % across all three rates – although free-tillering, it is slower developing, so that was a bit surprising, says Cathy.
“However, to achieve the ideal plant count, you should perhaps avoid going quite so low – perhaps -10% would be a suitable compromise for both RGT Stokes and RGT Wilkinson.”
The plan is to develop the trial in future seasons, including the addition of early and late-drilled datasets.
“At the moment there is a fair amount of statistical noise around this trial,” says Cathy. “But it has provided some interesting insights that will help guide future work and create practical guidelines for our growers.”
Wheat establishment – plant numbers and percentage
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Species
