Spring barley growers are being urged to focus on seed rates, along with nitrogen fertiliser rates and timings, to avoid lodging and big yield loss this season.
Pete Berry, head of crop physiology at crop consultant Adas, looked at root and stem lodging in 2018 and 2020, examining four factors: variety choice, seed rate, nitrogen rate and nitrogen timing.
“It is often a balancing act between yield and lodging risk, but a drilling rate of 300-400seeds/sq m would seem to be optimal, and assessing residual nitrogen and matching that with what is applied is important,” he says.
Lodging results in crops leaning and even falling flat on the ground due to a weak root structure or weak straw strength. This leads to reduced yields and causes harvesting difficulties.
1. Variety choice
All spring barley varieties on the AHDB Recommended List have a score of 7 for resistance to lodging, except for Sassy (6), on a 1-9 scale where a high figure shows good resistance to lodging.
Those scoring 7 include popular varieties such as Laureate, Diablo, Planet and Propino, so there is little difference between varieties.
2. Seed rate
Dr Berry looked at four different drilling rates: 100, 200, 400 and 600 seeds/sq m. He showed that increasing the seed rate gives a weaker stem strength, while higher seed rates reduce slightly the crop’s height.
Increasing seed rates by 100 seeds/sq m was equivalent to reducing varietal lodging resistance to stem/root lodging by 1.5 to 2 points, and vice versa.
So by reducing the seed rate by 100 seeds/sq m, the equivalent lodging rating would increase, for example, from 7 to 8.5-9.
3. Nitrogen rate
The trial demonstrated that raising the nitrogen rate by 50kg/ha was equivalent to reducing the varietal lodging resistance score to stem lodging by 1 point, and cutting the resistance score to root lodging by 0.5 points
4. Nitrogen timing
The work illustrated that delaying the first nitrogen split from applied in the seed-bed to the end of tillering (GS30) was equivalent to increasing the varietal lodging resistant score to stem lodging by at least 2 points, but it also reduced yield.
In addition, Dr Berry found that using a plant growth regulator (PGR) to reduce the crop height by 5cm increased the varietal lodging resistance score by almost 1 point, while larger crop canopies at GS30 were associated with greater lodging risk.
In a further 2019 trial looking at brackling – or when barley heads bend over or snap off altogether – he found that a 10% increase in this condition was associated with a yield reduction of 0.11 to 0.14t/ha, and a crop with 100% brackling could lose more than 1t/ha in yield.
Dr Berry found that PGRs Terpal (mepiquat chloride + 2-chloroethylphosphonic acid) and Medax Max (trinexapac ethyl + prohexadione) applied at GS37, or when the flag leaf is just visible on the main stem, were very effective at reducing brackling in 2019. In the 2020 trials, brackling was seen very late in the season and had little impact on yield.
The 2019 trial showed that when Terpal was applied at 0.75 litre/ha it reduced the crop height by 14cm, while Medax Max applied at 0.4 litre/ha cut the height by 10cm.
All spring barley varieties on the Recommended List score an 8 for brackling resistance, except for Cosmopolitan (7), Sienna (7) Sassy (6) and feed variety Prospect (9).
Pete Berry was speaking at a recent BASF spring briefing.