Biomass - the building block for better yields

Before YEN he had not given much thought to this area. Now it is the starting block for crop managment, with the goal of 25,000 grains/m² come harvest.

“If I can do that and reach a TGW of 50 then it will equate to 12.5t/ha. But to do that I’ve got to achieve ear numbers in the 500/m² mark,” he says.

Two key changes ensued. With varying levels of sand, silt and clay soils it is fair to say Mr Williamson has highly variable soils, so some years ago he set out with variable seed rates. But the key change was to nutrition strategy.

Nitrogen

Generally the total dose of nitrogen has not changed - around 220 kg/n/ha. What has is the balance. Now rather than a first dressing of 40 kg/N/ha, it is more likely to be 70-80 kg/N/ha.

That is followed up by three further splits, ideally three weeks apart. Mr Williamson has moved beyond the traditional three-split approach to four or possibly more. The aim is to ensure nutrients are available to the plant throughout the growing season. It also helps with sulphur applications and reducing leaching early in the season.

“In the past sulphur was part of the first dressing but it doesn’t necessarily complement N application,” he says.

The changes appear to be working. His 2018 entry achieved 11.5t/ha putting him in the top quarter, the highest western region result.

Seed rates

He achieved this without any real increase in seed numbers. His field of Siskin was variably drilled between 105-195 kg/ha to produce a more even plant stand.

“If I am to achieve my goal of a 10t/ha rolling average it’s not so much about improving the best performing parts of the field, but the poorer ones. Adjusting seed rates to soil conditions means our first biomass measurements in early spring showed we already had decent uniformity. Interestingly some of our highest biomass measurements were taken from the areas drilled with the lowest seed rates.

“But it’s also benefits efficiency. I’m working smarter in the field and avoiding unnecessary cost in excessive seed, or fuel being burnt by the tractor.”

The importance of correct seed rate is something he picked up as part of a New Zealand study tour. “Down under they are getting record yields with low seed numbers. Climate and irrigation is a factor but it isn’t the entire story.

Tillers

“By GS31 we are looking for 800 tillers/m². Excessive seed rates will only lead to more tillers and greater biomass and the danger the crop will go over. Too low and you’ll not get the tillers you need for 500 ears/m². That might lead to bigger heads but it doesn’t compensate for the lack of ears and we won’t reach our target of 25,000 grains/m²,” he notes.

To improve things further last season Mr Williamson tried an amino acid biostimulant – with three applications from GS30 to GS39. It is work in progress and he will investigate further this season. However, initial results are promising. “The field certainly appeared to hold on to green leaf area and there was less septoria,” he says.

The other improvement he is looking to make is soil structure and health. As part of a more ‘holistic’ approach he has recently acquired a direct drill with the aim of preserving soil moisture and carbon to build greater resilience. “I’m looking to get roots down right away. If we can improve plant water infiltration it helps get plants going early. If it turns dry we want to hold on to the water, limiting drought effects. I can’t control the weather but I can control our husbandry to try and offset it.”

Threats

But there are downsides which include the risk of the crop falling over and a higher septoria threat. To keep it standing he has beefed up his PGR programme, so that alongside chlormequat he typically adds Moddus (trinexapac-ethyl) or Terpal (ethephon + mepiquat).

Septoria is controlled with a four-spray programme with SDHIs at both T1 and T2. The programme costs around £100/ha but being on top of it early is vital. “We have to kick off with a T0 to keep it under control and then come in with a robust T1 due to the risk in the canopy,” says Mr Williamson

T1 choices will vary but Aviator (bixafen + prothioconazole) is a popular choice. “There are options when it comes to Septoria control. But we have to be mindful of resistance and Aviator comes with a good balance of azole and SDHI. It’s a very convenient option,” he adds.

According to ADAS plant pathologist Julie Smith, crops with early biomass have higher humidity and hold on to leaf wetness for longer, increasing disease severity throughout the season.

“Septoria spreads up the plant via rainsplash. But horizontal transfer is increased in thicker canopies via leaf-to-leaf contact with neighbouring plants,” she comments.

But the threat isn’t just septoria. “Yellow rust spores are particularly sticky so will easily spread in thicker canopies. Maintaining green canopy area during the grain fill period is critical for yield optimisation so a robust disease management strategy is essential to protect post-anthesis source capacity,” she adds.

Another possible problem is the level of N inside the plant – an area that needs further investigation, she says. “Pathogens need carbon and nitrogen to survive and complete their life cycle. Excessive nitrogen within plants is a contributory factor in increased disease levels.”