Raise yields with variable approach to growth regulators

Crop protection is the next area that precision farming can have a real impact, believes Simon Griffin, head of science at precision mapping company Soyl. And as a means of getting more farmers interested, Soyl decided to look at plant growth regulators.

Lodging in wheat is caused by number of factors, including roots not being adequately anchored and stem disease. Importantly for farmers, it can prove very costly, reducing yields by up to 75%, as well as hitting quality.

Costs are also higher with the additional drying, which is estimated at up to $10/t. Plant growth regulators, therefore, have a key role in reducing risk by shortening the straw. However, most farmers apply plant growth regulators at a blanket rate.

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That means plants with suboptimal canopies could be further stressed by being further restricted by a growth regulator, while plants with large canopies would benefit from a higher rate, he says. Therefore, matching rates to canopy size could reduce lodging risk. To test this, a trial was carried out in four fields in the UK, which have variable soils ranging from heavy sand clay to sandy loam.

Plant growth regulators

Satellite images were used to assess variation in crop biomass and growth regulators were applied either at a flat rate or variably with thinner areas getting less and thicker areas getting more. Rates of chlomequat and trinexapac-ethyl varied from 80% to 120% of standard rate. “One field saw a huge benefit with a much more uniform crop and less lodging.” Across the trial, the average yield increase was 0.4t/ha with the precision approach.

So why are farmers not doing variable rate growth regulators? Mr Griffin believes there are 3 reasons.

• One limitation is the current kit, which restricted the amount the dose could be varied. “If we could use different equipment, we could have gone lower in some areas and higher in other and may have seen an even greater benefit.”
• Another is tank mixing, as farmers are also applying other products.
• The third is a culture of being risk adverse. Farmers are always going to be cautious and this is something that needs to be overcome.

One solution is to use a direct-injection system, allowing the mix to be varied across the field. A system is being developed at the German Institute for Application Techniques in Plant Protection.

A prototype sprayer has been developed that has shown to be accurate and the researchers believe this approach is now possible in field.