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Plant growth regulators to enhance wheat yield and quality

In northeast Saskatchewan, as spring wheat growers push for higher yields and better protein levels, lodging can often be a challenge. Researchers and growers were interested in the potential of plant growth regulators (PGR) as an option to help reduce lodging and increase yield and also protein.

PGRs are not new to agriculture and have been used extensively in other cereal growing regions. Some work was done with these products several years ago, but they have only recently been trialed again in Western Canada to see if there have been any improvements in products and how they may fit into production practices. A PGR application can cause various responses in wheat crops, including shorter plants (internodes), thicker stems, thicker stem cell walls, less lodging and potentially higher yields.

Researchers at the Northeast Agriculture Research Foundation (NARF) in Melfort, Sask., began a three-year project in 2013 to demonstrate the plant growth regulator Manipulator (chlormequat chloride) at various application timings and fertility levels in spring wheat.

“We initiated demonstration trials in collaboration with Engage Agro to determine the effects of Manipulator on yield, lodging and height in spring wheat,” explains Jessica Pratchler, field research agronomist with NARF. “The objective of applying the PGR was to help reduce lodging and increase yields. By reducing the height of the crop, more resources are available for seed filling instead of producing stem height. The crop should also be more uniform, improving application timing for inputs and harvest.”

The trials were conducted using the spring wheat variety Shaw VB seeded at 275 plants/m2. Manipulator was applied at the label rate (1.87 L/ha) at three different timings, Zadoks 21 (Z21) or first tiller, Z31 or first node, and Z39 or flag leaf. Based on a soil test rate of 110 kg/ha of N and 25 kg/ha of P2O5, three fertility rates were used at 100, 125, and 150 per cent of the recommendation. For each trial, plant height, lodging and maturity ratings, yield and quality were measured.

“Overall, the demonstration trials with Manipulator proved to be successful in northeast Saskatchewan over the last three years,” says Pratchler. “This product has shown to be highly useful in the northeast as it decreases height and lodging, as well as increases the yield in spring wheat. All three PGR application timings were able to reduce the severity or incidence of lodging, and resulted in shorter plants 94 per cent of the time. Application at Z31 produced the best yields.”

The best results were produced when the product was applied at the Z21 and Z31 stages, however application at the Z31 stage produced the largest decrease in height.

However, if growers also determine a fungicide application is warranted, they can plan to wait and apply the PGR then, which would reduce a field pass. At this stage, a reduction in height is not as significant, but still beneficial.

The trial showed Manipulator in conjunction with high fertility rates can produce a crop with less lodging. In the trials, the fertility rate did not play a large role in the amount of lodging except for the 150 per cent rate with no PGR application, which had the highest lodging rating. In addition, yield, protein, and other grain quality factors were not changed by either PGR application or fertility rate.

Overall, Manipulator application resulted in crop shortening and lodging reduction, regardless of fertility rate or PGR timing, while maintaining spring wheat yields.

In 2015, Manipulator was registered for use on spring, winter and durum wheat in Canada. However, Engage Agro is still waiting for maximum residue limit (MRL) limits to be set by the United States government, which will hopefully be in place by the 2017 growing season.

As with any new products, growers should talk to their grain buyer before applying the product to ensure there aren’t any market restrictions in place.

“Although we have had a lot of interest from growers at our field days, most growers are waiting until the MRLs are in place before trying Manipulator,” adds Pratchler. “Once the MRLs are approved and in place, then NARF has plans to continue with additional research on the use of PGRs in conjunction with different seeding rates, as well as nitrogen levels. We don’t completely understand how PGRs will interact with the whole agronomic package, and therefore more research is needed.”

NARF also has another project underway looking at two different PGRs and their effect on forage crops. They are also collaborating on another project led by Agriculture and Agri-Food Canada researchers in Lethbridge looking at PGR in winter wheat and fall rye.