Bringing soybeans in from the cold

A Brandon research scientist is studying the effects of cool temperatures during the Manitoba growing season

soybean plant

A Brandon research scientist is studying how cold temperatures during the growing season can put a chill on soybean production.

Ramona Mohr, who works at the Agriculture and Agri-Food Canada’s Brandon Research Centre, says it starts with a “chilling effect” at planting. Mohr presented preliminary results from her studies at North Star Genetics’ annual soybean grower information day on March 27 in Morris, Man.

Ramona Mohr
Ramona Mohr photo: File

Mohr’s project, initiated last year, will look at methods for reducing the risk of cold temperature damage by evaluating cultivars for cold tolerance in growth chambers, and evaluating appropriate seeding dates and soil temperatures in field tests over two years. Her team is also studying the effects of residue management of the preceding crop on soil temperatures, a study that will continue for an additional three years.

“We anticipate that these research trials will give us a better understanding of potential differences in cold tolerance among cultivars, as well as the effects of residue management, planting date, and soil temperature at a given planting date on soybean development and yield,” said Mohr.

According to Mohr, damage can occur due to cold soil temperatures at seeding, and frost in the spring and fall. Questions also exist about the potential effects of cool temperatures during the growing season.

The “chilling effect” at seeding, according to researchers at Iowa State University, occurs when the seed imbibes water colder than 10 C. This can cause seed vigour damage or seed death.

Growing cultivars adapted to your area, and timely seeding, are important strategies to reduce the risk of cold temperature damage. Manitoba Agriculture, Food and Rural Development recommends several strategies for mitigating cold temperature damage, including planting suitable cultivars, and seeding between May 15 and 25, when soil temperatures have warmed to at least 10 C; 18 to 22 C is ideal.

Mohr’s research will attempt to deliver updated recommendations for growers. The team is midway into growth chamber studies that are evaluating 10 cultivars from Manitoba with crop heat unit maturity levels ranging from 2300 to 2400. Tests evaluate warm germination, at temperatures from 20 C to 30 C, as well as cold germination, at temperatures beginning at 10 C with a pre-chilled substrate.

The test’s preliminary results with an initial seed lot revealed a correlation between the percentage of warm germination and cold germination (respectively), and leaf area and soybean top growth after five weeks. However, Mohr says that it is difficult to separate the effects of seed quality versus the cultivar on these initial results, and further research is needed.

Another study examines the effects of cool conditions at flowering. “The objective was to determine if variability exists among cultivars recommended for Manitoba,” says Mohr.

For this study, 10 cultivars were grown at temperatures of 25 C during the day and 20 C at night. Once flowering, the researchers dropped temperatures to 15 C during the day and 5 C at night, then brought temperatures up to 25 C during the day and 15 C at night. Mohr and her team evaluated the parthenocarpic pod score. “The higher the number, the greater the variety was impacted by cold temperatures,” says Mohr. “The higher the pod set score, the greater the impact by cold temperatures.” The results? Most of the cultivars — so far — have a similar podding index.

While it’s too soon to make recommendations based on the team’s research, Mohr is optimistic that the study will deliver practical results for growers hoping to mitigate the effects of cold temperatures throughout the growing season.

“Through this research, we hope to be able to identify those management practices that may help to reduce the risk of cold temperature damage in soybean in shorter-season areas like Manitoba,” says Mohr.

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