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Research Highlights

Research Highlights
Determining Suitable Planting Dates, Soil Temps in Western North Dakota

Photo: United Soybean Board

By Barb Baylor Anderson

North Dakota soybean acreage continues to rise, especially in the dry-climate western part of the state. However, no specific management guidelines for no-till dryland soybean production exist for that area. Research funded by the North Dakota Soybean Council is evaluating suitable seeding dates and soil temperatures to help avoid plant stress and create higher, sustainable soybean yields.

“Planting date plays a significant role in soybean production. Early or late planting may decrease grain yield and quality caused by pest or weather stress,” says Gautam Pradhan, North Dakota State University Williston Research Extension Center research agronomist and principal investigator for the research. “The cool, semi-arid climate in the west with annual precipitation of less than 15 inches is at least 5 inches lower than the eastern part of the state. Optimal soybean planting dates are needed for optimum growth to increase production there.”

During the 2018 growing season, soybeans were seeded every week from May 3 to June 15 as part of the trial. Growth and yield were monitored throughout the season, along with soil temperatures and moisture at four-inch depths. Pradhan hypothesizes the optimal soil temperature for planting is likely different than the 50°F recommended for all of North Dakota.

“The trial received heavy rain, wind and hailstorms that damaged the crop and adversely affected yield,” says Pradhan. “Soybeans planted on May 16 produced the highest yield, although soybeans planted on May 10, May 25 and June 9 did not have statistically different grain yields.”

Soybeans seeded on May 16 were three to five inches taller and had better above-ground biomass, test weight and grain protein than other seeding dates. The May 16 maximum grain yield of 17.8 bushels per acre was 3.3 to 6.8 bushels more grain yield than other planting dates.

Overall, Pradhan says growth, grain protein, test weight and yield results showed that mid-May is suitable for seeding soybeans under no-till dryland conditions in western North Dakota.

Another study from 2016-2018 showed that under semiarid no-till conditions, 7.5-inch row spacing with a planting population of 90,000 seeds per acre is more profitable for soybean farmers than combinations using 15-, 22.5- or 30-inch row spacings and planting populations of 120,000 150,000 or 180,000 seeds per acre.

“We repeated the experiment with additional treatments in 2019 and 2020,” he says. “We need several years of study to confirm results and determine that these same principals regarding planting date may also be applied in other states with similar geo-climatic conditions.”

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.