Optimizing soybean maturity in Minnesota

By Scout Nelson

The spring of 2024 in Minnesota has presented farmers with unexpected challenges, as unusually warm and dry conditions were quickly followed by persistent rains. By early June, despite 80% of soybeans being planted, some fields need replanting due to adverse weather.

The University of Minnesota provides guidance for farmers facing delayed planting or replanting situations. Traditionally, if soybean planting is delayed until June 10, it's advised to reduce the relative maturities (RMs) of soybean varieties by 0.5 points to balance yield potential against frost risk.

This year's variability necessitates careful decision-making. Farmers must consider several factors:

• Whether the situation involves delayed planting or replanting.
• Availability of seed and whether it matches the maturity of earlier-planted soybeans.
• The farmer's risk tolerance regarding potential frost damage.

Local research suggests minor RM adjustments (about ±0.5 units) have minimal impact on yield but can influence the final maturity and harvest timing.

A detailed soybean modeling project supported by the Minnesota Soybean Research & Promotion Council has provided a phenology predictor tool. This tool, using data from 2000 to 2022, helps predict maturity dates based on variety, planting date, and location.

For example, in the Southwest region of Minnesota, a 2.0 RM soybean planted on May 10 is predicted to reach R7 (physiological maturity) around September 27.

If planting is delayed to June 10, the same variety would mature about 12 days later, on October 10. Adjusting to a 1.5 RM could bring the maturity date closer, minimizing the delay.

Farmers must weigh their options based on their specific circumstances:

• Farmer #1: Decides to stick with their current seeds despite potential delays in harvesting, as they can manage the logistics and accept minor frost risks.
• Farmer #2: Chooses a slightly earlier RM for replanting to ensure quicker maturity of drowned-out spots, aiming to synchronize harvest times.
• Farmer #3: Opts for a full RM reduction for a quicker and more synchronized maturity with the rest of their crop, prioritizing seamless harvest operations.

Strategic RM adjustments can help farmers manage harvest schedules without significantly affecting yield potential, especially in erratic weather like 2024. This flexibility allows farmers to adapt and maintain productivity despite challenges.

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