Wallaces Farmer

Soybean planting date and population

4 Min Read

As farming becomes more complex and time becomes more precious, farmers are searching for ways to increase revenue and manage input costs on every acre. This leads us to ask, what soybean management practices can save you time, make the most sense agronomically, and make you money?

What We’ve Learned

At Beck’s six Practical Farm Research (PFR)® sites, it has been observed that planting soybeans during the same optimal window for corn is ideal. In the areas where Beck’s currently does not have a PFR facility, their data relies on university data as they build their cooperator database.

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Planting soybeans earlier can lead to earlier soybean flowering and additional node development (table above). Earlier planting leads to more plant development earlier in the summer. This means achieving more yield potential with reproductive stages of growth beginning at a less stressful period.

Why Early?

Planting soybeans earlier in the season also results in earlier canopy coverage. This earlier canopy coverage leads to cooler soil temperatures throughout the season. On a given day in July, a 7 to 14°F difference in soil temperature could be noted when comparing the earliest and latest planting dates in Ohio. This temperature difference was taken within the canopy cover and further demonstrated how critical early canopy coverage was in maintaining soil temperature.

With nodules performing optimally at a temperature of approximately 72°F (Lynch and Smith, McGill Univ.), cooler soil temperatures lead to an agronomic advantage. More efficient nodules can supply a greater amount of nitrogen (N). This is critical because each bushel of soybeans requires 4 to 5 lb. of N. The graph below demonstrates how closely yield (grey) and N content (green) align based on planting date. Earlier planting leads to greater N content in the tissue and greater yields.

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At earlier planting dates, farmers may be tempted to increase populations. However, data has shown that this is unnecessary. Yield potential is boosted by increasing the number of nodes per plant, pods per node, soybeans per pod, or the size of the soybean. Soybeans will naturally branch and grow toward sunlight if there is room to do so. Allowing soybeans to branch provides more room for pod formation on the plant (image below). By increasing populations, the plant's ability to branch is limited. Later planting and lighter soils will likely respond to higher planting populations.

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While seeding rates as low as 100,000 are not recommend, it’s believed that seeding rates that exceed 150,000 are likely not needed when planting early and/or on more highly productive soils. Beck’s PFR Proven™* data also indicates that lower stands planted early can produce high yields and may not need to be replanted depending on other factors such as uniformity of the stand and weed pressure in the field.

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Soybean yield is a function of the number of nodes per acre. If planted early, even a low population will compensate to produce adequate yields. When evaluating a stand of soybeans for a replant determination, remember that a thins stand early is better than a thick stand planted late. The relationship between planting date and yield is so strong that many farmers should consider planting soybeans first, then planting corn a couple of weeks later, when soil conditions are less challenging.

* In 2017, Beck’s developed the PFR Proven™ endorsement. For a product or practice to become PFR Proven, it needs to have been tested for a minimum of three years and, over those three years, it must provide a positive yield gain each year and average a positive return on investment over the three-year period. These products and practices are a good place to start if you want to try something new on your farm.

Beck’s is the largest family-owned retail seed company in the United States that serves farmers in Illinois, Indiana, Iowa, Kentucky, Michigan, Minnesota, Missouri, Ohio, South Dakota, Tennessee, and Wisconsin. According to a recent seed industry survey, Beck’s ranks as the fourth largest corn and soybean brand in the United States. At their core, all Beck’s employees are Farmers at Heart. It stands for something special. It has soul. It has truth. And it represents a community of farmers, employees, and dealers who strive each day to seek challenges, push boundaries and innovate. Beck’s has, and always will be, proud to serve a community of farmers who love what they do and who are proud to be… Farmers at Heart. For more agronomic new and information, visit Beck’s Agronomy Talk page or blog at BecksHybrids.com.

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