Indiana Prairie Farmer publishes a column written by Tom Bechman with the help of CCAs for CCAs and their clients. With permission from Prairie Farmer we are posting these Corn and Soybean Corner articles on the CCA website. Many thanks to the authors and the support of Indiana Prairie Farmer.
Soybean Corner Articles
Can I cut soybean populations?
Answers are from the Indiana certified crop adviser panel: Betsy Bower, Keystone Cooperative, Lafayette, Ind.; Jeff Nagel, Keystone Cooperative, Lafayette, Ind.; and Marty Park, Gutwein Seed Service, Rensselaer, Ind.
One field got dropped at only 80,000 seeds per acre by mistake last spring, and it made as much or maybe a bushel per acre more than my field across the road at 140,000. It is tempting to just plant 80,000 this spring and cut that seed bill. Would that be a wise move?
Bower: The ideal planting population depends on many factors: date of planting, seed bed condition, weather, soil type and drainage potential, weed issues, soybean lodging in previous years, soybean architecture and potential pests. Just because a population of 80,000 was ideal this year in one field does not mean it will be ideal in every field across the farm.
Try the 80,000 population in more fields next year. Try it in three to five fields that have different issues. Perhaps, plant the lower population in a field with less tillage compared with more aggressive tillage, a weedy field compared with a less weedy field, or a well-drained field compared with a less-than-ideal drained field.
Keep the 80,000 population for the early planting window. Be prepared to replant if needed. Keep in mind your total farm logistics, and try as many fields as you think you can replant timely. As always, consult your seed dealer on planting rates for specific varieties.
It sounds like weed control was not an issue for you in 2024. Soybean competition after closing the rows is one of the most effective weed-control measures in a soybean weed-control program.
Nagel: Soybeans have a tremendous ability to compensate for lower plant stands. This is often through increased branching for nodes to develop and set pods. Ultimately, soybean yields are determined by the number of seeds per acre and seed size. Yield is a function of plants per acre multiplied by pods per plant, seeds per pod and weight per seed.
Across the Midwest, seeding rate trials show that achieving a harvest population of around 100,000 or so on productive soils and 125,000 to 135,000 on lower-productivity soils will reach maximum or near-maximum yields regardless of row spacing. Even at a relatively uniform 80,000 plants per acre, there is general agreement not to replant or add plants. However, to intentionally seed 80,000 seeds per acre carries risk. Emerged rate could be much lower, producing a less-than-acceptable stand.
A target seeding rate of 140,000 is usually a good starting point for row spacing less than 30 inches and 130,000 for 30-inch row spacing. Reduce seeding rates 5% to 15% if you have fields with adequate soil drainage, higher organic matter, lower residue and good planting conditions. Do not overseed fields with a history of white mold. If you are planting early into cool soils with high residue, lower-productivity soil types and/or heavier weed pressure, consider increasing seeding rates by 5% to 15%.
Park: Planting 80,000 seeds per acre can work in some situations, but do not bank on it consistently working in every field every year. This decision gets back to a risk/reward scenario and how big a safety margin you want. Consider your soybean variety, seed treatment, planting date, soil types and planting conditions before making this decision. Thin soybean stands can potentially lead to more weed-control challenges and yield concerns.
