What’s your economic optimum seeding rate?

By John Woodmansee

Years ago, many agronomists seemed to focus solely on what the optimum agronomic seeding rate was for corn and soybeans. In other words, what population do I plant to get the highest yield before yields level off? This discussion may have taken place with little regard to economics. In the current farm economy, we no longer have that luxury. Farmers need to focus on both agronomic principles and economic principles.

An idea proposed by one of my colleagues, David Osborne, Extension educator in Ripley County, was to challenge his local farmers in the past few years to conduct their own field tests. Of course, this is not a new idea. Farmers experiment often, but some may be reluctant and lean toward doing the same thing year after year. The attitude, “we’ve always done it this way,” needs challenged now and then.

So, here’s the challenge that is going statewide this year: Purdue Extension will be initiating a very basic on-farm research program called, “Hide the Strip Challenge.” This is a test involving 3 strips scattered across a field where the grower reduces the seeding rate. Soybean strips need to be wider than the combine head in order to find a full swath when harvesting. Once harvest is complete, the grower’s challenge is to find the reduced population strips on the field’s yield map.

Although this is not a true scientific study, growers may find that seeding rates on their farm can be trimmed somewhat, or at least tested on a larger scale the following year. Multi-year and multi-location studies offer better evidence of real results.

Robert L. “Bob” Nielsen, Purdue corn specialist, has said that the economic seeding rates are typically lower than many are currently planting. Shaun Casteel, Purdue soybean specialist, likewise has conducted studies on minimum soybean populations that still produce good yields. Studies have shown that we can reduce seeding rates below the typical planting rates in corn and soybeans across Indiana (to a point) without hurting yield.

For the purpose of this challenge, Nielsen suggested a reduced rate to try for corn of 29,000 to 30,000/acre (grower’s choice).

Likewise, Casteel suggested trying reduced seeding rates for soybeans:

• Planted with planter units (any row width): 130,000/acre

• Planted with air seeder: 140,000/acre

• Planted with a drill: 150,000/acre

Of course, on-farm studies like this are up to each individual farmer, and what that person may be comfortable with.

If you live in Whitley or Noble County, please contact me and tell me you are trying the challenge this year. I’d like to keep in touch with you, and I’d like to share your findings with our Purdue specialists.

With tight or negative crop production margins, it will pay to find cost savings anywhere you can. After all, it’s not only about how many bushels come out of that combine, but also about how much it cost to get to that point.

For more information on corn, consult Nielsen’s “Chat ‘n Chew Café” website at agry.purdue.edu/ext/corn/cafe. For more information on soybeans, consult Casteel’s “Soybean Station” website, agry.purdue.edu/ext/soybean.

— John Woodmansee is an extension educator in Whitley County.

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