Agronomy Blog

Factors to Consider Before Reducing Soybean Seeding Rates

by Dan Mitchell | Dec 18, 2017

Of the thousands of trials that have gone on in Midwest testing the past 50 years, probably two of the most repeated are probably “How much nitrogen do I need for my corn crop?” and “What is the best seeding rate for my soybeans?” These two questions have been beat to death with at least some agreement….we don’t need as much as we thought 15-20 years ago.

Regarding soybean seeding rates, the trend for many years has been steadily lowering these rates from grandad’s 2 bushels per acre to todays “seeds per acre” jargon of as little as 100,000 seeds per acre or less.

So, what’s the right rate for your soybeans acres? That depends on many factors but for now let’s focus on these points…. Planting Date, “Planting Proficiency”, Seed Quality & Treatment, and Weed Pressure.

Planting Date –
As farms get bigger and more spread out geographically, the need to plant soybeans at the same time, or earlier, than corn is becoming more and more prevalent. Soybeans can tolerate cooler temperatures than previously thought, so why not plant at the same time as corn? Using a high-quality seed treatment, like AgriShieldâ from LG Seeds, is the best insurance for early planting, period!

Planting Proficiency –
“Planting Proficiency” is a term I use to rate how well the seed actually gets put in the ground. Today’s planters/drills are far better than what was used 20 years ago, but still require close attention to maintain good seed-to-soil contact and uniform depth of planting. If you are shooting at lower seeding rates then planter accuracy is critical to get the uniform stands required to make lower seeding rates profitable. There will probably never be a consensus on what the proper planting depth is because several variables come in to play – soil type and condition, current soil moisture conditions and anticipated moisture conditions following planting. Somewhere between 1 to 1½ inches is the most common range with allowances to go shallower in good or wetter conditions and to go deeper in drier situations.

The idea of variable rate soybeans has been around a long time and has merit when you consider seed savings. Using higher rates in lower producing areas and lowering the rate on the better parts of the field has merit. However soybeans don’t seem to show a consistent yield advantage with these systems in every situation.  If you have the ability to change rates “on the go”, then running comparisons on your own farm is the best means of determining if it pays for you. As with variable rate corn, highly variable soils are more likely to show a return than the more uniform ones.

Seed Quality and Treatments –
High quality seed is easy to find these days and 90% germination is normal, but to maximize “stand establishment”, a high-quality seed treatment is a must. Outside of some organic farming we would never dream of planting corn without a good treatment, yet many growers today still put “naked” soybeans out in less than ideal conditions. Seed treatments can be the difference between a so so stand and a good uniform stand. With the combinations of fungicides, insecticides and other biologicals available for 2018, you have a several good options to fit your operations’ needs.

Weed Pressure –
For soybeans to reach their yield potential they need to fill the rows to maximize light interception. Of course, the secondary benefit of this is to slow weed pressure by shading emerging seedlings. If you drop from a seeding rate of 150,000 down to 120,000 or less, you risk the possibility of it taking longer to canopy and lessen weed competition. With some of the vigorous weed species we fight today this makes mean several bushels lost or gained.

Bottom line?
The chart below shows how you can possibly reduce your seeding rates while at the same time staying within the “Best Agronomic Range” for yield and Return on Investment (ROI).

Dan Mitchell-C4845RX citedWith today's’ economy and the need to maximize all inputs, reducing rates from the past recommendations can maintain or add yield while cutting seed cost. Most university researchers agree that a uniform final stand of 100,000 can still yield at a near maximum potential. Unfortunately, all too often the “uniform” part is nearly impossible to maintain. Getting a crop to all emerge evenly and uniformly across hundreds of acres is rarely going to happen. Follow good management practices by planting early, use treated seed, setting your planter for maximum efficiency on rates and depth. These simple suggestions can be the difference between an average crop to a great crop!

Sources and additional information:


Note: The information in this issue is based upon field observations and third party information. Since variations in local conditions may affect the information and suggestions contained in this issue, LG Seeds disclaims legal responsibility therefore. Always read and follow label instructions.
AgriShield® is a registered trademark of AgReliant Genetics, LLC.
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Download a copy of this Technical Bulletin: Tech_361 - Factors to Consider Before Reducing Soybean Seeding Rates