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Posted 2 June 2016. PMN Crop News.

Know Your Rows: The Pros and Cons of Narrow Soybean Spacing

Source: United Soybean Board Press Release.

Chesterfield, Missouri (May 11, 2016)--Varying agronomic practices can have an impact on the success of your soybeans, but there’s one key planting decision that shows consistently improved yields without a hefty price tag.


“The Kitchen Sink Project,” a recent soy checkoff-funded study that analyzed the yield results of a variety of soybean inputs, found that planting narrower rows boosted soybean yields by an average of 2.9 bushels per acre. However, many farmers are holding their ground when it comes to planting rows 30 inches, and sometimes more, in width.

Are you having trouble deciding whether to make the switch? Here are a couple of reasons why narrow row spacing might or might not be right for you:

• Pro: The lowest-set pods on narrow-row soybeans are higher than on wide-row soybeans. The higher they are, the more likely they are to make the cut come harvest time. Also, pods that are higher in the canopy produce seeds that weigh more and have higher oil content.

• Pro: Soybeans planted in narrow rows reach canopy closure approximately 15 days before soybeans planted in wider rows. This means weeds aren’t getting the sunlight they need to survive. That 15-day head-start that narrow rows have on canopy closure helps choke out existing weeds and prevent other weeds from seeding.

• Pro: Planting in narrower rows minimizes soil-moisture loss, which can be particularly helpful in a dry year.

• Con: With less sun hitting the soil, your soybeans are more susceptible to diseases that thrive with excessive moisture, like white mold. This might raise alarm if you’re planting in a field with a history of disease.

• Con: While quicker canopy closure in narrow rows will suppress weed growth, wide rows make it easier for herbicides and pesticides to reach the middle- and bottom-third of the plant and the soil.

• Con: Farmers often find that in narrow-row soybeans, petioles in the bottom third of the plant stretch to reach sunlight, making them longer but with smaller leaflets to intercept light. As a result, pods situated lower on the plant sometimes don’t receive the photosynthate they need to survive and will abort.

Bottom line

Fred Below, Ph.D. in Agronomy from the University of Illinois, states that when it comes time to make the decision about whether to plant narrow or wide rows, it’s a trade-off between canopy closure and disease management. Narrow rows offer quicker canopy closure and greater light interception while wide rows offer air movement below the canopy to prevent certain diseases. A firm understanding of what to expect from your geography and field history will help when making this important planting decision.