Agronomy: Top 5 Planting Factors for Increasing Soybean Yield

What are your top five factors at planting that can impact your 2015 soybean yields? Everyone can come up with their own list, but I will offer mine.

The top five decisions include variety selection, crop rotation, planting date, row spacing and plant population, and seed treatments. Others might add fertility, soil health or tillage to the list or even other items.

Variety: Variety selection is the number one factor producers should pay attention to when growing beans. Each field has a number of soil and environmental characteristics that make it unique. Selecting varieties best adapted to each field that show top performance will always pay off.

Rotation: Rotating soybeans with corn is one of the best management strategies growers can choose. With growers planting more continuous corn, holding fields for longer periods out of soybeans makes yield potential more favorable than for soybeans. A three-year corn – corn – soybean rotation seems to give the biggest return in terms of soybean yield.

Planting Date: The later beans are planted in May or even into June, the lower the yield potential. Growers should be prepared to begin planting beans as soon as corn is planted or shortly thereafter. Any delays in planting will result in a loss of yield and income. Today’s genetics and seed treatment technology make early planting more viable; risk of a frost is minimal and replant seed is often supplied by the seed company.

Row Spacing and Population: Many growers used to drill beans back in the 1980s and in the 1990s moved to 15-inch row spacing using split planters. Many Midwest agronomists have confirmed over and over again that narrow row beans out-yielded beans planted in 30-inch rows. However, in the past decade we have seen a resurgence in planting beans in 30-inch rows as farmers move to larger planters that can plant both corn and beans. The fact remains that in most years there is a yield advantage planting in narrow rows, be it in 15-inch or 20-inch row spacing.

There has been a lot of field research to determine the optimal soybean plant population. Many growers planted at populations of 160,000 to 180,000 for soybeans planted in 15-inch or 30-inch rows or 200,000 to 240,000 when drilled in 7-inch or 10-inch rows. A lot of field research has shown that there are no yield differences between 100,000, 125,000, 175,000 and 225,000 plants per acre. However, optimal yield is usually found at a harvest population of 100,000 plants per acre, which means planting at a higher rate of 120,000 to 125,000 seeds per acre. Try a lower seeding rate to save on seed costs, but remember to make sure that you target a planting depth of 1.5 inches and that the planter is working properly and evenly dropping seed in the furrow.

Seed Treatments: Today your dealer can treat your seed before you pick it up. It can be treated with a fungicide, insecticide, nematicide and, soon to be available, a treatment to control SDS.  You can top that off by adding an inoculant to make sure your soybeans are maximizing nitrogen fixation. Treating seed is a good risk management tool that enables you to plant earlier and into less than optimal soil conditions and returns back the greatest number of seedlings for each seed planted.

Growers need to pay attention to these five important factors to get their soybean crop off to a good start and have a better chance of reaching their yield goal.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com.