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Soybean Tips

County Agent News
“All Around the Farm”
Dan Folske

April 30, 2018

Soybean Tips

Planting Date:  Soybean is susceptible to frost and prolonged exposure to near-freezing conditions in the spring and fall. Plant soybean after the soil has warmed to 50 F and air temperatures are favorable. Very early planting in cool, wet soil may result in low germination, increased incidence of seedling diseases and poor stands. Planting dates during mid-May are favorable for highest yields with a reduced risk of frost injury. Earlier seeding allows the use of full-season varieties, which typically yield more than shorter-season varieties. Data from date-of-planting studies indicated that late plantings had lower seed yields, poorer seed quality, lower oil content, shorter plant height and pods set closer to the ground compared with optimum planting dates.

SoybeansPlanting Depth:  Plan to plant seed 1 to 1¾ inches deep and place the seed in moist soil. Planting deeper than 2 inches or in a soil that crusts may result in poor emergence and plant stand.

Planting Rate:  Soybean yields have not varied significantly over a wide range of plant populations. A plant population of approximately 150,000 plants per acre is desirable regardless of row spacing. Seeds per pound in available varieties range from 2,200 to 3,400, with an average of 3,000 seeds per pound. High planting rates may cause yields to decrease in low rainfall environments because of drought stress, and in a good rainfall year, high plant populations may lodge more than low populations. Low plant populations reduce lodging but contribute to low pod set and excessive branching. Extremely low seed number per foot of row may result in erratic stands due to lack of seedling energy necessary to break the soil surface. This may be critical in solid-seeded stands where soils are prone to crusting.  Seeding rates should be increased (around 10 percent) to compensate for natural occurring factors that cause some live seeds not to develop into established plants. Slightly higher seeding rates also may be advantageous with late planting dates or in no-till, where soil temperatures are lower. If planting in narrow row spacing (less than 10 inches), soybean seeding rates should be adjusted upward.

Inoculation: Very Important! Some studies, in fields where soybeans have been raised many times, do not always show benefits from inoculation. However, on new fields the difference in inoculation or no inoculation is very high. General recommendation for new fields is to double inoculate using two different types of inoculants. A seed coating inoculant along with a granular drill applied inoculant is a good choice. Inoculants can and do fail so using two completely different inoculants is a good insurance policy. It is important not to let inoculants overheat. When using seed coating inoculants, it is important to get the seed planted as quickly as possible.  If seeding is delayed by rain or breakdowns don’t let it sit out in the hot sun.

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