Maturity Groups, Seeding Rates, Row Spacing and More
  • Environmental conditions can lead to soybean planting outside the recommended window for maximum yield potential. This change requires growers to reconsider their management tactics.
  • Management considerations for late-planted soybeans include changes in:
    • Maturity groups
    • Seeding rates
    • Row spacing
    • Addressing weeds, insects and disease management issues

In the Midwest, soybean planting dates have shifted earlier in the year due to higher yield potential and seed treatment protection against early-season, soilborne diseases associated with cooler, wetter soil. During years when planting is significantly delayed, producers may need to move to an earlier maturity group.

Seeding Rate

When planted in late April or May, the recommended seeding rate in the Midwest is 140,000 seeds per acre. This achieves an average final count of 100,000 plants per acre. If planting is delayed in June, it’s recommended that seeding rates increase.

  • In Ohio, the recommended seeding rate for June is 200,000 to 225,000 seeds per acre.1
  • In Wisconsin, the recommended seeding rate for a mid-June planting date is 200,000 seeds per acre and a target harvest of 180,000 plants.2
  • In eastern Canada, a 10% increase in the standard rate used in a field mid-May is recommended when planting is delayed until mid-June.4

Why is it recommended that the seeding rate be increased when planting late?

A higher seeding rate can increase the chance of setting a higher number of pods to help increase yield potential. Also, a higher seeding rate can increase canopy density, which shades out weeds and helps reduce soil evaporation. This "closes the row" at a quicker rate.3

Row Spacing

If planting in the Midwest is delayed until June, a narrow row spacing (less than or equal to 15 inches) can help maximize yield potential. This happens because narrow row spacing captures more light for photosynthesis and "closes the row" at a faster rate, which better controls weeds and reduces soil evaporation.

Will an increased seeding rate or narrow rows increase the risk of white mold?

Fields with a history of white mold may be at higher risk with increased seeding rates and narrow rows. If the soybean field blooms later, over an extended period, with cool, wet and humid weather conditions, white mold risk may increase. Agronomists advise keeping an eye on weather conditions during bloom. Fungicide application may be necessary.5

Weed Management6

In the rush to plant as soon as conditions are favorable, controlling existing weeds may not be a priority among growers. Late-planting is typically the result of wet conditions. While winter annual weeds may have completed growth and are setting seeds, the priority in many fields should be soon-to-be-emerging summer annual weeds. Always consult with your herbicide provider for available burndown products. Using a residual herbicide can help provide early control. When used in combination with narrow rows, they can provide an effective herbicide management program with late soybean planting.

Late planting usually results in an open canopy for a longer period of time. Will this result in late-season weed escapes?

Fields with a history of waterhemp and fields where a residual product was not applied with either a burndown herbicide or tillage can see this often. If a residual herbicide was not applied before planting or during early post-emergence, continue to monitor the fields and consider a post-emergence herbicide product to control late-emerging weeds

Insect Management

Late soybean planting, especially if it is a single field in the landscape, can attract insect pests and lower populations of other insect pests. Delayed planting often results in less injury by seedcorn maggots and bean leaf beetles. Soybean aphid, stink bug and grasshopper injury may increase.

Soybean aphids developing on vegetative stages of soybean reproduce at a higher rate than when feeding on early reproductive stages. They reach an economic threshold of 250 soybean aphids per plant at a faster rate.3

Seed Treatments

Late planting is usually associated with warmer soil conditions, which enable the seed to germinate quickly and emerge from the soil in less than a week. The need for a seed treatment is not as urgent as it is in early spring.

However, some root diseases like Phytophthora root rot, can still be concerning when planting later in the season. Consider using treated seed in fields with a history of Phytophthora root rot.3

Maturity Group

Many university researchers recommend planting an early maturity group (MG) soybean product when the planting date is delayed until mid-June in the upper Midwest and Eastern Canada. Selecting a soybean product that is no more than 0.5 MG earlier than what is normally planted offers a balance between maximizing yield potential and limited injury from frost (see Figures 1 and 2 for recommended maturity group).

A general rule of thumb is that a 3-day delay from the optimal planting date for your area results in a 1-day maturity delay. Later-planted soybeans will mature at a faster rate than those planted during the normal planting window (see Figures 1 and 2 for recommended maturity group ratings for the United States and Canada).2, 3, 4

Map of recommended soybean maturity groups in the US

Figure 1. Recommended soybean maturity groups by location in the United States. Image courtesy of University of Wisconsin soybean program.


Figure 2. Recommended soybean maturity groups by location for Eastern Canada. Image courtesy of Ontario Ministry of Agriculture, Food, and Rural Affairs.


Burns, E. and Sprague, C. 2019. Weed control recommendations for late and prevented planting. Michigan State University Extension.​