Early planted soybeans: some tips to find your way around

April 14, 2021

Planting soybeans ultra-early—from mid-April to the first days of May—carries some risks. However, this practice, which allows growers to extend the planting window to take advantage of good soil and weather conditions during this period can produce more than positive results when accompanied by proper precautions.

In this article, our team shares some tips for optimizing your early planted soybean yield.

To avoid damage from the cold weather

Soybeans, especially those planted in April, can be damaged from the cold weather when imbibed in very cold water within 12 to 48 hours after planting. This phenomenon is called Imbibitional Chilling Injury. 

To reduce the damage from the cold, it is recommended that you:

  • plant early in the afternoon to allow the soil to warm up;
  • avoid planting when rain is imminent within 24 hours of seeding;
  • plant high-quality seeds, i.e., conditioned (Certified #1), to minimize damage (growth or mechanical cracks) that affect the quality of the seed coat and the quality of the germination.

Damage from the cold is likely to be more severe if the soil temperature is cold (below 4°C) at planting rather than becoming cold 24 hours or more after planting. It is always recommended to plant in soil at or above 10°C.

However, weather forecasts should be monitored for the following ten days, as cold rain immediately after planting will have a negative effect on germination initiation. 

The longer the soybeans remain in the soil in warm temperatures before cold temperatures occur, the lower the risk of damage. Therefore, planting in cold soil should only be done if conditions are perfect.

Note: Soybeans can take 20 to 28 days to emerge when planted in very cold soils.

Table 1: Phytocoenosis and soybean yield at different planting dates (plants/acre x 1,000)
Trial presented at the 2021 Ontario Agricultural Conference and conducted in 2020 by Horst Bohner of OMAFRA. The trial was conducted in southwestern Ontario. Note that there is no frost after soybean emergence, which may explain the constant yields, even for the very early planting on April 22, 2020.

To avoid damage caused by cool and moist soil

Early planted soybeans are likely to encounter cool and moist soils. As a result, the longer soybeans remain in the soil, the more vulnerable they are to diseases such as damping off, caused by Phytophthora sojae, and insects such as the seedcorn maggot. Seeds should be treated with a fungicide to minimize the risk of seedling diseases.

Furthermore, it is recommended to switch to soybean varieties that are more tolerant and resistant to fungi that cause sudden death syndrome, which is widespread in the United States and southern Ontario.

To avoid damage caused by arid soil conditions

If the soil is very dry when planting, it is best to place the soybeans at an adequate depth and not to absolutely plant to moisture, instead plant in dryer soil and allow the first rain to provide the necessary water for a good uniform germination. 

If you try to reach moisture, you risk placing the seeds deeper than two inches and significantly reducing the plant stand.

In addition, it is recommended to aim for a depth of 1 to 1 ¼ inch to promote rapid emergence. Very important: to minimize potential seed energy loss, do not plant deeper than 1 ¾ inch.

Experiment with early planting while minimizing the risks

Last tip: To help maintain soil moisture after planting, it is suggested that you roll the soybean fields with a roller to break apart the soil clods and create an evaporation barrier to conserve moisture around the seed bed.

In addition, pay particular attention to the late frosts that can occur until the end of May, as was the case last year in the Centre-du-Québec region and other small pockets in Ontario.

Happy early planting to those willing to take the risks!