Some soybean producers in Michigan are experimenting with ultra early planting dates (late-March to mid-April) with positive results. To date, research trials have not shown a consistent yield benefit to planting this early when compared to planting during the last week of April or the first week of May. We saw this in replicated on-farm trials conducted in Michigan in 2019 where ultra-early planting increased yield by 6.5 bushels per acre at one location but did not affect yield at two other sites. Given this, the main benefit of this practice is that it enables producers to extend the planting window by taking advantage of good soil and weather conditions that might occur in early to mid-April. Planting soybeans ultra-early carries some risk. These risks and how to mitigate them are:
Imbibitional Chilling Injury (ICI): This condition occurs when the soybean seed imbibes very cold water in the first 12 to 24 hours after planting. Rainfall events occurring within 24 hours of planting favor ICI. This is likely because a cold rain immediately following planting shocks the seedling with a rapid intake of cold water. Cool soil temperatures can prevail without causing significant chilling injury if the seed quality is good, and the soil is not saturated. Visible symptoms of ICI include uneven emergence and dead tissue on the exterior of the cotyledons. Management practices that will reduce the potential for ICI are listed below:
- Plant in the early afternoon to allow soils to warm up.
- Avoid planting when rain is imminent within 24 hours after planting. The heavy rain events that occurred in April and early May 2017 adversely affected soybean germination and emergence in many early-planted fields in 2017.
- Plant high-quality seed having intact seed coats that are free of wrinkles or growth cracks.
- Avoid planting seed having low initial moisture levels.
Seedling Diseases and Poor Plant Stands: Due to the high probability that very early-planted seed will be confronted with cool and wet soils, Michigan State University Extension recommends using fungicide seed treatments when planting early. Select fungicides that are effective against fusarium, pythium, phytophthora and rhizoctonia. Producers should also select varieties that are resistant/tolerant to sudden death syndrome and phytophthora when planting very early. Early planted seed is often in the ground much longer than late planted seed giving more time for diseases to invade the seedling. A good fungicide seed treatment will reduce the risk of poor plant stands.
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