MSU Extension

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

University researchers around the Corn Belt have shown that early planting is critical to producing high soybean yields. The ideal planting time for soybeans is basically the same as it is for corn – the first week of May for the lower half of the Lower Peninsula. However, if soil conditions are favorable and producers manage the crop carefully, soybeans planted during the last week of April can perform as well as beans planted during the first week of May. The risks and the benefits of early planting will be summarized in this article. Specific management practices for early-planted soybeans are also provided.

One of the biggest advantages of early planting is that it provides a longer planting window for attaining maximum yields. Data from the University of Wisconsin and the Ohio State University indicate that beans planted on May 1 will yield about seven bushels per acre higher than beans planted during the last week of May. Beans planted during the last week of April have produced slightly higher yields than those planted on May 1. Dr. Mark Westgate, plant physiologist at Iowa State University and Dr. Palle Pedersen, soybean agronomist at Iowa State University, are proponents of early planting because it extends the vegetative stage leading to more nodes per plant and increases the photosynthesis capacity of the crop canopy. Early planting also promotes more rapid crop growth during flowering and pod set increasing seed number per acre, a key factor to producing high yields. Dr. Pedersen’s data from Iowa shows that early planting is potentially more beneficial in high yield environments than in low yield environments. University agronomists have also found that newer soybean varieties are more tolerant of adverse conditions and produce higher yields than older varieties when planted early.

The primary risk of early-planting is that emerged bean plants will be damaged by freezing temperatures as the growing point is exposed and vulnerable when the cotyledons emerge. This risk is mitigated to some degree by the fact that germination and emergence are delayed under cooler soil temperatures. Soybean tissue is also more resistant to freezing temperatures than corn tissue. Typically, temperatures must reach 28°F for damage to occur.

Another risk to consider when planting early is poor germination and emergence. When soils are cold, beans take longer to emerge. The longer they are in the ground the greater the risk from soil-borne diseases such as pythium and insect feeding. Early-planted soybeans that emerge uniformly and escape freeze injury also have a higher probability of experiencing damage from bean leaf beetles and sudden death syndrome (SDS) than soybeans planted later in the season.

If you decide to plant soybeans in the last week of April, consider the following recommendations.

• Don’t plant unless the soil is dry enough to support equipment and allow planting equipment to operate properly. Shallow soil compaction and sidewall compaction will haunt you the remainder of the growing season.
• Select varieties that have a high level of tolerance to sudden death syndrome. Consider planting soybean cyst nematode resistant varieties as soybean cyst nematode feeding has been shown to increase the severity of sudden death syndrome. Seed treatments have provided inconsistent control of sudden death syndrome.
• Treat the seed with Apron® or Allegience® fungicides or combination products containing either of these fungicides to protect the seedlings from the soil-borne pathogen pythium.
• Till the field or clear the residue away from the row to allow the soil to warm up faster and reduce the likelihood of frost damage to emerged seedlings.
• Plant in fields at higher elevations having good air drainage to reduce the likelihood of frost/freeze injury to emerged plants.
• Plant only the highest quality seed as overly dry seed or seed having damaged seed coats will take in soil moisture rapidly, increasing the likelihood for chilling injury to occur.
• If possible, plant when the soil temperatures are expected to be above 50°F for the first six to 24 hours following planting. If you must plant into cold soils, consider waiting until early afternoon to begin planting to allow the soil to warm.
• Consider planting slightly shallower if soil moisture is available and planting equipment is providing uniform depth control and good seed-to-soil contact. Never plant less than ¾ inch deep.
• Consider increasing seeding rates by 10 percent when planting into cool soils.
• Scout the fields for bean leaf beetles and treat when 50 percent defoliation occurs on beans in the seedling stage or when defoliation exceeds 25 percent during pod set and pod fill.

This article was produced by the Soybean 2010 project. Soybean 2010 was developed to help Michigan growers increase soybean yields and farm profitability. Funding for Soybean 2010 is provided by MSU Extension and the Michigan Soybean Promotion Committee.