MSU Extension Soybeans

The wet weather conditions that occurred during planting and harvest over the last several growing seasons have created many problems for Michigan soybean producers, such as planting delays, prevented planting, higher charges and discounts at delivery, soil compaction and deep harvest ruts. These conditions reduce yield and income, and managing weather risk will become one of the priorities and characteristics of successful farms in the future. This article summarizes some recent major climatic trends and management practices for reducing weather risk when raising soybeans.

Climatic trends

In general, climate across Michigan and the Great Lakes has become wetter and somewhat warmer in recent decades. As the frequency and amount of available water is a key constraint on crop productivity and Michigan has a relatively shorter growing season than many production areas, at least some of this change has been positive for most of our agricultural production systems. However, there are definitely exceptions as experienced during the 2019 growing season.

The most significant individual climatic trend across the region in recent decades is an increase in precipitation, which has been associated with both more wet days and more rain/snow per event. Annual precipitation totals in Michigan have on average increased almost 4 inches in just the past 50 years (Fig. 1), the result of both more wet days and more precipitation per event. However, there are some important seasonal differences.

Mean summer (June-August) growing season precipitation has increased at a somewhat lower rate, about 0.50-1 inch on average, but the interannual variability of seasonal precipitation totals (total differences from year to year) has decreased, leading to a relative decrease in the frequency and severity of drought conditions with time. Relatively greater increases in precipitation have occurred during the spring, winter and fall seasons, resulting in increases in soil moisture and elevated risks of planting and other fieldwork delays during the spring and harvest in the fall.

In terms of temperatures, mean temperatures in Michigan have warmed about 2 degrees Fahrenheit on average during the past 50 years, but increases have leveled off during the past decade. The majority of the warming has occurred during the winter and spring seasons and at night (daily minimum temperatures have increased more rapidly than daytime maximum temperatures).

One important additional temperature-related trend is a general advance in the timing of the last freezing temperatures of the spring season and a delay in the timing of the first freezing temperatures of the fall, resulting in a relatively longer frost-free growing season with time. As illustrated in Figure 2 for Lansing, Michigan, the last freezes of the spring season have on average tended to occur at least one week earlier, the first freezes of the fall at least one week later, with at least two weeks of additional frost-free season in between.

While the recent observed climatic trends are not a forecast of future conditions, they do offer some potential direction for making more informed management decisions in upcoming growing seasons. They are also consistent with projections of climate in the coming decades. We offer below some thoughts and considerations related to Michigan soybean production.

Variety selection

Select high-yielding and pest resistant varieties. Selecting resistant/tolerant varieties is the best way to manage white mold, sudden death syndrome, phytophthora root and stem rot, and soybean cyst nematodes.

Selecting varieties from a range of maturity groups will help maximize yield potential, extend harvesting window and minimize frost risks. Always select varieties that are adapted to your area as an initial guideline (Fig. 3). For example, in the central tier of counties, a 3.0 maturity group is considered late-maturity, a 2.5 maturity group is mid-maturity and a 2.0 maturity group is an early-maturity variety. Michigan State University Extension recommends the following for matching soybean maturity and planting date.

• Plant late-maturity varieties until May 10 to utilize the longer growing season and maximize yield potential without incurring significant harvest risk.
• Plant mid- and early-maturity varieties between May 10 and June 15 to maintain yield potential and reduce harvest risk.
• Switch to early-maturity varieties after June 15 to maintain yield potential and reduce harvest risk.

Seed quality

High quality seed performs better under stressful conditions than lower quality seed. So, it is important to know the quality of your seed lots and plant the highest quality seed first and the poorest quality seed last. High quality seed is essential when planting soybeans early- to mid-April, so performing a vigor test such as the accelerated aging test or the cold germination test is recommended.

Planting date

Michigan soybean producers have traditionally viewed planting soybeans before April 20 as being too risky. We recommend changing this perception by considering early planting at least as a risk management strategy because it extends our spring planting window. High quality soybean seed can be planted into soil colder than 50 F when soil moisture levels are favorable. Plant some soybeans in April as soon as soil conditions are suitable. When planting in April, consider the following.

• Plant later-maturity varieties to utilize the longer growing season and maximize yield potential.
• Begin planting in the early afternoon to allow the soil to warm up.
• Avoid planting when rain is forecasted within 24 hours of planting to avoid imbibition chilling injury.
• Plant deeper (1.5 to 1.75 inches) except in soils prone to crusting to minimize temperature fluctuations around the germinating seed.
• Use fungicide seed treatments effective on sudden death syndrome and Pythium.
• Select sudden death syndrome and phytophthora resistant varieties.
• Use only high-quality seed having intact seed coats, free of wrinkles and growth cracks.
• Consider planting soybeans before corn, especially when planting into marginal conditions.

Reduce or eliminate tillage

Tillage trials conducted across the U.S. and in Ontario have shown little or no economic return to tilling the soil prior to planting soybeans. Also, no-till soils will become more resilient and forgiving than tilled soils over time.

Seed treatment

As stated above, fungicide seed treatment is recommended when planting early in the growing season, but base seed treatments often provide marginal to no benefits with later planting dates especially in the absence of early-season pathogens. Also, many seed companies will not exchange or take back treated seed if planting is delayed or prevented. Consider this when ordering seed for 2020. Producers that handle bulk seed should work closely with their dealer or downstream seed treater to have their seed treated on an as-needed-basis. Producers that handle bagged seed should make careful decisions regarding how much treated seed to order.

Understand how to manage soils that are prone to developing a crust

Identify fields that are prone to crusting and develop management strategies for reducing the potential for crusting and improving emergence if a crust develops. Some recommended practices are provided below.

• Consider planting in 30-inch rows as the closer within-row spacing enables the seedlings to crack a crust and help each other emerge.
• Plant soybean seed shallow (0.75 to 1 inch) as the hypocotyl will have greater pushing power when the seed is planted a little shallower.
• Do not remove the residue from the row as it protects the soil from raindrop impact.
• Consider planting smaller seed as the cotyledons will be easier to pull out of a crusted soil.
• Use a rotary hoe to break-up an existing crust (avoid the vulnerable crook stage).
• The same planter that was used to plant the field can be used to break up a crust directly over the row.
  • Autosteer is highly recommended to keep the openers on the existing rows.
  • Back-off the down pressure on the openers and increase the down pressure on the closing wheels.
• Wait for a timely rain to soften a crusted soil and improve emergence.
• Transition to long-term no-till and plant cover crops to reduce soil crusting over time.

Reduce soil compaction and eliminate harvest ruts at harvest

Soil compaction and deep harvest ruts create unfavorable conditions for field operations and crop growth. Reduce compaction and eliminate deep harvest ruts to increase your soil’s ability to handle heavy and frequent rainfall. Please consider the following recommendations.

• Avoid performing tillage, planting and harvest operations when the soil is too wet.
• Plant some early-maturity soybean varieties to begin harvesting during the last seven to 10 days of September.
• Plan to complete soybean harvest before Nov. 1 every year.
• Reduce axle loads.
• Avoid random traffic patterns at harvest.
• Grain carts should follow combine tracks whenever possible.
• Match tire/track spacing on combines and grain carts.
• Choose properly sized and configured tires and pay close attention to tire inflation or use tracks.
• Use a high-quality tire gauge or central inflation/deflation technology if possible.

Cover crops

Integrating cover crops into your crop rotation is an important way to build and maintain more resilient and forgiving soils. Producers that are successful with cover crops manage them as intensively as they do their cash crops. They plant and terminate the cover crops on a timely basis. Planting green into small grain cover crops has proven to be beneficial and is recommended when possible.

Plant more wheat in the rotation

Extending corn/soybean rotations by adding wheat offers many benefits to grain producers (including increase in corn and soybean yield), as it is both a cover crop and a cash crop. Adding wheat spreads out the workload for planting and harvest. Every acre of wheat you plant is one less acre of corn or soybeans you will need to plant in a wet spring or harvest in a wet fall.

Having wheat in the rotation also provides excellent options for seeding cover crops. Medium red/June clover can be frost-seeded into the wheat in February or March or a cover crop can be seeded after wheat harvest.

Increase planting and harvesting capacity and efficiency to make the most of good soil conditions

• Equip and operate planting equipment to perform better in marginal soil conditions (one day earlier than normal).
  • Reduce down-pressure on gauge wheels and closing wheels.
  • Add one spike closing wheel per row. This arrangement performs well across a wide range of soil conditions.
• Lease additional planting/seeding equipment and hire the labor to operate and tend it.
• Consider harvesting soybeans at 15 to 16% moisture to reduce risk and improve income.
• Become knowledgeable about drying and storing soybeans.
• Use Draper heads or air-assisted reels to extend the daily harvest window by one to two hours.
• Begin harvesting earlier in the day and run later at night until the pods or straw become too damp and tough.
• Measure harvest losses and increase combine groundspeed when possible without increasing harvest losses

Soybean producers can’t control the weather. However, they can implement pragmatic and practical steps toward managing the production risk associated with adverse weather conditions.