Farm Journal Test Plots: Early Start Pays Off for Soybeans

Test Plots see a 3-bu. to 7-bu.-per-acre average increase by focusing on planting date ( Farm Journal Test Plots )

What Ken Ferrie and Missy Bauer Think You Need to Know

  • Early planting dates can increase yields.
  • Soybeans are less sensitive to emergence problems compared with corn.
  • Early planting dates allow for lower average plant populations.
  • Late planting dates need increased population and vertical tillage to improve early growth and canopy closure.

After sudden death syndrome (SDS) reached epidemic proportions in the early 1990s, farmers started planting soybeans later to give the soil a chance to warm up. In the years since, fungicide technology and other management tools have helped in the fight against SDS, but farmers haven’t readjusted their planting dates, sacrificing yield as a result.

In 2017 and 2018, Farm Journal Agronomists Ken Ferrie and Missy Bauer took to the fields to manage planting date and other factors to increase the odds of achieving higher yields.

In two locations in south-central Michigan, soybean treatments included two planting dates (early as in late April or early May and late planting after May 15), two tillage systems (no-till and vertical-till) and two variable-rate (VR) population prescriptions (a difference of 25,000 seeds per acre between the higher and lower average populations). VR planting has proven to be important in Michigan with a six-year average net return of $23.81 per acre. Prescriptions are based on increasing populations in poorer management zones and decreasing populations in productive zones.  

The objectives of the Michigan test plots were three-fold:

  • Determine if planting date and tillage should be taken into consideration when dialing in VR populations.  
  • Evaluate the effect of planting date, tillage and population on the time to canopy closure.
  • Determine if yield components are affected differently based on planting date and tillage as the population changes.

The earlier planting dates resulted in the soybeans reaching 75% emergence 10 to 19 days sooner than the later planting dates. They also reached the V1 growth stage seven to 16 days sooner.

“According to the University of Nebraska–Lincoln, the calendar date of V1 is important since that’s the earliest date linear node accrual can start,” Bauer says. “The sooner plants reach V1, the more opportunity for a higher total number of nodes on a plant.”

The early planting dates increased canopy closure 4.6 to 15 days sooner than the later planting dates. “An earlier calendar date of canopy closure will improve total light capture and potentially lead to increased yields,” she adds.

Canopy closure was also influenced by tillage and population. In the early planted plots, vertical tillage provided better early plant growth and sooner canopy closure. In the late planted plots, higher average VR populations and vertical tillage led to earlier canopy closure.

The number of pods and seeds per plant increased in three out of the four plot locations in Michigan when comparing the early versus late planting dates. The increase in pods came from an increase in nodes per plant and an increase in the number of pods per node depending on location.

“Seed size can also be increased with earlier planting dates, however it’s more related to rainfall timing and maturity,” Bauer explains. “Improving individual plant yield components can lead to increased yields.”

The early planting dates increased yields from 3.1 bu. to 4.8 bu. per acre, with an average increase of 4.1 bu. per acre across all locations in Michigan in 2017 and 2018. That equates to a 6% to 12.7% increase, or an average of 8.6%.

Again, one of the objectives was to determine if the VR prescription should change based on planting date and tillage. The best economical treatment across the sites and years was early planting in a vertical-till environment and a lower population, which when compared with planting later in no-till with a lower population increased yield by an average 6.7 bu. per acre. Planting later in a vertical-till environment and a higher population increased yields an average 3.2 bu. per acre versus no-till and a lower population.

“If the weather forces you to plant late, yields can be increased by implementing vertical tillage and increasing average populations since they lead to earlier canopy closure,” Bauer explains. “Population should be adjusted based on planting date, by increasing it with later dates.”  

Vertical tillage was beneficial in terms of yield in both the early and late planting dates, averaging 2 bu. per acre. However, tillage was not reliably influenced by population.

In central Illinois, the soybean planting window commonly spans three to four weeks in April and May. In 2017, the first week of planting yielded a 6.8-bu.-per-acre advantage versus the other two to three weeks that followed.

The results sparked strong interest in early planted soybeans, and growers responded with intent to push the soybean planting window even earlier in 2018.

As Mother Nature sometimes does, March and April brought snow. With no signs of spring in sight, many farmers began to grow restless.

“We know the risks of planting corn in cold soils, and what poor corn emergence can mean for yield in the end,” Ferrie says. “But soybeans are a little different, losing 20% to 30% of a stand doesn’t mean as much for yield because of the soybean’s ability to branch.”

For this reason, Ferrie recommends, if you can’t sit still, plant soybeans—and that’s exactly what some farmers did in 2018. With the fear of a late spring on their minds, they headed out with less-than-ideal temperature forecasts.

Weather conditions quickly changed, and Illinois went from the second coldest April on record to the warmest May ever.

“When compared with the five-year average for growing degree days [GDDs] accumulated between May 1 and June 21, planting on May 1, 2018 simulated a late March to early April planting date,” Ferrie says. “Soybean growth and development is based on air temperatures, and once the soybeans emerged, the growing degree days began rapidly accumulating.”

The flowering stage is triggered by photoperiod (length of night versus length of day). This is why soybeans typically flower near the summer solstice, he adds.  

In 2018, the GDDs were accumulating fast enough to cause soybeans to flower in the first part of June. The earlier flowering widened the R1 growth stage, which helped the plants start filling the early pods at the bottom while the rest of the plant continued to set flowers and pods.

The earlier flowering also produced more nodes on the plants. The nodes transformed more flowers into pods, again because of the widened reproductive stages, especially at the bottom of the plant.

In 2018, soybean yields were exceptional in Illinois, particularly in earlier planted fields, Ferrie says.

“Looking at more than 500 soybean fields by yield and planting date, there was a 0.72-bu.-per-acre decrease for every day planting was delayed,” he adds.

What does all this mean for planting soybeans in the coming weeks? “Develop a plan to push up planting dates, taking into account tillage and population,” Bauer says.

“Most of the yield comes in the center two-thirds of the plant and some at the top if the weather is good,” Ferrie adds. “Your goal is to add beans at the bottom of the plant.” 

Yield Ananlysis in MichiganYield Advantage to First Week of PlantingFarm Journal Test Plots-Early Soybean Planting


Thank You Plot Partners

AirScout, Can-Am, Case IH, Great Plains, KADL Drone Services, Kinze, New Holland, Trimble, Unverferth, Michigan Soybean Promotion Committee, Finegan Farms, LDK Farms, Miner Farms, Simington Farms, Just a Mere Farms, B&M Crop Consulting and Crop-Tech Consulting

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