Growers dare to boost soybean yields by planting early
Greg Plunk is a betting man. This spring, he’ll plant soybeans as early as soil conditions allow. Neither threat of frost, nor hail, nor conventional wisdom that corn should be planted first will keep him from his appointed rounds.
In 2011, a soybean plot on Plunk’s Mansfield, Ill., farm showed a 5-bu. to 7-bu. yield advantage to early planting across a range of varieties and maturity groups. Planting dates were April 15, May 15 and June 1. A full-season variety planted on April 15 topped the plot at 96 bu. per acre with no irrigation. The entire site, part of a Pioneer Hi-Bred study, averaged 67 bu. in a summer when the word "dry" stuck to the roof of the mouth of every farmer in the area.
Plunk was so impressed with the results that he has added a new 24-row planter to his machinery lineup. This spring, he’ll be able to simultaneously plant corn and soybeans. "I’d like to be planted by April 25. Wet springs have been a problem the last few years, and waiting for the right soil conditions is important too," he says.
"Late frost is a concern with early planting, but the odds of a killing frost are two out of 10 years in this part of central Illinois. A 20% chance of replant is worth the risk to significantly bump yields,"
Proven advantage. Most university researchers around the Corn Belt agree that early planting is part of the formula for producing high soybean yields. Mike Staton, Michigan State University’s Extension soybean educator, notes that farmers who have topped the Michigan Soybean Yield Contest since 2006 have planted two weeks earlier, on average, than the lowest-yielding entries. Data also shows that the high-yielding entries average 10 more pods per plant.
University of Nebraska research shows that for each day planting is delayed beyond May 1, soybeans lose 0.6 bu. per acre under good growing conditions and 0.25 bu. per acre in years with poor growing conditions. "There’s an advantage to planting soybeans in the last half of April or early May compared to mid-May or later planting dates," says James Specht, a University of Nebraska agronomist.
Specht likes to think of the timing risk in terms of expected date of seedling emergence rather than planting date. "Study the probability of late-spring freezes in your local area and consider that, by a conservative estimate, about seven days to 10 days will pass after planting before the seedling emerges," he says.
Beyond freezing temperatures, risks of early planting include soilborne diseases such as pythium. Soybeans generally take longer to emerge when soils are cold. Early planted soybean seedlings also have a higher probabil-ity of experiencing feeding from bean leaf beetles and sudden death syndrome (SDS).
Second looks. Jacob Vossenkemper, a Pioneer agronomy trials manager based in Tuscola, Ill., initiated an early planting management study in 2011 because he thought that more local on-farm
research was needed to validate the feasibility and potential yield gains of early planting.
He planted a short-season and long-season cultivar at early, normal and late timings in 17 on-farm strip trial locations across Illinois and Indiana. The value of seed treatments and the possible need to alter varietal maturity to accommodate early planting were also part of the focus.
"Early planting allows soybeans to initiate reproductive growth sooner and grow reproductively during the longest days of the year, when sunlight is the most intense. This is key because sunlight capture and soybean grain yield are closely related," Vossenkemper says.
"We noticed a significant increase in nodes per plant, which increases the potential for more pods per plant," he continues.
Plant nodes are where the plant produces its flowers, then pods and, ultimately, seeds within those pods.
Moving the planting date earlier typically results in an earlier V1 soybean growth stage—the earliest date that linear node accrual can start. Later planted soybeans rarely catch up in terms of soybean node development.
"We found that long-season varieties definitely had the greatest potential for grain yield increases, especially in central Illinois and southern Indiana," Vossenkemper says.
"Seed treatments also helped mitigate the risk of stand loss from environmental conditions associated with earlier planting. On average, we found the advantage to using seed treatments increased with earlier planting dates."
In the Plunk demonstration plot, the response to seed treatments was noticeably higher yields.
"We had 3.9" of rain the first four days following the earliest planting," Vossenkemper explains. "We ended up with 70,000 more soybean plants in the treated strip and therefore an unusually large yield increase." The initial stand was drilled at 200,000 plants per acre.
Plunk, who also sells Pioneer seed, knows SDS is one of his customers’ main worries. "Varietal SDS tolerance has really improved over the past few years, but it’s definitely something I’m now weighing more heavily as I select varieties," he says.
He also believes improved drainage helps. The early season soybean plot had the advantage of being pattern tiled every 50'.
"We’re still learning, and, because weather and unforeseen conditions can throw curveballs, we want to take a harder look at this next year."
Early Plant Recommendations
If you decide to plant soybeans in the last week of April, consider adapting these tips that Mike Staton, Michigan State University Extension soybean specialist, put together for farmers in his state:
- Don’t plant unless the soil is dry enough to support equipment, and make sure that your planting equip-ment properly operates. Shallow soil compaction and
- sidewall compaction will haunt you for the remainder of the growing season.
- To reduce the potential for frost or freeze injury to emerged seedlings, plant in fields at higher elevations to ensure good air circulation and drainage. Till the field or clear the residue away from the row to allow the soil to warm up faster.
- Consider increasing seeding rates by 10%.
- Treat the seed with fungicides to protect seedlings from soilborne pathogens such as pythium.
- Plant only the highest-quality seed, as overly dry seed or seed with damaged coats will take in soil moisture more rapidly.
- If possible, plant when soil temperatures are expected to be above 50°F for the first six to 24 hours following planting.
- Consider planting slightly shallower if soil moisture is available.
- Reduce the potential for sudden death syndrome (SDS) by using SDS-tolerant varieties and planting into well-drained soils that are free from compaction.
- Scout for bean leaf beetles and other insects and treat when appropriate.