Tips to increase soybean yields were recently published by two university extension programs. Author Laura Lindsey of The Ohio State University explained her findings in a recent C.O.R.N. newsletter. Similarly, Ignacio Ciampitti, a Crop Production and Cropping Systems Specialist at Kansas State University published his findings on row spacing and the impact on soybean yields. Beyond row spacing, findings on planting date and seeding rate will be analysed.
Leading off with Laura Lindsey of Ohio State, as she explores planting date. Planting date is huge when it comes to soybean yield. She additionally covers some basics about optimal field conditions when planting soybeans. Keep in mind her audience is for Ohio so the optimal date in your area may vary slightly.
Planting date strongly influences soybean yield. In 2013 and 2014, we conducted a planting date trial at the Western Agricultural Research Station near South Charleston, Ohio. In both years, soybean yield decreased by 0.6 bu/ac per day when planting after mid-May. The greatest benefit of planting May 1 to mid-May is canopy closure which increases light interception, improves weed control by shading out weeds, and helps retain soil moisture.
However, planting too early (before field conditions are adequate) comes with a risk. Factors such as damping-off and pressure from bean leaf beetle are concerns to keep in mind, as well as the possibility of a late spring frost.
Do not plant early if the soil is excessively cold or wet. Slower germination and compaction can negate the benefits of the earlier planting date. Timely planting is critical for maximizing yield in soybeans, but using good judgement on field conditions plays a role that is equally important to determining yield potential.
Lindsey works backward from the desired plant population for optimal yield to the needed seeds per acre. She concludes 140K seed / ac is best.
When soybeans are planted in May, a final (harvest) population of 100,000 to 120,000 plants per acre is generally adequate for maximum yield. Final soybean population depends on germination, emergence, disease and insect pressure, competition from other plants, etc. In most situations, 140,000 seeds per acre should result in at least 100,000 plants per acre at harvest.
Lindsey also shares her findings about soybean plant row spacing. Her conclusion is that 7.5 and 15 inch rows yield best.
In Ohio, most soybeans are planted in row widths ≤ 15 inches. Soybeans grown in narrow rows (≤ 15 inches) tend to out-yield soybean produced in wide row width (30 inches) due to increased sunlight interception in narrow rows. Row width should be narrow enough for the soybean canopy to completely cover the interrow space by the time the soybeans begin to flower.
The yield results from her study support the typical Ohio soybean row width conventional wisdom of ≤ 15 inches.
The 30-inch plot yielded 59 bu/acre while the 15 and 7.5-inch plots pictured below yielded 81 and 85 bu/acre, respectively.
Expanding upon the row width research is Ignacio Ciampitti of K-State. His conclusion is that in an environment that supports yields north of 45-50 bushels per acre, narrow spacing is preferred. Specifically his conclusion is the same as Lindsey’s, 7.5 to 15 inch row width is optimal for maximizing soybean yield. Ciampitti shares his research findings.
There are still many questions about row spacing for soybean production. Research from K-State has found that narrow rows (15-inch or 7.5-inch) result in equal or greater yields compared to 30-inch rows when the yield environment is greater than 45-50 bushels per acre (regardless of planting date, seeding rate, or maturity).
Ciampitti notes that yields are slightly better with 30 inch rows if the growing conditions don’t support 45-50 bushels per acre.
Ciampitti explains why narrow rows perform better in favorable conditions.
Narrow rows have several benefits such as early canopy cover, better light capture, improved weed control, and reduced erosion. Poor stands, however, are more common with narrow row spacing versus wider row spacing.
A number of charts illustrating the various locations, row spacing, and resulting yields can be found at the K-State link below. Summarized together, the yield benefit to planting narrow soybean rows is material.
Overall, narrow rows provided a yield response ranging from -0.6 to +5.0 bu/acre. An additional benefit for narrow rows was enhanced early light interception and improved weed control.
Planting date, seeding rate, and row spacing all contribute to your soybean yields. Summarizing three actionable tips to increase soybean yield.
- May 1 through Mid-May is optimal soybean planting.
- Seeding rates should be 140K seeds per acre.
- In growing conditions where soybean yields should be at or greater than 45-50 bu/ac, narrowly space your rows.
Image Courtesy NCSOY.org