Steps to Better Soybean Yields Next Year

By Jane Fyksen, Crops Editor
Thursday, September 27, 2007 4:47 PM CDT

Combines are already rolling through bean fields in parts of the state. Whether growers view this year’s soybeans with satisfaction or disappointment, there’s always next year.

If you’re looking to improve soybean yields look no further than a new “checklist” developed by Michigan State University and that state’s Soybean Promotion Committee. MSU agronomist Kurt Thelen has teamed up with ag educators Mike Staton and George Silva to sum up management practices “proven to contribute to high-yielding soybeans.”

This checklist goes season-by-season; growers might want to review it to determine the weak links in their soybean systems.

- In the fall, avoid compaction during harvest and fall tillage n Compaction limits rot growth, reduces nodulation, inhibits potassium uptake and promotes diseases such as sudden death syndrome (SDS) and phytopthora. Yield losses due to compaction are variable (15 to 40 percent) and more severe under dry conditions.

- Also this fall, soil sample - Maintain soil pH between 6 and 6.5. University of Wisconsin and Iowa State University researchers have found that soybean cyst nematode populations increased significantly at pH levels over 6.4.

- This is also the time of year to collect and submit soil samples for soybean cyst nematode analysis n SCN causes more economic losses than any other soybean pest. Producers can be robbed of up to 15 bushels per acre before symptoms are even visible. Be proactive and collect and submit soil samples for SCN in the fall before planting soybeans next year. Farms can submit samples free of charge. Contact Craig Grau, UW-Madison plant pathologist, at 608-262-6289 or cg6@plantpath.wisc.edu for more information.

- Apply lime and broadcast potash if need be n Lime typically takes at least six months to react in the soil and potash can safely be applied in the fall to mineral soils having cation exchange capacities of 6 meq/100 grams or higher. (“Meq,” by the way, stands for milliequivalents.)

- Choose next year’s varieties with care n Spend as much time picking soybean varieties as you spend sorting through all the choices of corn. “Variety selection is one of the most important management decisions producers make,” say this MSU team. Consider the following: Yield, SCN resistance, disease resistance or tolerance, standability and maturity.

- Inspect repair and calibrate planting equipment over winter n Uniform seed spacing in the row will improve yield. “Small seed will plant more evenly and experience less mechanical damage than large seed when planted with a drill equipped with a fluted metering system,” these MSU experts say, noting to always calibrate your drill by seeds per foot of row or seeds per acre, and take time to recalibrate whenever seed size changes.

- Control weeds prior to planting with tillage and/or herbicides n “Always plant into weed-free fields,” this trio reminds. “Delayed burndown applications have resulted in yield losses of eight bushels per acre in MSU research trials.”

- Broadcast potash on coarse-textured or organic soils if needed n Fall applications of potash aren’t recommended on coarse-textured soils having CECs (cation exchange capacities) less than 6 meq/100 grams or on organic soils due to the potential for leaching losses.

- Apply phosphate fertilizers if recommended.

- Plant into good soil conditions n Moisture should be adequate and uniform, soil temperature higher than 50 degrees and a level surface promote uniform germination.

- Inoculate seed whenever planting soybeans n MSU and Ohio State University researchers report average yield increases of 1.3 bushels per acre from using inoculants on fields having a history of soybean production.

- Consider a soil-applied residual herbicide application followed by a post-emergence application n Benefits of a two-step program include: Reduced early season weed competition, consistent control of weeds that emerge over a longer time, consistent control of hard-to-control weed foes and prevention of herbicide resistance.

- Plant at the optimum seeding rate n That’s 175,000 seeds in 7.5-inch rows, 150,000 per acre in 15-inch rows and 130,000 for 30-inch rows.

- Plant in narrow rows n Narrow rows have been shown to boost soybean yields.

- Plant at the optimum depth n Plant between 3/4 and 1 1/4 inches deep. “In general, plant at the shallower end of the range when planting early and in no-till, and plant at the deeper end of the range later in the season,” this checklist advises.

- Plant a range of maturity groups n This spreads your risk during the growing season, allows more of the crop to be harvested at the optimum stage and allows for timely wheat planting.

- Use seed treatments where warranted and provide uniform coverage of the seed n Fungicide seed treatments are warranted when planting very early and/or where pythium is known to be a problem. Insecticide seed treatments are recommended when seed corn maggot, wireworm or bean leaf beetle damage is anticipated.

- Monitor fields closely beginning at emergence n Diagnose emergence problems early. Emergence can stretch six to 18 days depending on soil temperature and moisture. If emergence is slow and uneven, dig up the delayed plants and inspect closely for disease or insect damage. Plant stands of 100,000 plants per acre will produce optimum yields if plants are relatively evenly spaced. After emergence, continue checking fields for bean leaf beetles and black cutworms. Monitor weed heights and be timely with post-emerge herbicide applications.

- Apply “post” herbicides on time n That means before weeds are over four inches tall, as early-emerging weeds cause the greatest yield reductions.

- During next summer, identify and correct manganese deficiency symptoms n Yellow, stunted plants growing in dark-colored or high pH soils are likely deficient in manganese. Deficiency symptoms always reoccur in the same areas, as manganese doesn’t build up in the soil. Scout for deficiency symptoms and make foliar applications of manganese when plants are six inches tall. These crop specialists say that manganese sulfate produces the most consistent results. Be sure to keep in mind antagonism when tank-mixing manganese carriers and glyphosate herbicide.

- Monitor and control soybean aphids n Begin scouting late-June and continue through mid-August. Apply insecticides when aphid populations hit 250 per plant and are increasing.

- In the fall of 2008, harvest at the optimum stage and adjust your combine settings to maximize yield and quality n Harvesting beans when moisture content falls to 15 percent for the first time produces the highest test weight and yield. The probability of experiencing harvest losses due to shattering increases when beans undergo several wetting and drying cycles after drying to 13 percent.

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