May 3, 2016 - 12:19am -- foxx.2

Basic Soybean Agronomics

The 2016 row crop planting season is underway.  Recently Laura Lindsey, OSU Extension soybean specialist wrote an article summarizing some basic soybean agronomic factors including planting date, planting rate and row widths.  The following is an excerpt from that article:

Planting date.  Planting too early or too late can reduce soybean yield potential.  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.  (Note: Soil temperatures were >50°F at each planting date.)  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. 

Planting too early 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.  (Our early May planting date in northeastern Ohio in 2013 was damaged by bean leaf beetle and two frosts that occurred mid-May.)  Before heading to the field, consider the conditions you will be planting into.  Soybean germination begins when soil temperatures reach 50°F and moisture is present at the planting depth of 1-1.5 inches.  With these conditions, emergence can typically be expected 2-3 weeks after planting.  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.

Seeding rate.  What is the optimum soybean seeding rate?  On-farm research conducted by the Ag Crops Team from 2004-2014 with soybeans planted in either 15 or 7.5 inch rows indicates that 116,000 plants/acre at harvest resulted in a relative yield of 90% (i.e., If 100% yield is 50 bu/ac, 90% yield is 45 bu/ac) when soybeans were planted in May.  Soybeans can yield well over a wide range of seeding rates. 

Row spacing.  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 inter row space by the time the soybeans begin to flower.  In our 2015 row width study, soybeans grown in 7.5 and 15-inch rows yielded similarly while soybeans grown in 30-inch rows yielded on average 15-20% lower. 

Fruit Growers: Prepare for the 17-Year Cicada Emergence

The eastern half of Ohio, including Wayne and surrounding counties, is due to experience the emergence of the 17-year cicadas sometime around mid-May although the exact timing depends upon soil temperature and weather conditions.  This cicada requires 17 years for the development from the nymph stage to the adult stage of this insect.  The vast majority of that time is spent underground, living off sap from plant and tree roots.   After completing development below ground the mature nymphs will construct a tunnel to the soil surface and emerge.  Upon emergence the nymphs climb onto any nearby vegetation or vertical structure, and molt to the winged adult stage by shedding their exoskeleton.  These adult cicadas only live for a 2-4 week time period.   Although cicadas may emerge in a mass over a tight time period of several nights, it is also possible that weather conditions could cause emergence over a several week period.  Cicadas are generally associated with a lot of noise as the males “sing” to attract females. 

For fruit and woody ornamental growers the 17-year cicada emergence presents a real economic threat.  Following mating the adult female cicada makes a series of slits in woody stems, and then inserts an egg into each slit.  Anywhere from one to several dozen eggs can be laid in one branch.  Each female can lay up to 400 eggs, usually deposited in 40 to 50 different sites.  Cicadas prefer to lay eggs in woody stems that at are ¼ to ½ inch in diameter, which is a size commonly found in young apple and peach trees and in blueberry, grape, and raspberry plants. Terminal leaf clusters often wilt and die on stems that are injured, leading to a tree with ‘flagging’ symptoms.  Eggs typically hatch in 6-10 weeks.  The newly hatched nymphs fall to the ground and then burrow underneath the soil surface to a 6-18 inch depth where they will remain for another 17 years.

Celeste Welty, OSU Extension Fruit Entomology Specialist, recommends that fruit growers in affected areas avoid planting new nursery stock this spring; wait until autumn or next spring.  Mechanical control in existing plantings can be done by using ¼ to ½-inch netting to exclude the cicadas and injured stems can be pruned and destroyed before eggs hatch.  Orchards should be scouted frequently to look for the start of egg-laying injury; beginning one week after cicada “singing” is heard.  Chemical control can be used by applying insecticide, starting when egg laying begins and, if needed, repeated 7 to 10 days later.

Contact the Wayne County Extension office at 330-264-8722 for more information about cicada control options.

Rory Lewandowski is an OSU Extension Agriculture & Natural Resources educator and may be reached at 330-264-8722.