Early-Season Soybean Management for 2019

Average Illinois soybean yield first exceeded 50 bushels per acre in 2004, when it was 50.5 bushels. It was 51.5 bushels in 2010, and 50 bushels in 2013. Over the five years beginning in 2014, it was 56, 56, 59, 58, and, in 2018, an astonishing 65 bushels per acre. Yield in each of the past five years was above trendline, which is a first—the longest stretch of above-trendline yields in the previous 30 years was for three years. In each of the three years 2004, 2014, and 2018, soybean yield exceeded the previous record by about 10 percent. Illinois corn yields were record-high in each of these three years as well, showing that both crops tend to respond similarly to unusually good growing conditions.

Variety selection and maturity

Most people have already selected varieties for 2019. There are a lot of good varieties and a lot of information available on their performance. The University of Illinois soybean variety trials are only a small part of this information, but there are comparisons there that might not be available from other sources. Still, seed companies remain the primary source for information about the varieties they sell, and finding topnotch genetics shouldn’t be too difficult.

One issue that continues to attract interest is how varietal maturity affects yield. In the UI variety trials, entries at each location are separated in roughly equal numbers into two sets: one with longer- and one with shorter-maturity varieties. These sets are planted in separate trials, mostly so the early-maturing ones can be harvested first if a long delay will compromise their performance. Averaged across 5 regions and 13 sites in 2018, the “early” varieties averaged 74.8 bushels per acre, and the “late” ones averaged 73.5 bushels per acre. So across a range of maturities within and among regions running from north (average MG 2.7) to south (average MG 4.2) in Illinois, maturity was not consistently related to yield. We might want to choose a mixture of earlier and later varieties to spread harvest some, but should concentrate more on yield potential than on maturity.

Planting date

We continue to hear a great deal of talk about the need to plant soybeans early in order to get high yields. This is hardly a new discovery: ever since we saw major improvements in seed quality and seed treatments several decades ago, we have known that early-planted soybeans were capable of emerging without the need to wait until soils had warmed up to 55 or 60 degrees before planting.

In recent years some have taken “early” planting to an extreme, however, with claims that soybean planting should some before corn planting, as early in March if possible. Figure 1 summarizes the results of 26 planting-date trials conducted in central and northern Illinois between 2010 and 2016. Our target planting dates were in mid-April and then about every two weeks to early June. Planting dates were converted to days after April 1, and yields within each trial to percent of maximum yield for that trial.

Figure 1. Combined results over 26 soybean planting date trials in central and northern Illinois from 2010 through 2016.

We saw little yield decrease when planting was done by May 1 (day 31), about 7% lower yield if planting was on May 15 (day 46), and 14% lower yield if planted on June 1 (day 62). While we did not plant before April 10 in any of these trials, the fact that yields were no higher from planting on April 15 than on April 30 shows that the “early planting” advantage is generally maximized if planting can be done by the end of April.

It’s not clear what advantage there might be in planting soybeans in March, or even, as some did in 2017, in February. Emerged soybean plants are can tolerate low temperatures, with the exception of the few days when the “hypocotyl hook” appears above-ground but before it straightens (in response to light hitting its upper surface) to pull the cotyledons above the soil surface. If frost hits at this point, the exposed hook (stem tissue) can be killed, which kills the seedling. Seedlings are usually in slightly different stages down the row, so frost at this stage will seldom kill all of the seedlings, but it can certainly thin them out.

Soybeans planted in March 2018 encountered cold, wet conditions, including several snow events, during the month after planting. While any emergence under such conditions testifies to the toughness of soybeans, it’s likely that many of these were replanted. Besides stand loss, soybean plants exposed to low temperatures early in the season typically stay short, and often do not yield as much as later-planted soybeans. This shortening might have been partially reversed by increased internode elongation during very warm May weather in 2018. Still, soybeans planted in late April in 2018 also made rapid growth in May and had better stands, so probably yielded more than those that survived March planting. The goal of planting early is not to have the crop survive, but to have it yield more. Low stands and short plants aren’t generally conducive to highest yields, and issues with crop insurance coverage may be another disincentive. There certainly seems to be little reward for taking the risk of planting very early.

Should later-maturing varieties be planted first in order to take maximum advantage of the longer time in the field? There’s no problem with doing that, although early planting moves up harvest date some, so works counter to the goal of spreading harvest time by using different maturities. In 2018 we ran a trial at Urbana, supported by a seed company, to see how varietal maturity affected response to planting date. The first planting date was April 26, the last was June 6, and varieties ranged in maturity from MG 2.3 (very early for this location) to MG 3.6, which is a little later than average for this location.

Figure 2. Response to planting date by five soybean varieties differing in maturity. Data are from a trial conducted at Urbana, Illinois in 2018.

For all but the earliest-maturing variety in this trial, the planting date response was almost perfectly linear, with the loss of nearly 7/10ths of a bushel per day of planting delay—a total of more than 27 bushels—over the 41 days from the first to the last date (Figure 2). This loss rate accelerated a little for the latest-maturing variety between May 24 and June 6. The earliest-maturing variety lost only 17 bushels from first to last planting, but only because its yield at the earliest date was so much lower than yields of the later-maturing varieties.

The month of May 2018 was much warmer than normal, and this got the soybean plants off to a very fast start. Warm nights are conducive to early flowering, and this was especially notable in 2018. In the early-planted crop, first flowers appeared in early June, well before the longest day of the year, and unlike the interruption of flowering that often takes place under normal night temperatures for about a week before and after the longest day, flowering was early and continuous in 2018. As a result, nearly half of the Illinois soybean crop was flowering by July 1. The warm May probably affected the yield response to planting date as well; with warm temperatures, early-planted soybeans as fast as late-planted ones, and this widened the developmental gap between the different plantings.

Planted on April 26, the earliest variety reached first flower on June 9 and matured on August 28, compared to June 15 and September 17 for the latest-maturing variety. When planted on May 24, the earlier and later varieties flowered on June 15 and July 2, and matured on September 12 and September 25, respectively. So when planted late, both varieties flowered very early in their life cycles, both spent less time in reproductive stages than when they were planted early, and they ended up yielding about the same. While in this case it’s accurate to say that the later-maturing variety benefitted more from early planting, that’s only because the early-maturing one was physiologically less able to use the longer growing period allowed by early planting to produce high yield.

Seed and seeding rate

Seed quality as measured by the standard warm germination results is probably good in most cases this year, but there were enough issues related mostly to harvest time weather last fall that vigor—the ability to produce good stands under stressful soil conditions—may be lower than in some previous years. Vigor is commonly measured by the “cold test”, which consists of keeping the seed in soil at 50 degrees for several days followed by a standard warm germination test. Cold test results can be somewhat hard to interpret, but most of the time, actual emergence is higher than the cold test score. Many companies take cold scores and might be willing to share them for seed lots this year.

Although promoting low soybean seeding rate for high yields seems to have cooled a little, some still contend that planting 100,000 seeds per acre is enough. We have conducted small-plot seeding rate trials each of the past four years at six or seven sites per year around Illinois. We plant rates of 50, 100, 150, and 200 thousand seeds in replicated trials, and report yields by actual plant stands. Figure 3 below shows the results from the 2018 trials. Plant stands as percentage of dropped seeds were high in 2018, and yields were high to very high. Optimum stands ranged from 86,000 to 201,000 plants per acre.

Soybean seeding rate responses at seven Illinois sites in 2018. The yellow triangle on each curve marks the optimum stand, where added seed just paid for itself in higher yield.

The wide ranges of optimum plant stands and yields in 2018 were not unusual; across all 27 trials over the past four years, optimum stands ranged from 50,000 to 201,000, and yields at optimum stands from 53 to 90 bushels per acre, with no discernible correlation between yields and stands (Figure 4). How do we deal with such variability across sites? We certainly can’t plant enough seeds to make sure we never have too few plants—that would take planting more than 200,000 seeds per acre. With no correlation between yield and seeding rate, we also can’t reasonably adjust seeding rate by expected yield, and we can’t know actual yield. A reasonable approach is to cover most cases by planting to produce stands of about 120,000 plants per acre, which is close to the stand needed to maximize return to seed (gross return minus seed cost) in the majority of responses.

Figure 4. Optimum plant stands and yields at those stands across 27 sites in Illinois, 2015-2018.

How many seeds do we plant if we want to end up with 120,000 plants? Over the trials reported here, plant stand as a percentage of dropped seeds averaged in the low 80s for the first three years, and was close to 100% in 2018. We normally divide the desired stand by the warm germination (percentage expressed as a fraction, as in 0.95), and then by a percentage that, based on soil conditions and seed placement, we reasonable expect to produce a stand. Planting seed with high germination percentage into good soil conditions with a planter that places seed well, it may be reasonable to expect 80% establishment. If we want 120,000 plants, that would mean planting 120,000 ÷ 0.80 = 150,000.

Should we raise seeding rates to avoid having to replant if we’re planting into cool soils the last week of April? We may want to raise them a little if the cold test percentage is marginal. But the most common cause of having to replant is heavy rains after planting that leaves seeds without oxygen in the soil, causing seed death and very low stands. In few cases like this does raising the seeding rate increase the stand enough to avoid replanting.


On soils heavier than loam in texture, it is unlikely that adding nitrogen fertilizer at planting, or during the season, will increase yields. On lighter soils, adding urea at planting might increase early growth and yields, but the chances of this happening are not high. There has been some data from Iowa and Indiana suggesting that adding sulfur might help soybean yields, especially (but not only) in lighter soils. As with N, we don’t have good guidelines on when S might be needed, but we do not think that the need is routine. Ammonium sulfate broadcast at planting at a rate of about 20 lb. of S (83 lb AS) can supply both N and S, but is not inexpensive. Keep in mind that most of the outstanding soybean yields in 2018 were produced without adding N, S, or other products not known to be needed for high soybean yields.

Register now for Tar spot Webinar, March 1

3/1/19 at 9:00 am CST



Join Dr. Nathan Kleczewski from the University of Illinois Extension  for an update on Tar spot in corn.  This disease was first observed in the United States in 2015 in Northern Illinois and Indiana.  In 2018, the disease significantly affected corn production in the Midwest and Florida.  What is tar spot of corn?  How does it work?  What is our current understanding of this disease and its management?  These and other questions will be addressed through this free webinar.


Registration is free, but capped at 100 participants.


To register for this meeting, click the following link: https://web.extension.illinois.edu/registration/?RegistrationID=19924


We look forward to seeing you March first!

Setting the record straight on Tar Spot

Remember that game of telephone we played as kids?  One person says something in to the ear of another and after passing through 10 people or so the starting message, “I like peanut butter” ends up as, “John licks turtles.”  Sometimes that can happen with information pertaining to plant diseases.  Lately there have been some interesting things said about tar spot on corn in the community.  To help clarify, and set the record straight, I published an article on my blog, which can be accessed here.

Corn Hybrid Response to Tar Spot

Hybrid resistance is a key component for managing many plant pathogens.  To access a new sheet on hybrid response to tar spot in corn click the following link: Corn Hybrid Response to Tar Spotfin.docx.

We are currently rating multiple variety trials in affected areas across states to generate more hybrid-specific data.  More information will be available soon.

Tar Spot in corn- requesting your help

Tar spot is a relatively new disease in corn.  It was first described in Illinois and Indiana in 2015, and was first located near DeKalb.  Tar spot has been detected to some degree in Northern Illinois each year since.  However, typically infections are sparse and the disease does not come in until later in the season.  Consequently, yield loss due to this disease has been minimal, and the disease mostly considered an oddity.

However, in parts of Latin America, where the disease is known as Tar Spot Complex, severe yield losses can occur.  In this case, two pathogens are involved.  One fungus produces the black tar spots we typically see, and another produces toxins that can cause varying degrees of foliar  blight and necrosis.  Our colleagues at CIMMYT in Mexico are currently working on identifying the toxins involved and how they may relate to  virulence.  It is important to note that there is very little known about tar spot complex, how the pathogens interact with oneanother, the epidemiology of the disease, and how the pathogens interact with their corn host.  In addition, it is possible that this disease may act differently in Midwest production systems, as hybrid genetics, production practices, and environments differ from those in Latin America.

Tar Spot on corn with Black raised “bumps” and small necrotic fisheye symptoms. N Kleczewski and J Donnelly

This season we have seen this disease take off in Northern Illinois, as well as Southern Wisconsin, Michigan, and parts of Indiana.  Symptoms vary from from the traditional black raised bumps, to bumps with necrotic fisheye lesions, to spots on leaves that blight and drydown.  Some fields have light infection, whereas others have over 30% leaf severity through the highest leaf of the hybrid.   Early this summer, prior to this outbreak,  we started working with colleagues in other states and CIMMYT  to better understand the tar spot pathogens and improve our abilities to detect and manage this disease if needed.  One item that we need for this project are samples.  If you have fields with symptoms of tar spot, particularly those with necrosis associated with the lesions, please send care of Dianne Plewa at the University of Illinois Plant Disease Clinic.  The website with address and contact information is located at the following address: https://web.extension.illinois.edu/plantclinic/  Please include the county of origin, if a fungicide was applied, and the hybrid, if possible.

In addition, we are working to assess potential variety response and yield impacts of this disease.  If you would like to participate in the effort, please contact me at 217-300-3253 or email me at nathank@illinois.edu.  I also can be reached on Twitter @ILplantdoc

Spray Decisions for Frogeye Leaf Spot on Soybeans

Many people have asked about the need to make a fungicide application for frogeye leaf spot on soybeans this season.  I have posted a new article on the Illinois Field Crop Disease Blog which reviews this pathogen, how it works, and some new tools that may help you with these important decisions.  Find the article by clicking here.

Is the 2018 soybean crop as good as it looks?

If the appearance of the soybean crop going into late July predicts how it will yield, the 2018 crop in Illinois is going to be a high-yielding one. The crop in Illinois was rated at 78% good + excellent (G+E) as of July 22. Conditions across the US soybean growing regions are somewhat variable, but the 2018 crop is in good condition overall.

As I did with corn in the Bulletin on July 6, I examined Illinois soybean crop ratings in the second half of July over the past decade to see how well they predict yield. The drought year 2012 was in a category by itself, with a G+E rating of less than 10% by late July. Ratings were only about 50% G+E in 2015, but in six of the past ten years—2008-2011, 2013, and 2017—ratings were around 60% G+E in late July. In 2014, 2016, and now in 2018, ratings were high, at 75 to 80% G+E.

With a few exceptions, soybean crop ratings have tended either not to change much after mid-July or to drift up slowly. Exceptions included 2008, when crop conditions rose by about 20 points from late July to mid-August, and 2011, when ratings dropped about 20 points during the same period. In 2017, ratings drifted down after June, from 70% G+E in early July to less than 60% by late August.

Illinois soybean yields were 50 bushels per acre or less in years with late July crop ratings of 60% G+E or less, with the exception of 2010, when the crop yielded 51.5 bushels. In both 2015 and 2017, mediocre late-July ratings failed to predict high yields, of 56 in 2015 and 58 in 2017. In 2014 and 2016, high ratings did predict high yields, of 56 and 59, respectively. Overall, high soybean crop ratings by late July tend to predict high yields, while low to medium ratings can sometimes be offset by August weather, resulting in average or even above-average yields. Because high crop ratings in late July predict high yields, we expect high soybean yields in 2018.

Another factor favoring soybean crop prospects this year is the rapid pace of crop development. Planting did not start early this year but it was finished early, and with May and June warmer than average, the crop was off to the races, with 44% of the crop flowering by the end of June. This continued into July, with 44% setting pods by July 15 and 66% setting pods by July 22. The 5-year average shows 24% of the crop setting pods by July 22, and about 50% by August 1. So the 2018 crop reached 50% podsetting about two weeks earlier than normal.

An early start to podsetting should be favorable, as long as there’s enough water to keep the crop in good shape. The amount of time between podsetting and loss of green leaf color (both recorded by NASS) estimates the duration of the seedfilling period, which is well-correlated with yield. On average, the Illinois reaches 50% leaf color change by about September 15, or about 45 days after 50% podsetting. The 2018 crop needs only to fill seed through the end of August to reach 45 days. With somewhat higher temperatures and longer days in August than in September, having seedfilling begin and end two weeks early should be favorable for seedfilling rate and yield.

We don’t very well understand what signals the end of seedfilling, but both temperature and daylength have some influence. The number of pods that are filling, maturity rating of the variety, and other factors have some effect as well. If temperatures remain normal and the crop has enough water, the need to have days shorten to a certain length before seedfilling stops should mean a somewhat longer filling period this year; this should add yield. But with the early start, seedfilling should be adequate for good yields this year even if it ends by early September.

Other positive signs for the soybean crop this year are the excellent plant stands in most fields, the excellent condition and color of the canopy, and the large number of pods already formed and still forming. The canopy is outstanding in most fields now, and we expect it to take on a darker green color as podfilling gets up to full speed over the next two weeks. I have not heard much about fertilizer nitrogen application this year, but with the canopy in such good shape, it seems unlikely that the crop will need extra N. A fair number of fields have received fungicide, and probably insecticide as well, though we can probably call the “race” between canopy development and insect feeding in favor of the crop this year.

Soybean plants have grown tall due to warm temperatures and adequate water in most fields. Plants are at or close to their final height in fields where seedfilling has gotten underway. Periods of drier weather and warm temperatures have provided enough competition for water to keep the canopy in most fields from getting heavy enough to cause internal shading that can limit pod formation or seedfilling rates. We can probably expect some lodging, especially in 30-inch rows where plants are already tall. Moderate lodging as pods fill is a signal that pods are heavy, so is not a concern, especially if plants just “lean” without affecting light interception.

Counting pods and seeds on plants in mid-season is neither a lot of fun nor an overly accurate way to estimate soybean yield potential. But with pods setting early this year, it’s a little easier to see how yield potential is shaping up. Pod numbers and number of seeds per pod appear to be very good in most fields. We’d like to see 4-5 pods filling at each middle node, and 30 to 50 pods per plant. A field with 130,000 plants per acre, 40 pods per plant, 2.8 seeds per pod, and 2,700 seeds per pound at harvest projects a yield of 90 bushels per acre. While we don’t expect such yields in most fields, we have seen yields this high or higher in some fields in each of the past four years. Based on what we see now, we expect to see this in some fields in 2018 as well.

Ewing Demonstration Center Celebrates 50 years of Continuous No-till Research at Agronomy Field Day on July 26

The University of Illinois Extension will host the Ewing Demonstration Center Agronomy Field Day on Thursday, July 26, 2018 at 9 a.m.  Every growing season presents challenges to production, and this year is no exception!  We are happy to host this summer field day to share with local growers current, ongoing agronomy research in southern Illinois, including cover crop trials on corn and soybeans, nitrogen management in corn, weed management in soybean, and our continuous no-till field, now in its 50th year of continuous no-till production.

We are highlighting our 50th year of continuous no-till production in our field day this year.  This no-till trial area was established in 1969 by George McKibben, the “Father of No-Till”, long-time agronomist and researcher at the Dixon Springs Ag Center in southern Illinois.  This plot has been cropped utilizing no-till production of corn and soybeans ever since.  The “zero-till” system as it was first called, was researched to “save the soil” that was lost over the many years of intensive tillage required to raise grain crops on the sloping hills of southern Illinois with the planting equipment available at the time.

In honor of this milestone, we will have the original “zero-till planter” on display.  This planter was modified and built in the early 1960s at the Dixon Springs Ag Center and used there and also at the Ewing Demonstration Center and other research sites.  The demonstrated success of this zero-till planter and production system was one of the inspirations that led companies like Allis-Chalmers and John Deere to start engineering and producing no-till planting equipment.  Also, joining us for the field day will be Donnie Morris, retired farm mechanic and engineer who built this planter, along with other retired Extension advisors and educators that worked at the Ewing Demonstration Center over the years.


The topics to be discussed at Field Day include:


Looking Back at 50 Years of Continuous No-till

  • Current and Retired Staff, University of Illinois

Insect Management in Corn and Soybean

  • Nick Seiter, Research Assistant Professor, University of Illinois

What We Have Learned After 48 Years of Continuous No-till

  • Ron Krausz, Manager SIU Belleville Research Center
  • Sarah Dintelmann, Undergraduate Assistant ,Weed Science, SIU

Managing Cover Crops in Corn and Soybean

  • Nathan Johanning, Extension Educator, University of Illinois

Intro to Corn Genetics:  Why is Sweet Corn Sweet?

  • Talon Becker, Extension Educator, University of Illinois


Please join us for Agronomy Field Day to help celebrate this milestone in crop production!  The field day is free and open to anyone interested, and lunch will be provided.  Certified Crop Advisor CEUs will also be offered (Soil & Water – 2.0; IPM – 0.5, Crop Management – 0.5).  The Ewing Demonstration Center is about 20 minutes south of Mt. Vernon located at 16132 N. Ewing Rd; Ewing, IL 62836, on the north edge of the village of Ewing, north of the Ewing Grade School on north Ewing Road.  Watch for signs.

To help us provide adequate lunch and materials, please RSVP to the University of Illinois Extension Office in Franklin County at 618-439-3178 by Tuesday, July 24.  For additional information on the field day, contact Marc Lamczyk at the Franklin County office or lamczyk@illinois.edu.

Tips on making fungicide application decisions in field crops

We are at that time in the season where many people will be making final decisions regarding fungicide applications in soybeans and corn.  I wrote an article with tips and other items to consider when making fungicide decisions and on farm trials on the Illinois Field Crop Disease Blog, which can be found by clicking HERE.