Calling Illinois Soybean Growers-Again

In January I posted about the large project we are part of, funded by the North Central Soybean Research using soybean checkoff funds, to gather information on some 500 soybean fields in Illinois for each crop year from 2014 through 2017. The response has not been as enthusiastic as I had hoped, so I’m again calling for help on this. With 10 million acres of soybean in Illinois, 500 fields is less than a quarter of a percent of fields. And since we’re requesting information on up to 4 fields per grower, having only 2 or 3 producers in each soybean-growing county do this would get it done.

The most useful way I’ve heard this project described is as a “search to find what we should work on next” with regard to soybean research. The goal is to have thousands of fields in a large database, then to see how soil, weather, and management interact to produce yield.

To help, download the forms and other information at http://go.illinois.edu/soy-survey – if you want the fillable (PDF) forms please email me or email soyncsrp@illinois.edu The forms can be emailed back or printed and returned by mail.

We will provide a $50 gift card as an incentive for people to fill out forms. The gift card request form is included in the group of forms, and can be returned with them. It would be great if FFA and college students (maybe those on spring break) could get experience taking part in a scientific study and also earn a reward for their efforts.

If you have questions about this, or if you’d like forms mailed instead of downloading them, please contact soyncsrp@illinois.edu or me by email.

Thanks in advance for your help.


Extension Bi-State Crops Conferences in and near Western Illinois

Newer and longer-term partnerships between personnel in Illinois and personnel in Missouri and Iowa have resulted in several bi-state crops conferences to be held during January 2017 in Western Illinois or Eastern Iowa.

 

Friday, January 6, 2017: Bi-State Crop Advantage Conference, Burlington, IA, 8:30 AM – 4:00 PM

Location: Comfort Suites, 1708 Stonegate Center Drive, Burlington, IA.

Hosts: Iowa State University and University of Illinois Extension

More Information: Click here to access the flier.

Online Registration: Click here to register

 

Friday, January 27, 2017: Bi-State Crop Advantage Conference, Davenport, IA, 8:30 AM – 4:00 PM

Location: Rhythm City Casino Resort, 7077 Elmore Ave., Davenport, IA

Hosts: Iowa State University and University of Illinois Extension

More Information: Click here to access the flier.

Online Registration: Click here to register.

 

Friday, January 27, 2017: Western Illinois-Northeastern Missouri No-till Crop Management Conference, Quincy, IL, 8:45 AM – 2:00 PM

Location: John Wood Community College, 1301 S. 48th St., Quincy, IL

Hosts: University of Illinois and University of Missouri Extension, Illinois and Missouri NRCS

More Information: Click here to access the flier.

Online Registration: Click here to register.


Nitrogen on Corn in 2016: A First Look

The 2016 cropping season was a good one in Illinois, with planting a little ahead of normal and good May moisture and temperatures to get the crop off to a good start. June was warm and, in most parts of Illinois, drier than normal; parts of western Illinois received less than an inch of rainfall for the month. Temperatures and rainfall returned to normal in July and August, though there was the usual variability from region to region, including much-above-normal rainfall in the southern end of the State.

With good May soil conditions, mineralization got off to a fast start, and the crop in most fields was dark green by the end of May and starting to grow rapidly. Without N loss conditions in June, N from both fertilizer and mineralization stayed in the rooting zone, and N availability to the crop was outstanding. Even no- or low-N strips stayed dark green in trials into the middle of June, much later than we normally see N deficiency developing.

The retention of N in the soil and its availability to the crop carried through the season to diminish the need for fertilizer N. Figure 1 shows a response to N in an on-farm trial in DeWitt County, Illinois. Not only did about 150 lb. of N maximize yield at 230 bushels per acre, but it made almost no difference whether the N was applied in the fall or in the spring. We know from our N tracking that most of the N was in the nitrate form by the time crop uptake started in late May; we can see here that in the absence of N loss (wet) conditions, nitrate stays in the soil and is available for plant uptake just like ammonium.

Figure 1. N responses from fall- and spring-applied anhydrous ammonia in an on-farm trial in DeWitt County, Illinois in 2016. Optimum points are the N rate and yield at the point where the last addition of N provides just enough yield increase to pay for that N.

Figure 1. N responses from fall- and spring-applied anhydrous ammonia in an on-farm trial in DeWitt County, Illinois in 2016. Optimum points are the N rate and yield at the point where the last addition of N provides just enough yield increase to pay for that N.

 

Dan Schaefer of IFCA coordinated dozens of on-farm trials similar to the one shown in Figure 1. Some had fall versus spring N timing comparisons, some had all early versus some early plus sidedress, and others just compared yields at different N rates. Figure 2 shows results from 26 trials conducted across central Illinois in 2016.

 

Figure 2. N responses from 26 N rate trials in corn following soybean in central Illinois, 2016. Each line connects the data points from one trial, and the optimum points (triangles) are calculated from curves (not shown) fitted to the data. The MRTN points are calculated as the yield at 175 lb N/acre, which is the MRTN (optimum N rate) calculated for central Illinois corn following soybeans at a N to corn price ratio of 0.1 ($0.375/lb. of N and $3.75/bushel of corn.)

Figure 2. N responses from 26 N rate trials in corn following soybean in central Illinois, 2016. Each line connects the data points from one trial, and the optimum points (triangles) are calculated from curves (not shown) fitted to the data. The MRTN points are calculated as the yield at 175 lb N/acre, which is the MRTN (optimum N rate) calculated for central Illinois corn following soybeans at a N to corn price ratio of 0.1 ($0.375/lb. of N and $3.75/bushel of corn.)

In 2015, high N loss conditions and damage from standing water resulted in high optimum N rates. In 2016 we found just the opposite: Figure 2 shows that relatively low rates of N were needed to maximize yield in nearly every case. Of the 26 trials, only five had an optimum N rate higher than the MRTN rate, and on average across trials, only 150 lb. of N was needed to produce an average yield at the optimum N rate of 225 bushels per acre. Some like to calculate “efficiency” of (fertilizer) N by dividing yield by N rate; here, we calculate a very high efficiency of 2/3rds of a lb. of N per bushel of yield, or 1.5 bushels per lb. of N used.

We ran a new study at a number of sites this year to compare the application of N rates at planting to keeping 50 lb. of N back and applying it dribbled next to the row at tasseling. Figure 3 shows the results of the corn following soybean trial at Urbana.

 

Figure 3. Response to N applied as UAN at planting (early) compared to applying all but 50 lb. of N at planting them dribbling the remaining 50 lb. next to the row at tasseling.

Figure 3. Response to N applied as UAN at planting (early) compared to applying all but 50 lb. of N at planting them dribbling the remaining 50 lb. next to the row at tasseling.

Responses to late-split timing of N at other sites were all similar to that in the trial shown in Figure 3. We had three corn following corn trials and four corn following soybean trials, and in none of them did keeping back 50 lb. of N to apply late provide a benefit to either yield or return to N; that is, late-split application did not pay the added application cost. This makes sense given the low N loss conditions in 2016. We would expect to see some loss and possible response to late supplemental N following a wet June, though we did not see much response to a single treatment (150 lb. N early versus 100 early and 50 at tasseling) in 2015.

We’re seeing N “at its best” in 2016; it was there in abundance when the crop needed it, and adding the supply of N from soil organic matter meant that the crop needed less fertilizer N than it has typically needed, even at high yield levels. We can’t depend on this to happen in 2017, but we see clearly that the common idea that “high yields require high N rates” often does not hold true. There is certainly no need to raise rates for next year, and fields that received more N than was needed in 2016 (according to N response curves that is probably most fields) might have added to the pool of soil N that can be tapped by the 2017 crop, whether that’s corn or soybean. Keep in mind, though, that what we saw in 2016 was mostly a response to the (June) weather and crop off to a good start; we will need to watch how things develop in the spring of 2017 to know if we’ll have a repeat.

 


2016 Tar Spot again found on corn in Northern Illinois

Corn leaf samples from LaSalle county have been positively identified by the University of Illinois Plant Clinic to be infected with Tar Spot Phyllachora maydis.  Commercial Agriculture Extension Educator Russ Higgins found the disease while field scouting.  The fungal leaf blight was identified in numerous northern Illinois and northern Indiana counties in 2015.

Tar Spot has distinctive signs and symptoms. The fungal fruiting body, called an ascomata, looks like an actual spot of tar on the leaf.  Lesions are black, oval to circular.  They can be small flecks of about 1/64” up to about 5/64”.   The lesions can merge together to produce an affected area up to 3/8”.  If you run your finger across the leaf you will feel tiny bumps.

Picture 1. Distinctive black fruiting bodies of Tar Spot on corn leaf 2016. Photo courtesy of Russ Higgins, University of Illinois Extension

Prior to 2015, Tar Spot was known to occur only in cool humid areas at high elevations in Latin America.  Tar Spot can form a complex with another fungus. The 2 fungi that cause ‘Tar Spot disease complex’ on corn are  Phyllachora maydis and Monographella maydisWhen  Monographella maydis is in association with  Phyllachora maydis  the complex has been demonstrated to cause economic yield losses in Latin America. Phyllachora maydis alone is not known to significantly reduce yield.  When the two are in combination a distinctive symptom is seen.  The black Tar Spot will be surrounded by a tan lesion so the two together resemble a ‘fish-eye’.

Other pathogens may be confused with Tar Spot, especially the overwintering teliospore (black) phase of corn rust.  Also, there are many fungi, called saprophytes that feed on dead corn tissue and form black splotches on the leaves.

To date only one of the pathogens, Phyllachora maydis, has been found in IL in 2015 and 2016, and IN in 2015.  If you suspect Tar Spot please submit a sample to The University of Illinois Plant Clinic.  We are cooperating with USDA-APHIS-CAPS to get a comprehensive idea of distribution in the state.  Illinois producers can participate at no cost, see how at this link https://uofi.box.com/s/bizu6oz3re35v9boif784nz4zvy85gjc

 


New bacterial leaf disease “Bacterial leaf streak” identified in one northern Illinois County

Extension Staff Join with other Agencies to Survey Illinois for New Corn Disease 2016: The USDA just announced the presence of Bacterial leaf streak in corn, as determined by recent surveys of the Corn Belt states.  In Illinois, a cooperative survey was organized with APHIS-PPQ (Animal Plant Health Inspection Service), IDA (Illinois Department of Agriculture), CAPS (Illinois Natural History Survey’s Cooperative Agricultural Pest Survey) and University of Illinois Extension to provide a rapid response to determine distribution.

In a short time window, our surveyors examined randomly selected fields in transects across 68 of Illinois’s 102 counties. They looked for Bacterial leaf streak symptoms in approximately 340 fields across the state.  Leaves with suspicious symptoms were collected and have been sent to a USDA laboratory for evaluation.  The Extension surveyors consisted of volunteers from the Commercial Agriculture, Small Farms and Local Foods and the Energy and Environment teams.

One positive sample of Bacterial leaf streak was found in DeKalb County, IL and identification was verified by the USDA yesterday.  This is the only county in Illinois that has been verified to have the disease.  So far, Bacterial leaf streak has been identified in 9 states:  Colorado, Iowa, Illinois, Kansas, Minnesota, Nebraska, Oklahoma, South Dakota, and Texas, figure 1.

Figure1: Illinois surveyed counties for Bacterial leaf streak 2016

Bacterial leaf streak is caused by the pathogen Xanthomonas vasicola pv. vasculorum. The disease causes the formation of linear lesions between the veins on a corn leaf. The lesions look similar to gray leaf spot (GLS) symptoms. GLS lesions tend to be shorter, more rectangular and stay within their veinal borders. Bacterial leaf streak lesions are more irregular, often thinner and longer,  will “bleed” over the veinal border and may have a halo when held up to the light.

Xanthomonas1

Picture 1. Foliar symptoms of Bacterial leaf streak showing long lesions with wavy margins and halo visible with back-lighting. Photo courtesy of Nicole E. Furlan USDA-APHIS-PPQ

In many Great Plains states that have found the disease, symptoms first appear on the lower leaves and infection progresses up the plant. Typically these fields have been under pivot irrigation.  However later infections may occur and show up primarily in the upper canopy, as was the case for the positive DeKalb county sample.  There is currently very little known about this disease. Further research is needed to develop a complete understanding of this disease, its impact and strategies for long term management.  However, APHIS notes it is not believed to present a health risk to people or animals.

Picture 2: Late foliar symptoms of Bacterial leaf streak showing long lesions.  Photo courtesy of Scott Schirmer Illinois Department of Agriculture, State Plant Regulatory Official.

Picture 2: Late foliar symptoms of Bacterial leaf streak showing long lesions. Photo courtesy of Scott Schirmer Illinois Department of Agriculture, State Plant Regulatory Official.

Since this is a bacterial disease, fungicides cannot be expected to control or suppress this disease. Crop rotation and tillage are the best short-term management strategies if the disease is present in a field.  Differences in varietal susceptibility may point the way to sources of resistance.

If you suspect Bacterial leaf streak, submit a sample to the University of Illinois Plant Clinic http://web.extension.illinois.edu/plantclinic/ We would like to get a comprehensive idea of distribution in the state. For more information on Bacterial leaf streak,  biology, symptoms, or management, please visit: http://cropwatch.unl.edu/bacterial-leaf-streak from University of Illinois alumna Dr.Tamra Jackson-Ziems, Nebraska Extension Plant Pathologist, and http://broderslab.agsci.colostate.edu/corn-bacterial-leaf-streak/.

Authors: N. Dennis Bowman and Suzanne Bissonnette


“Tip-back” and the 2016 corn crop

Although my post last week reflected the current optimism about yield prospects for the 2016 Illinois corn crop, there has been some recent discussion about unfilled ear tips and whether or not this might mean lower yields than the appearance of the crop leads us to believe.

Corn ears with kernels missing at the outer end of the ear are often said to have “tip-back.” The term is a little obscure, but the idea is that the end of the cob has been exposed by lack of kernels there, and that something happened to cause the ear to adjust its kernel number downward so it won’t have as many kernels to fill.

The missing kernels can be aborted kernels – ones that were fertilized but stopped developing – or can be kernel initials that weren’t fertilized due to problems with the pollination process. Low sugar levels in the plant before, during, and after pollination are often associated with such loss of kernels.

Because kernel number is closely related to yield, missing kernels on an ear suggest to many people that yield has been lost. Drought stress, loss of leaf area to hail or disease, or lack of nitrogen all result in stress that lowers photosynthesis and so decreases the sugar supply. So we associate low kernel numbers with stress. If different hybrids show different amounts of tip-back, this is taken as an indication of their tolerance to stress.

While low kernels numbers per acre and low yields do go together, it’s important in a year like this to consider the overall condition of the crop and to focus on how many kernels are present before worrying about how many kernels seem to be missing. We often see some amount of tip-back even in good years, and this may have no effect on yield if kernel numbers are still high.

As an example, under outstanding pollination conditions in 2014, we saw almost no tip-back; ears were filled out to the very end of the cob. There was much more tip-back in 2015, but kernel counts per acre and yields were as high in many areas in 2015 as in 2014. While we don’t think that having some tip-back is necessary to show that the ear had “extra” room in case it was needed it, it’s much more common to see some tip-back than to see none, and we don’t consider tip-back to be a problem if kernels numbers are high.

What matters for yield is the number of kernels per acre that fill, along with the ability of the crop to fill them completely. So 34,000 ears each with 16 rows of kernels and 35 kernels per row should produce yields in the vicinity of 220 bushels, even if most cobs have “room” on the end for another 50 or 100 kernels. At high yield levels when all of the nutrients the plant produces go to fill kernels, having more kernels may mean that kernels stay smaller, and yield may not change much.

In looking at some of our corn on South Farm on August 3, I saw more variability in kernel number and some smaller ears than I expected. In one field planted at about 36,000 seeds on April 20, plants were about 10 ft. tall but stalks were small in diameter and ear placement was high and somewhat variable. Figure 1 shows some ears in this field. This crop came up well and has had the dark green leaves and uniform appearance that most fields in the area have shown since emergence. But there are only about 375 kernels per ear on average, and if kernels fill to normal weight, yield will be around 160 bushels per acre. Ears show a lot of tip-back, and having silks still attached suggest that most of this resulted from failure of pollination. Kernels were in the late milk stage which is in line with planting date, but otherwise the crop has the appearance of corn that was planted late.

Figure 1. Ears in corn planted at 36,000 per acre on April 20.

Figure 1. Ears in corn planted at 36,000 per acre on April 20.

In another field with similar soil planted at the same time with slightly lower population, plants were not quite as tall, stalks were larger in diameter, and ears were more uniform in both placement and size (Figure 2). These ears show a small amount of tip-back, but with an average of about 600 kernels per ear, this field should yield 225 bushels per acre or more.

Ears in corn planted at 34,000 on April 22

Ears in corn planted at 34,000 on April 22

There are no obvious reasons why similar fields planted at about the same time should have such different kernel numbers and yield potential. The hybrids are different, but the field with lower yield potential has a number of different hybrids and most seem to show some degree of the same problem.

Even when plants emerge well and looked uniform in size and canopy color during vegetative growth, variability in ear size and placement suggests that plant-to-plant competition began early and increased during vegetative growth, eventually showing up as non-uniform ear development and lower kernel numbers. We can only speculate about how this might have happened, and why fields differ as much as they do. With the exception of a couple of cool periods in May, temperatures in May and June were warm and there was a lot of sunshine. Rainfall both months was near normal, but the latter half of June was dry, which could have meant more underground competition.

It appears that the crop used a lot of resources to grow the plant, including roots as they grew deeper during dry weather in the weeks before pollination. Uniformly warm air and soil temperatures and rapid growth during that period might have meant some diversion of sugars away from ear growth and kernel set. It’s also possible that uptake of water was slightly lower in some soils due to texture or root growth and uptake, and that the crop in such soils experienced a little more stress.

Although we can’t do anything to change kernel numbers now, it is worthwhile to visit each field to note kernel number and other plant characteristics that can help explain what happened in different fields. While the Illinois corn crop condition overall remains good, some fields may have disappointing kernel numbers even on plants that continue to look very good. Note which hybrids show this, but given that this may be a one-time phenomenon, be cautious about discarding hybrids, especially those that have been top-yielding in the past.


2016 Ewing Agronomy Field Day – July 28

We invite everyone to the University of Illinois Extension Ewing Agronomy Field Day Thursday, July 28, 2016 starting at 9 a.m. at the Ewing Demonstration Center.  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 field research, including cover crop trials on corn and soybeans, nitrogen management in corn, soybean variety trial and row spacing study, ornamental corn and pumpkin variety trials, pumpkin pest management trials, and our continuous no-till area, now in its 48th year of continuous no-till production.

 

The topics to be discussed at Field Day include:

 

Managing Nitrogen for Corn

  • Emerson Nafziger, Extension Crop Specialist, University of Illinois

The Effects of Cover Crops on Water Quality & Nutrient Cycling in Southern Illinois

  • Karl Williard, Professor, Forestry, Southern Illinois University

Weather Trends & Soils

  • Duane Friend, Extension Educator, University of Illinois

Definition of Insanity & Weed Management

  • Ron Krausz, Manager, Southern Illinois University Belleville Research Center

Exploring New Clover Cover Crops for Corn

  • Nathan Johanning, Extension Educator, University of Illinois

 

The field day is free and open to anyone interested and lunch will be providedCertified Crop Advisor CEUs will also be offered.  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 Monday, July 25.  We hope to see you all there!


Storm Damage in Corn

High winds hit parts of central and north-central Illinois on June 22 and 23, flattening corn that was at stages V10 to V13 or so (4 to 7 feet tall.) Hail damaged leaf area in some places as well, but hail was not as widespread as wind damage.

Figure 1 shows corn completely flattened at our Monmouth Research & Education Center, following wind gusts up to 78 mph between 2:45 and 3:00 AM on June 22. The detailed weather record indicates that rain started to fall at about that same time, and by 6:00 AM more than 2.5 inches had fallen.

Figure 1. Corn flattened by wind in the early morning of June 22, 2016. Photo taken in mid-afternoon on June 22 at the Monmouth Research & Education Center by Angie Peltier.

Figure 1. Corn flattened by wind in the early morning of June 22, 2016. Photo taken in mid-afternoon on June 22 at the Monmouth Research & Education Center by Angie Peltier.

Even though “steamrollered” corn is a disheartening sight, several factors converged to make this much less damaging than we would often see with such events at this time of year and with corn this size. Rainfall during the first half of June has been limited in most of Illinois, and warm temperatures have meant rapid growth and water uptake. This has meant relatively dry surface soils, which has encouraged roots to grow deeper. So the crop was well-anchored by its root system when the wind blew.

As soils have dried out, water uptake has slowed slightly. The crop has been making good growth, but drying soils mean that cells in the stalk take in a little less water. This decreased the internal cell pressure, and so lowers the tendency of plants to snap off at a node – what is called greensnap. Plants of this size and at this stage, when well-watered and growing fast, are often susceptible to greensnap. Such breakage happens at upper (younger) nodes that haven’t yet been strengthened by lignin deposits. Even a slight reduction in the amount of water moving into cells is enough to reduce the potential for greensnap.

The third factor that helped the plants was the sequence of events: wind came first then rain, instead of a lot of rain followed by wind. Soil softened by rain, especially when it’s been wet and roots haven’t grown as deep, allows plants to tip over, pulling part of the root system out of the soil, and allowing plants to lie down flat on the soil. In the photo above, it’s clear that the plants, while nearly parallel to the ground, aren’t flat on the ground like they often are when corn root-lodges.

While the picture based on the event at Monmouth probably is not accurate for some places where this type of damage occurred, I think we will see this crop recover fairly quickly, perhaps with little if any effect on yield. In a study in Wisconsin, the soil was wetted and corn pushed down to the ground, causing root lodging, at different growth stages. They found less than 5% yield loss when plants were lodged at stage V10-12 and 9% loss when this was done at V12-14.

Root-lodged corn plants will gooseneck (bend towards upright) after lodging, but gradually lose their ability to do this as the stalks become lignified. If plants are only bent over with their roots intact and still in the soil, they will recover faster and better than root-lodged plants. Figure 2 shows corn in the same field as Figure 1, with the photo taken 24 hours later. In fields that didn’t root-lodge, recovery started quickly and is proceeding fast. Moist soil and warm temperatures will speed recovery. In many fields, we dodged a bullet this time.

Figure 2. Corn flattened by wind in the early morning of June 22, 2016. Photo taken about 24 hours after the photo in Figure 1, and in the same field. Photo by Angie Peltier.

Figure 2. Corn flattened by wind in the early morning of June 22, 2016. Photo taken about 24 hours after the photo in Figure 1, and in the same field. Photo by Angie Peltier.

If hail accompanied storms, as it did at Monmouth, yield loss will be related to the amount of leaf loss, or more accurately, to the decrease in the ability of the crop to intercept sunlight over the next few weeks and after pollination. Those who have hail insurance will have an adjuster evaluate leaf loss and crop stage, and yield loss will be estimated based on the loss chart. Corn is nearing the stage when leaf loss has its maximum effect on yield, but leaf area loss of only 10 or 15%, while it looks bad, will affect yield only modestly. With some new leaf area yet to emerge, and with relatively minor leaf damage in most cases reported, losses shouldn’t to large.

Wind along with hail damage may not increase the effect of leaf area loss, but the stalk will need to come back to a more upright position before light interception returns to normal, and leaf loss will extend the recovery time. Stalks of flattened plants may also have taken some direct hits by hail and show some bruising. This can interfere slightly with sugar movement through the leaf sheaths, which could cause some reduction in kernel set. Hail loss adjustment should cover this.

With some leaf area underneath flattened plants and out of reach of fungicides, and with research that shows that that hail-damaged leaves benefit no more than intact leaves from foliar fungicide, there’s little to suggest that fungicide should be applied now. Having leaves near the soil during and after heavy rain could encourage the start of foliar diseases such as gray leaf spot. Scouting for such diseases should, regardless of plant damage, be a high priority as pollination approaches in the coming weeks.


Planting Date: Corn or Soybean First?

Corn planting in Illinois has gotten into gear over the past week, with 12 percent of the state’s crop planted by April 17. That’s close to the planting pace of a year ago, and is behind the 5-year average only because that average includes 2012, when nearly half of the state’s corn crop was planted by mid-April. Illinois corn yield averaged 105 bushels per acre in 2012, while in 2014, the year with the record-high corn yield of 200 bushels, less than 5 percent of the Illinois corn crop was planted by this time in April. So while planting date is important, it is often overruled by what happens with the weather during the season.

We’ve run corn planting date studies at a number of locations over the past decade, with four planting dates at each site beginning in early April and going through late May or early June. We set the highest yield among the four planting dates at 100%, then express yields at the other three dates as a percentage of the highest yield. While percentage change is a good way to combine data over a number of sites, sites with low yields tend to inflate these percentages, and high yields mean lower percentages differences.

We have more data from central and northern Illinois than from southern Illinois, where wet conditions often rule out early planting. What we have from the southern third of the state shows a somewhat higher penalty with delays on a percentage basis, but because yields tend to be lower, not on a bushel basis. We often see oddities in the data, often the result of planting into soils that aren’t yet dry enough, form weed control issues, or from inconsistent rainfall on drought-prone soils.

Results from 35 trials in central and northern Illinois over the past nine years are summarized in Figure 1. According to this, percentage yield loss penalties with planting delays have not gone up in recent years, and may even be a little smaller than we observed previously. As predicted by the line fit to the points, the planting date producing the highest yield was April 17. But the response was very flat throughout April, within one percentage point (about 2 bushels) of the maximum between April 5 and April 25.

Figure 1. Corn planting date response over 35 Illinois site-years, 2007-2015. Yields are expressed as a percentage of the yield produced by the highest-yielding date at that site.

Figure 1. Corn planting date response over 35 Illinois site-years, 2007-2015. Yields are expressed as a percentage of the yield produced by the highest-yielding date at that site.

In four cases yields from early April planting were more than 10 percentage points below the maximum for that site. These yield losses from early planting may have been in part due to cooler temperatures after emergence that caused a physiological effect, but they also occurred in trials where the maximum yield was low, so may also have been related to below-average water supply during mid-season, with rainfall helping later plantings more than early ones. While lower yields from early April planting about one time in ten (4 trials out of 35) doesn’t represent a large potential for loss, it does reinforce the point that getting corn planted by mid-April isn’t likely to produce higher yields compared to planting in the second half of April.

From the line in Figure 1 we predict yield loss for April 30 of only 1 percentage point (2 bushels), and losses of about 4% (8 bushels), 8% (17 bushels), and 14% (29 bushels) with planting on May 10, May 20, and May 30, respectively. We don’t have a lot of data for June planting, but the yield loss going into June is at about 2 bushels per day of delay, and is accelerating.

Soybeans

We’ve been running soybean planting date studies over the past six years at the same sites as the corn planting date studies. Our earliest soybean plantings were generally in the second week of April; we did not try to plant as early in April as possible. Latest plantings were in early to mid-June.

As we found with corn, getting good data from such trials in southern Illinois is not easy; in some cases it was well into May before we could plant the first date, and loss of plantings due to wet soils and poor stands was not unusual. What data we have from southern Illinois shows that planting earlier is usually better, but it also makes clear that stand establishment is critical, and that planting conditions and rainfall after planting can often have more effect than planting date.

The soybean yield response to over 23 site-years in central and northern Illinois is shown in Figure 2. This looks much like the planting date response for corn, though we did not see any yield loss from the earliest planting like we saw with corn. This may be because we didn’t start to plant as early. I did, however, elect to leave out the 2012 data from Orr Center (Pike County), where under extremely dry conditions that were relieved by rain in August, later plantings yielded twice what the mid-April planting yielded. Leaving such data out makes the figure look better, but doing so suggests that we won’t see this happen again so don’t need the data to help predict this. We of course have no way to know if that’s true.

Figure 2. Soybean planting date response over 23 trials in central and northern Illinois, 2010-2015. Yields are expressed as a percentage of the yield of the highest-yielding date within each trial.

Figure 2. Soybean planting date response over 23 trials in central and northern Illinois, 2010-2015. Yields are expressed as a percentage of the yield of the highest-yielding date within each trial.

The prediction line in Figure 2 shows that the maximum yield was at the earliest planting, and that yield loss by the end of April was about 4 percentage points, or about 2.5 bushels; average maximum yield was 67 bushels per acre. Losses by May 10 were 7% (4 bushels); by May 20, 10% (7 bushels); by May 30, 16% (11 bushels); by June 10, 21% (14 bushels; and by June 20 yield loss totaled 29% and 19 bushels per acre. On a percentage basis these loss numbers are slightly greater than those from planting delays in corn, but some of this is due to the later first planting dates for soybean, and it’s safe to say that both crops lost yield at about the same rate as planting was delayed to late May.

Prioritizing planting: corn or soybean first?

Does the similarity in yield response to planting date mean that we should move soybeans ahead of, or at least equal to, corn in terms of planting priority once planting can begin? Probably not, at least when planting can begin by mid-April. That’s in part because corn seed emerges better under tough conditions than soybean seed, so there’s less (but not zero) chance of poor corn stands with early planting.

The most common cause of soybean stand loss is heavy rainfall after planting and before emergence. The chances of getting such rain don’t depend much on planting date, but the crop takes longer to come up if it’s planted early, and this increases the chances of getting rain before emergence. Corn is not immune from this problem, but damage to corn stands usually requires low temperature at the same time the soil is wet, so is somewhat less likely. In 2015 there were corn stand problems related to rain followed by cool temperatures in late April, which resulted in what we think was “imbibitional chilling injury” or physiological damage to the seed and seedlings caused by the intake of cold water.

A late frost would hurt both early-planted crops. We’ve had much less frost injury on soybean than on corn over the years, mostly because there aren’t many soybeans planted early enough to experience frost, but also because soybean plants are susceptible to being killed by frost for only a few days as they are emerging. Late frost is rare enough, though, that this isn’t a very important consideration.

Even if corn planting starts first, we should keep in mind that getting both crops planted as soon after mid-April as conditions permit will benefit both about equally. If the next corn field to be planted is on the wet side, in other words, it might pay to go to the (drier) soybean field to plant rather than to wait, though depending on the size and type of planter, switching between crops may not be quick or easy. Planting both crops at the same time with different planters might also be an option for some.

While getting both crops planted on time is beneficial, we shouldn’t lose sight of the fact that yield losses for delays into and even past mid-May are not so large that we need to give up hopes for a good crop if we aren’t done planting by the end of April. Statewide, the average date by which half the corn crop planted is about May 4, and for soybean it’s about May 23. These are later than we’d like mostly because soils are often wet, not because we can’t plant faster once fields are fit to plant. As much as we’d like to, it’s not clear how much we can move these dates earlier; we certainly can’t fix the weather, and we can’t (or shouldn’t) plant in mud. Regardless of planting date, we need to concentrate on making sound management decisions that allow the crop to take advantage of growing season conditions.


A New Way to Look at Soybean Management

The University of Illinois is part of a large, multi-state research project funded by the North Central Soybean Research Program (funded by state checkoff programs) to look at effects of weather, soils, and management on soybean yields.

As part of this project, we need to gather basic information on at least 500 soybeans fields around Illinois for each of the crop years 2014 through 2017. These data will go into a large database that will be used to take a look at how management affects yields in a given soil type and with a certain weather pattern. In effect, each field becomes a “test plot” and with enough “plot” numbers we will be able to see effects of things like planting date, variety maturity, and other management factors on yield.

I’m asking for help from soybean producers and those who work with producers to gather this information. For now we are focusing on getting information from fields in 2014 and 2015. Each form has room to record information on up to four different fields. There are only about 20 pieces of information requested, including field location, planting date, variety, seeding rate, etc., but nothing (like names, dates, and rates of herbicide) that requires detailed records. Most of those with typical records will be able to fill in the information for a field in less than 5 minutes.

The more fields we’re able to get information on the more useful this effort will be. Anyone who wants to contribute by filling out a form and/or by working with a few others to fill out forms is asked to send me an email (click on my name above), and I will return the form(s) either as paper copies with return envelopes or as electronic files.

We’ll be asking again after the 2016 and 2017 crop years. As the largest and best state for soybean production, we are hoping to produce the largest and best set of information of all states involved in this effort. Thanks in advance for your help.

Emerson Nafziger