Spring Nitrogen Management – Form and Timing

Most corn producers have planned their spring N program for 2015, and many have already started to implement their program. Such plans might include fall ammonia application, early spring application of ammonia or another form of N, or plans to apply all of the N at or after planting. In recent years there has been a trend towards more applications per crop, and it’s not unusual today to have N applied three or four times on the same field.

In 2014 we initiated a large study with funding (from the Illinois fertilizer checkoff program) administered by the Nutrient Research and Education Council (NREC) board. One of our goals is to compare yields from different N programs. These included fall versus spring N and early spring versus split N applications in on-farm trials, and comparison of 15 different ways to apply the same rate of N in the spring in small-plot trials at several of UI research centers.

June rainfall at the three sites where we ran these trials in 2014 ranged from 8 to 10 inches, or more than twice normal amounts. This might have meant above-normal N loss potential, though we did not have water standing on these plots. We chose to use 150 lb of N as the rate for comparison; this compares to the MRTN (N rate calculator) rate of about 160 lb for corn following soybeans in central Illinois and of about 140 lb of N in northern Illinois. Using a “medium” N rate was intended to help bring out differences in N availability to the crop.

Yields at the different sites were similar at this N rate, ranging from about 200 to 220 at Monmouth and DeKalb, and from about 215 to 240 at Urbana (Table 1). Included in these trials was a full set of N rates, ranging from 0 to 250 lb per acre using UAN injected at planting time. The maximum yield at Urbana was 238 bushels per acre, reached at 230 lb N; at Monmouth the maximum yield was 235 bushels per acre reached at 224 lb of N; and at DeKalb the yield reached a maximum of 223 bushels at 225 lb of N. The range of yields at the 150-lb N rate applied using different forms and timings included the maximum yield (from higher N rates) in the trials at Urbana and DeKalb, but not at Monmouth.

While there were considerable differences among sites in how treatments ranked in terms of yield, most of the N forms and application times we compared produced similar yields when averaged across sites (Table 1). Over the three sites, the highest-yielding treatment (urea plus Agrotain broadcast at planting) yielded statistically more than the five treatments that yielded 215 bushels per acre or less, while the second-best treatment (all of the N as UAN sidedressed at V5) yielded significantly more than only the two lowest-yielding treatments (ESN and UAN + Agrotain, both broadcast at planting).

None of the other treatments differed significantly from one another, in large part because they changed rank so much from one site to another. When this happens, it lowers the predictive ability of experiments like this, since we have no way to predict how a treatment that did well at one site but not another will perform at either site (or across sites) in 2015 or 2016, or in your field this year or in future years. This is why we do trials at different sites over several years.

The 2014 results do raise the possibility that few if any of these N form and timing treatments may, in the end, stand out as being consistently better or worse than another. This isn’t alarming, but it does provide a hint that the list of “acceptable” ways to apply N might turn out to be a little longer than we might have thought. While we need to be cautious about any predictions, this also hints that some of the treatments that we’ve considered should produce higher N use efficiency – such as sidedress or split N applications – might not always do so consistently.

The highest-yielding treatment – urea + Agrotain all broadcast at planting – has not been a common method of applying N in Illinois, and may not even be considered by some to be a sound method. That we saw it do well in 2014 in no way means that it’s the “best new” way to apply N. But with Agrotain as protection against loss of N from urea due to urease activity, with urea sometimes competitively priced as a source of N, and with the speed and ease of application, this practice could gain some traction if it continues to do well compared to other treatments. It probably makes sense to wait until we see more results before committing to it, although running some strips to compare it against another method of N application might be worthwhile.

It’s dangerous to speculate about why a treatment might have done well at one site but not another based on weather differences between the two sites. In part that’s because the weather among sites was reasonably consistent in 2014 – rainfall was normal or below normal in May and above normal in June at all three sites, July was cooler than normal, and there was little stress throughout the season. It’s also the case that the weather in 2015 will probably be different than in 2014, with some of our more imaginative speculation overturned as a result. Delaying all of the N to sidedress UAN or splitting 100 lb at planting with 50 lb at sidedress did much better at DeKalb and Monmouth than at Urbana, perhaps reflecting more loss from early-applied N at those two sites. On the other hand, dribble-applying UAN at planting worked well at DeKalb but not at Monmouth. It’s not likely that we would have been able to find such differences in either the plants or the soils back at the time of application.

The 2015 trials will include fall-applied NH3, and a fall-spring split. We also added a treatment in which we’ll apply some of the N as late as tasseling time. This is a practice that some seem convinced is on its way to becoming common, given recent observations that newer hybrids take up a greater percentage of their N after pollination than older hybrids did. It is not at all clear why, even if plants take up 40 percent of their N after pollination, soil that was fertilized with N early in the season would be unable to supply that amount. In fact, N mineralization rates in mid-season run 3-4 lb of N per acre per day in better soils, and this would be enough to provide at least 40% of total crop N requirement (of roughly 1 lb per bushel) over the six weeks following pollination, whether or not any fertilizer N were still present in the soil. We’ll see what the data tell us.

Most of us can take comfort from the fact that just about any method we choose for putting N on the corn crop is likely to work reasonably well, though no method is entirely safe from unusual weather or crop conditions. We only need to look back to 2012 to find a year when no method of applying N worked very well; when water (too much or too little) becomes the main limitation for a crop, things like N management may make little difference.

A sound N management program should, though, take costs into account – not just the costs of trips across the fields and of the fertilizer material, but also the indirect costs that include such things as the chance for yield loss or of more expensive forms or application methods we might need to use if we can’t get N on when we expected to. Most changes we are inclined to make in how we manage N today involve increasing the complexity, and this often comes at a cost in time, expense, or uncertainty. Such costs have to be covered by consistent improvement in yields.

Table 1. Yield ranks of N form and timing treatments at three Illinois sites in 2014. The N rate was 150 lb per acre for all treatments. Unless otherwise indicated, UAN was injected 2-3 inches deep between rows, and urea, SuperU, and ESN were broadcast-applied. PT = at planting time; AT = Agrotain®; dribble = surface placement between rows. There was no incorporation by tillage.


Nitrogen Management – Avoiding Ammonia Injury

A lot of anhydrous ammonia is going on this spring, and in many fields the hope is to plant as soon as practicable after NH3 application. This brings up the question about potential for NH3 damage to seeds and seedlings.

Seed and seedling damage from spring-applied NH3 is relatively rare in Illinois, but it can be quite damaging, and we want to minimize the chances of it happening. Such damage is rare is because NH3 converts readily in soil to the ammonium form (NH4+) which is held on soil exchange sites and is not damaging to plant tissue. If soils are moist at the time of application and there is normal rainfall (or at least an inch or so) from NH3 application through the time of crop emergence and establishment, chances of damage are close to zero.

A small amount of NH3 remains as free ammonia instead of converting to ammonium right away, due mostly to the large increase of pH that accompanies conversion of ammonia to ammonium. If placement is shallow or if soils dry out, some ammonia can end up in the seeding or rooting zone. If you can smell ammonia at the soil surface near the row at or after planting and soils are dry, there may be enough to cause damage. Free ammonia is very toxic to young plant tissue, and if seeds are planted into, or roots grow into, a soil zone where there is ammonia, damage can result. The most common damage is death of young roots, and this can affect yield if root systems don’t fully recover.

The best way to avoid the potential for damage is to physically separate the NH3 and the seed by placing NH3 between rows or row locations. This is possible using GPS (probably RTK) and autosteer, but it means that NH3 needs to be applied parallel (not at an angle) to the rows, and application and planting need to be precise in order to avoid placing any rows right over the ammonia band. If this can be done accurately, planting can take place right after, during, or before NH3 application.

Physically separating NH3 from the seedling zone by placing NH3 deep can help, but does not eliminate the possibility of damage. Deep placement (8 to 10 inches deep) takes more power and it can be difficult to maintain uniformity of depth across wide bars. Deep placement in the spring also means placement into wetter soil. With its very high solubility, NH3 moves less distance away from the point of release in wet soils than in drier soils. This increases the concentration of ammonia in the soil, and increases the amount that might move up if soils dry to that depth. The “path” left by a knife running in wet soil is more open for upward movement of NH3, and this can increase potential for plant damage.

If it’s not possible to apply NH3 between (the eventual) rows, then separating application from planting by time can reduce damage potential. The idea is to apply NH3 early enough so that enough rainfall will occur to keep NH3 out of the seedling zone. This means relying on weather probabilities, but not certainties; there have even been some instances of plant damage from fall-applied NH3. But the chances of such damage are low, and if this is the only option, then the longer you can wait between application and planting the better. The old rule of thumb – to wait 1 to 2 weeks between application and planting – is better than waiting 1 to 2 days, but not as good as waiting a month. So as long as we understand that waiting a week or two decreases but does not eliminate the odds of injury, it’s a guideline we can live with.


Online Survey on Soybean Farming Practices

Soybean farmers who take a ten-minute online survey will help University of Illinois crop scientists and Extension educators to better understand how decisions are made in their farms regarding soybean management and inputs and to tailor programs and projects to improve yields and profitability.

Villamil requests that soybean farmers take the survey by April 10.

The survey is a collaborative effort between the Department of Crop Sciences in the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois, U of I Extension, and the Illinois Soybean Association. The Farm Journal-AgWeb Research will be distributing an invitation to participate in the survey by email.

Questions about the survey can be sent to María Villamil at villamil@illinois.edu or Anne Silvis at asilvis@illinois.edu.


Soybean Planting Date and Varietal Maturity

Along with the continuing emphasis on getting soybean planted early – in late April to early May – comes the question of soybean maturity rating, and whether early planting benefits fuller- or shorter-season varieties the most.

Planting date

Figure 1 was updated with the 2014 data from our planting date trials in central and northern Illinois. The change compared to the response I showed a year ago is mostly from the large response to delayed planting at Urbana in 2014. Here, the April 23 planting yielded 95 bushels per acre, and yields dropped as a straight line (rather than the usual accelerating loss), losing a little more than a half bushel per day of delay, to only 66 bushels per acre planted on June 15. That dragged down the line some, with accumulated losses of about 5 and 16% by the end of April and end of May, respectively. There is a lot of spread of data at different dates, so we know that actual losses won’t hit the line on the graph most of the time.

Figure 1. Soybean planting date response over 19 central and northern Illinois site-years, 2010-2014.

Varietal maturity

Jake Vossenkemper, a PhD student working with me, has been doing research to see how planting date affects yields of soybean varieties that differ in maturity. The first question is whether varietal maturity has a consistent effect on yield by itself. Data from the central Illinois region of the UI variety trials over the past 15 years shows that this effect is not very consistent – yields of later-maturing varieties can be higher or lower than those of early-maturing ones depending on the year (Figure 2). On average, though, mid-maturity varieties tend to yield slightly more than either early or late varieties, and those within a bushel of the top-yielding maturity covered a spread of about one half of a maturity group on either side of the highest-yielding group  (Figure 2). It is also clear that yields are much more closely tied to genetic potential than they are to maturity itself, even though on average varieties with very early or very late maturity tend to yield less.

Figure 2. Soybean yield as affected by varietal maturity in UI variety trials in the central Illinois region (3 sites) over 15 years, 2000-2014. Four years were selected to show contrasting effects, and the yellow line is fit to the data over all 15 years.

Planting date and varietal maturity: do they interact?

We can see in Figure 2 that the type of growing season can have a considerable effect on how yields are affected by maturity. But how does this work when planting dates are different within a growing season? To address this question we have run a series of trials using a range of varietal maturities over a number of sites in different regions over recent years. Trends in different regions were similar, but we’ll show here the large data set (12 site-years) from central and northern Illinois and one site in Iowa. Varietal maturity ranged from about 1.9 to 3.8 with the baseline at about 2.9 in the northern sites, and from 2.5 to 4.5 with the baseline at about 3.5 in the central sites.

With early (late April to early May) planting, yields across the 12 site-years were maximized at a maturity that was about 0.4 units later than the mid-maturity baseline, and yields were within a bushel of the maximum (of about 74 bushels per acre) over maturities ranging from the baseline to about 0.8 units above the baseline, or about 0.4 units on either side of the maximum (Figure 3).  When planting was at the normal time of mid-May, the maximum yield dropped to about 66 bushels, or 7 to 8 bushels lower than the maximum with early planting, in line with the expectation based on planting date (Figure 1). At the later planting, varieties with a maturity close to the baseline maturity yielded the most, and the range of maturities that yielded within a bushel of the maximum was slightly wider than with early planting, ranging from about 0.5 units below to 0.5 units above the maximum (Figure 3).

Figure 3. Interaction between varietal maturity and planting date across 12 site-years in central and northern Illinois and central Iowa, 2012-2014. The green circles are at the highest point on each curve and the red triangles indicate the ends of the ranges over which yields are within 1 bushel/acre of the maximum.

Do we see enough here to try to tailor the maturity we use for planting at different times? Probably not in terms of changing maturity on the fly as planting time approaches – the decision on best-performing varieties has to be made before then, and if made with care should be solid enough to stand regardless of planting date. But if you have fields where early planting is often possible, you might “shade” towards a little longer maturities for those, and if there are fields that often stay wet until past mid-May, choosing from among adapted mid-season varieties makes sense. There seems to some advantage in choosing to plant fuller-season varieties earlier rather than later, though that strategy tends to work against the goal of using different maturities to spread harvest.

Emerson Nafziger and Jake Vossenkemper


Soybeans and Nitrogen Fertilizer-Again

In April 2014 I wrote on the topic on N fertilizer on soybeans, reporting that our research at the University of Illinois has rarely shown a benefit in yield to applying N fertilizer during the middle part of the season. But it seems that some people, perhaps reacting to testimonials of high yields after using N fertilizer in the high-yield conditions of 2014 remain convinced that adding N fertilizer “makes high yields higher.”

Of course, most producers who got high yields – 20 Illinois counties averaged 60 bushels per acre or more in 2014, with Piatt County reporting an average of 69.2 – did so without using N fertilizer. But the idea that soybeans can’t produce high yields and at the same time fix all of the N that they don’t get from the soil is apparently a compelling one, even though it lacks much supporting evidence.

Our Illinois results

We continued a small amount of work on N on soybeans in 2014, and Figure 1 summarizes the results of 33 comparisons we have run over the past five years. In these trials the N has been applied as urea, urea with urease inhibitor (Agrotain®), and/or polymer-coated urea (ESN) that slows release. Rates have ranged from 100 to more than 300 lb of urea (45 to 150 lb of N) per acre, and applications have been made between first flower (R1) and R4, or full pod stages. I included results from a study where N was both added to untreated plots and where N was left out of a “package” of practices considered to be helpful to high yields.

Figure 1. Soybean yield and response to fertilizer N in 33 Illinois trials, 2010-2014. Green symbols indicate that the response was statistically significant (likely due to treatment and not to chance.)

Yields ranged from 39 to 87 bushels per acre, with an average of 66. We saw significant (statistically likely to have been due to treatment, not just to chance) yield increases in two of the 33 trials, both about 6 bushels above the untreated check, and a significant decrease (of a little less than 5 bushels) in one trial. The average response to using N fertilizer over all 33 trials was a half bushel (increase) per acre. There was no tendency for the response to be higher in higher-yielding trial; the ten lowest-yielding sites showed an average response of about one bushel while the 10 highest-yielding sites showed an average response of only a quarter of a bushel.

These results show that adding N fertilizer can increase soybean yield, but that also that a consistent yield increase is not likely. Getting a yield increase high enough to pay for the practice is also unlikely. The cost of the fertilizer (100 lb of urea is about $23 at the current price of about $460 per ton) plus application means that yields need so increase by 3 to 4 bushels per acre just to break even. Ignoring statistical significance, we saw a yield increase of 3 bushels or more in five of the 33 trials and of 4 bushels or more only three times.

Getting to a real-world answer

The need to find out how often and by how much fertilizer N affects soybean yields provides a perfect opportunity for Illinois farmers and fertilizer retailers and applicators to cooperate in running on-farm strip trials. I included the how-to in an article last spring, but there weren’t many takers. We don’t have funding for this, but I would like to think that there is a group of people willing to cover the costs to make this work. I’m certainly willing to do my part, also without funding. In my vision of the future, this is how agronomic decisions will be made.

Laying out a trial like one to test N fertilizer on soybean is reasonably simple:

    • Find a uniform part of a field large enough to accommodate 12 strips wide enough to apply N fertilizer to, and large enough to get accurate harvest yields with the combine. Unless N can be dropped very precisely to strips exactly as wide as the combine will harvest, N strips will need to be wider than the combine. They should be long enough to get a good yield estimate, whether that’s with a yield monitor or a weigh wagon. Record (GPS) coordinates along with soil type, previous crop and its yield, planting date, seeding rate, variety, herbicides, application date, harvest date, and anything else that you think might have affected the crop or the response.
    • Assign treatments to strips randomly within each pair of strips. Here is how this might look:
      Strip 1 No N
      Strip 2 +N
      Strip 3 +N
      Strip 4 No N
      Strip 5 +N
      Strip 6 No N
      Strip 7 No N
      Strip 8 +N
      Strip 9 No N
      Strip 10 +N
      Strip 11 +N
      Strip 12 No N
        • Apply in-season N to the strips where it was assigned. Timing and form are not fixed, but most will want to use 45 to 90 lb of actual N (100 to 200 lb of urea, possibly including a urease inhibitor; ammonium nitrate at a similar N rate is also an option) applied between stage R2 (full flower) and R4 (full pod). Injected UAN or anhydrous ammonia can also be used if crop size and row spacing allow. If you run over plants to apply by ground, you’ll want to drive (with applicator off) down the “No N” strips as well so all strips experience the same degree of damage. With aerial application, strips will need to be wide enough so fertilizer doesn’t fall into no-N strips. Make certain, either with GPS or with flags (PVC lengths installed using a soil probe work well and are visible), that you know exactly where the N went on and where it didn’t, so you can harvest correctly.
        • Harvest and record yields for each strip. Be sure that the width harvested is the same for each strip, and trim the ends after harvest if using yield monitor data. An increasing number of acres are being harvested at an angle to row direction these days, and that won’t work for these trials unless N can be applied at the same angle.
        • I’m willing to receive data from trials like this and to send back yield averages after doing stats. If you or an adviser analyze your own, I’d much appreciate getting the data so we can look at this across all sites.

        This addresses an important question, and one that will be answered adequately only with on-farm trials like this. It’s especially easy (and without cost) for those who are already planning to apply N to a soybean field in 2015, but we hope that others want to do this as well.

        Having a crop on 10 million Illinois acres that doesn’t require N fertilizer is a great advantage under today’s pressures to have crop production remain “sustainable” and to decrease the amount of N going into the rivers. We simply cannot afford to start applying N to large acreages of soybean without knowing if it’s providing a response. We do know that, at least in some years, fertilizer N applied in July or early August won’t all be taken up by the crop, and that part of any N from fertilizer left in the soil after soybean harvest will end up in tiles lines. Can we afford that?

        I’d be glad to hear from anyone with questions about this, and from those who are interested in running a trial or two in 2015.


        Spring Cover Crop Field Day March 26th – Ewing Demonstration Center

        Join us on Thursday, March 26th, 2015 for the  Spring Cover Crop Field Day at the University of Illinois Extension Ewing Demonstration Center.  Registration will start at 8:30 a.m. and the program will begin at 9:00 a.m., rain or shine.  The Ewing Demonstration Center is 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.

        Cover crops have many benefits to the soil, environment, and overall crop production and management.  Topics covered during this field day program include:

        Challenges of Grazing Lush Spring Forage

        –          Travis Meteer, Extension Educator, U of I Extension

        Techniques for Planting into Cover Crop Residue

        –          Mike Plumer, Private Consultant

        Understanding the Soil Profile Beneath Your Feet

        –          Bryan Fitch, Resource Soil Scientist, NRCS

        Which One to Choose? Cover Crop Species Selection and Demonstration Trial Tour

        –          Nathan Johanning, Extension Educator, U of I Extension

        Some of the program highlights will be the demonstration trial planting of cover crops, including 17 different cover crops and combinations illustrating first hand the characteristics of the cover crops and what benefits they bring to your soil and crop production system.  Also, (weather and soil conditions permitting) we will have a soil pit dug, exposing the soil profile, where NRCS Resource Soil Scientist, Bryan Fitch will lead us through the characteristics of our southern Illinois soils to enhance understanding of the importance of a healthy soil.  Also Certified Crop Advisor CEU credits will be available (2.0 Soil & Water Management & 1.0 Crop Management) for the program.

        This field day will be free and open to anyone interested in learning more about cover crops.  A light lunch will be provided and this is a great way to talk to fellow growers to learn more from their challenges and successes incorporating cover crops into their cropping systems.  Please call the Franklin County Extension Office at 618-439-3178 for more information and to register by March 24th.  We hope to see you there!


        Brownstown Agronomy Research Center Cover Crop Field Day – Nov. 13

        Mult-species cover crops

        Mult-species cover crop trial - Brownstown Agronomy Research Center

         

        University of Illinois Extension and the Fayette County SWCD are hosting a Cover Crop Field Day on Thursday, November 13, 2014 from 9:00 – 11:00 a.m. The field day will be held at the U of I Brownstown Agronomy Research Center, 1588 IL 185, Brownstown, IL (Directions here).

        The field day will include tours of the current cover crop research trials being conducted at the Center. Extension educators and NRCS field staff will be on hand to discuss cover crop species selection, the effects of planting date and seeding method on cover crop establishment, factors influencing soil health, as will share their experience on the challenges and successes of cover crop establishment. 2.0 CCA-CEU credits in Soil & Water Management have been requested.

        For more information, contact:

        Robert Bellm,  U of I Extension
        618-427-3349  rcbellm@illinois.edu
        http://web.extension/illinois.edu/barc

        Tony Pals, Fayette County SWCD
        618-283-1095, ext. 3  tony.pals@il.nacdnet.net


        Ewing Demonstration Center Fall Cover Crop Field Day – Nov. 6th

        Join us on Thursday, November 6th, 2014 for the the Ewing Demonstration Center Fall Cover Crop Field Day.  Registration and refreshments will start at 8:30 a.m. and the program will start at 9:00 a.m., rain or shine.  The Ewing Demonstration Center is 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.

        Cover crops have many benefits to the soil, environment, and overall crop production and management.  Topics included in this field day program are:

        Establishment Challenges and Successes

        – Robert Bellm, Extension Educator, University of Illinois Extension

        Calibrating Success:  Drill and Planting Calibration

        – Marc Lamczyk, Program Coordinator, University of Illinois Extension

        Which One to Choose? Cover Crop Species Selection and Demonstration Trial Tour

        – Nathan Johanning, Extension Educator, University of Illinois Extension

        In addition, we also have a demonstration planting of cover crops established late this summer so you can view the growth and characteristics of the cover crops first hand and learn more what benefits they bring to your soil and crop production system.

        This field day will be free and open to anyone interested in learning more about cover crops.  Please call the Franklin County Extension Office at 618-439-3178 for more information and to register.  We hope to see you there!


        Volunteers Needed for Sampling Corn Grain

        In June with wheat harvest underway, I asked people to send in grain samples so that under an NREC-funded project we could measure P and K levels to try to sharpen up our nutrient removal numbers.

        We got a few wheat samples. We also, thanks to the Illinois Soybean Association, found a way to get a good number of soybean samples to measure P and K after they are tested for protein and oil.

        Our real need now is to get corn grain samples from the 2014 harvest. Thanks to some generous volunteers, we’ve been able to cover getting samples from most of southern Illinois and parts of the rest of the state. The biggest need we have now is for samples from Illinois north of I-80, and in central Illinois with the exception of the westernmost part of the state.

        We’re not trying to get uniform coverage across the state, but would like to find people who could gather 20 to 30 samples per county in the large corn-growing counties, with some samples from each county. Individual producers can send in samples from several different fields, but having volunteers to take samples within a county or area will be more efficient. Maybe a group of producers getting together for a meeting could each bring 3 or 4 samples.

        The process of collecting samples is as painless as we can make it:

        1. Each volunteer sends an email to NPKremoval@gmail.com giving the number of sample bags he or she would like and the shipping address to which they should be sent. The shipment of the bags will include a box (or boxes) with prepaid shipping labels so samples can be sent to us here at the University of Illinois.

        2. Each bag will have a blank label to record the field location. We prefer GPS coordinates, or ZIP code if GPS isn’t possible. The only other thing we’re asking for is yield level – just an estimate for the field. If the sample comes from a combine it can be the monitored yield level in the area of the field where the sample was collected.

        3. Each sample should be about 200 g (6 ounces) of grain, or about two handfuls.

        4. When all samples have been collected, send them in the box provided with the prepaid shipping label. Send them early in the week so they don’t sit over the weekend if there is wet grain.

        5. For those who want to see the numbers from their own samples, we’ll put a blank on the label for an email address – this will be optional.

        Please email me if you have any questions about this. And thanks for the help.


        Destructive diseases of soybean – sudden death syndrome and white mold – observed in the state

        Signs and symptoms of a few soybean diseases have begun to show up in the last few weeks in some areas of the state.  Two of these diseases, sudden death syndrome (SDS) and Sclerotinia stem rot (a.k.a. white mold) certainly are going to cause economic losses in some growers’ fields this year.

        Symptoms of SDS that currently are being observed are interveinal chlorosis and necrosis of the leaves (veins remain green while the tissues between the veins turn yellow and then brown).  These symptoms look exactly like the foliar symptoms caused by a different disease, brown stem rot.  Brown stem rot, however, will cause internal browning of the pith in soybean stems, while SDS does not affect soybean stems.  On SDS-affected plants, the leaves will fall off eventually, while the petioles will remain attached to the stems and branches.  In some cases, a bluish-white mass of spores of the SDS fungus (Fusarium virguliforme) may be observed on the roots.  Although the foliar symptoms of SDS are now being observed, infection by the SDS fungus occurred during the seedling stage, not long after planting.  The symptoms that are now being observed are the effect of toxins that the SDS pathogen produces that are phytotoxic.  Cool and wet weather after planting and the recent rainfall received in parts of the state were favorable for infection and disease development, and are the reasons why SDS incidence is high in some areas this year.  The primary method of managing SDS is to choose the most resistant soybean varieties available.  Some evidence has shown that high soybean cyst nematode (SCN) egg populations may also increase the likelihood of severe SDS; therefore, managing SCN populations through resistant varieties and crop rotation may also reduce the risk of SDS.  Unfortunately, there currently are no fungicide products registered that are effective in managing SDS, but an experimental fungicide seed treatment known as “ILeVO” that is currently making its way through the EPA registration process has shown efficacy against SDS in University of Illinois field trials.

        Symptoms of sudden death syndrome of soybean (Photo by C. Bradley).

         

        A bluish-white mass of spores of the SDS fungus (Fusarium virguliforme) on a soybean root (Photo by C. Bradley).

         

        White mold can be observed in fields located in the northern half of Illinois this year.  The appearance of this disease also is weather-related.  Areas in the northern half of the state, that were cooler and wetter than normal after soybean plants began to flower, are the areas that are affected the most severely.  Unfortunately, once white mold signs and symptoms are detected in the field, fungicide applications generally will be futile, as the damage has already been done.  Management of white mold was discussed in an earlier article of the Bulletin this year (http://bulletin.ipm.illinois.edu/?p=2412).  Growers with severe levels of white mold may encounter some discounts at the elevator this year for high levels of foreign matter.  Some sclerotia (dark survival structures produced by the white mold fungus – Sclerotinia sclerotiorum) that are formed on plants may similar in size to the seed, and will make their way to the hopper and eventually the elevator, where discounts may be received.

         

        Soybean plants dying prematurely because of white mold in a field in Champaign County (Photo by K. Ames).

         

        White mycelia of the white mold fungus (Sclerotinia sclerotiorum) on a soybean plant (Photo by C. Bradley).