Soil Nitrogen and N Management Following the 2016 Crop

The 2016 growing season has been a very good one for corn in Illinois, with the November yield estimate of 202 bushels per acre, slightly higher than our previous best of 200 bushels per acre in 2014.

In sharp contrast to the wet June of 2015, most of Illinois received below-normal rainfall in June 2016, with parts of western and southwestern Illinois receiving less than an inch for the month. With May rainfall close to normal across the state in 2016, the wet soils and N loss conditions that we saw over most of Illinois in 2015 never materialized in 2016.

2016 soil nitrogen and N response

In our N-tracking project funded by the fertilizer assessment (Nutrient Research & Education Council), we apply 200 lb. of nitrogen per acre as fall-applied ammonia, early spring-applied ammonia, fall ammonia plus spring-split UAN, or spring-split UAN. We then sample during the spring to see how much N remains in the top 2 feet of soil.

Averaged over three locations in 2015, sampling in mid-June and at tasseling recovered about 70 and 42 percent, respectively, of the amount of N applied as fertilizer. In 2016, we found a little more N than this –about 76 percent in mid-June and 47 percent at tasseling. Grain yield levels didn’t differ greatly between the two years, but more of the N needed by the crop was taken up by tasseling in 2016 compared to 2015. Yields were similar in both years, though, so having more N taken up by tasseling did not clearly lead to higher yields.

Warm soils and wet weather in December 2015 caused a lot of concern about loss of fall-applied N in 2016. We did not, however, find lower amounts of soil N following fall N applications than we found following spring applications in 2016. But there were some differences between the two years in how much of the N recovered was in the ammonium form (coming directly from ammonia application) and how much was nitrate. Nitrate can move in the soil and be lost.

In both 2015 and 2016, about 80 percent of the N recovered in early May following fall ammonia application was nitrate. Following spring ammonia application, 59 percent of the nitrogen was nitrate in early May in 2015, while in 2016 only 39 percent was nitrate. By early June, when N uptake by plants began, 80 to 90 percent of the recovered N was nitrate in both years, regardless of timing of application.

It’s clear from these numbers that applying ammonia in the fall versus spring did not have much effect on how well the nitrogen was protected by remaining in the ammonium form, at least by the time N uptake began. This suggests that N loss is tied more closely to conditions during N uptake (June) than to N fertilizer timing, although sidedressing ammonia, which we did not do in this study, would have increased the amount present as ammonium.

Most N rate trials are showing considerably less N needed in 2016 compared to 2015. This year, we’re often seeing yields leveling off at N rates of only 140 to 160 lb. N per acre, at yield levels between 200 and 250 bushels per acre. We think that this reflects both the large supply of N from mineralization of soil organic matter under the favorable conditions of May and June this year, and also the drier June weather this year that limited N loss and root damage. Another sign of a good supply of N from the soil was the delay in development of N deficiency symptoms in corn grown without fertilizer N. It was common in 2016 to see unfertilized corn in our trials remain dark green into mid-June, when the crop was 3 feet tall or taller.

Nitrogen in the soil this fall

One might expect that less N loss might lead to higher amounts of N left over at the end of the season. We aren’t seeing this in most cases. Dan Schaefer of IFCA took soil samples at the time of crop maturity at a number of on-farm sites, nearly all of these showed soil N levels of less than 6 or 7 ppm, which we consider to be baseline levels. We’re also finding low soil N levels in samples taken following harvest in our N-tracking trials. The only place we’re seeing elevated levels is at N rates considerably higher than those needed to maximize yield. Using too much N is never a good idea, and that was especially true in 2016.

Those who added N late in late vegetative stages this year in addition to normal rates applied earlier might well have ended up with more soil N than usual after harvest. A vigorous cover crop like cereal rye will take some of this up. But the low levels of soil N in fields with normal rates of fertilizer N may not have enough N to produce vigorous cover crop growth. Trying to “prime” cover crop growth by applying fertilizer N this fall will increase N uptake, but may not necessarily increase net uptake after subtracting the amount applied.

Despite slow cooling at the start of November this year, soil temperatures are now below 50 degrees over most of northern and central Illinois, and ammonia application is underway. Soils are mostly in good shape for this, but application should be delayed in fields with wet surface soils .

Nitrogen management for the 2017 crop

We can think of no good reason to adjust N rates, unless planned rates are substantially higher that the 175 (155 in northern Illinois) and 210 lb. N per acre or so calculated by the N rate calculator for corn following soybeans and corn following corn, respectively, in the region of Illinois where fall N is used. If planned rates are higher than this, a downward adjustment is in order. We never know what the spring will bring, but it makes more sense to react to loss conditions if they occur that to apply more N “just on case.”

If the plan is to apply some N in the spring after fall application, consider subtracting that amount from the fall application rate in order not to exceed the suggested rate. If 2017 is like 2016 with regard to N nutrition, using more than suggested rates will nothing to increase yields, but will increase both economic and environmental costs.

There’s been a lot of talk in recent years about how CEC “limits” the amount of N that should be applied to a given soil; the maximum amount commonly mentioned is 10 lb. N per unit of CEC. CEC is a measure of the concentration of negatively-charged exchange sites in a soil. Soils with more clay and more organic matter have higher CECs; silt loam or silty clay loam soils with 3 or so percent organic matter typically have CEC values between 20 and 40. That’s more than enough to “hold” the right amount of N.

There’s no sound basis for considering CEC a measure of “N-holding capacity,” any more than to consider it as potash- or calcium-holding capacity. One unit of CEC in the topsoil will hold 360 lb. of ammonium, so a soil with a CEC of 20 would have only 2.5% of its exchange sites occupied by ammonium if it were all on the exchange sites. Ammonia applied to soil dissolves instantly in soil water, then converts quickly to ammonium. Like any positively-charged ion (cation) in the soil solution, some ammonium ions quickly occupy exchange sites, and some stays in soil solution. Little if any ammonium does not move down in most soils, regardless of the amount applied (within reason.) A possible exception is light, sandy soils with very low CEC values. Nitrogen should not be applied in the fall in such soils.

So there’s no reason to be concerned about CEC values when it comes to applying N on the vast majority of Illinois soils. Instead, base N rates on the N rate calculator, which is based on research showing what rate can be expected to maximize profit. And then apply N responsibly in order to minimize N loss and to keep N for the crop.

Diplodia ear mold at harvest: What can be done now?

Producers in western and west-southwestern Illinois may have observed symptoms of Diplodia ear mold during harvest.

Figure. Healthy corn kernels (left) and kernels showing symptoms and signs of Diplodia ear mold have been found throughout the western and southwestern Illinois crop reporting districts and in corn harvested at the Northwestern Illinois Agricultural Research and Demonstration Center in Monmouth.

Figure. Healthy corn kernels (left) and kernels showing symptoms and signs of Diplodia ear mold have been found throughout the western and southwestern Illinois crop reporting districts and in corn harvested at the Northwestern Illinois Agricultural Research and Demonstration Center in Monmouth.


Diplodia Symptoms and Machinery Adjustments at Harvest. Diplodia ear mold can cause lightweight kernels with a dull grey to brownish color and sometimes small black structures call pycnidia (Figure). The infected kernels are prone to breakage and can result in poor test weights, poor grain quality and fine materials in the hopper or grain bin. Adjusting combine settings can help to maximize grain cleaning and minimize breakage.

Figure. Kernels on ears that have symptoms of Diplodia ear mold may appear dull and more greyish than healthy kernels. Breaking an ear in half may reveal small black fruiting structures call pycnidia that are produced by the fungus that causes Diplodia ear mold.

Figure. Kernels on ears that have symptoms of Diplodia ear mold may appear dull and more greyish than healthy kernels. Breaking an ear in half may reveal small black fruiting structures call pycnidia that are produced by the fungus that causes Diplodia ear mold.


How Much is Out There? An informal survey of several grain elevators and farmers in Western Illinois had reports of less than 2 to more than 50% kernel damage from Henry to Madison County, respectively. Factors such as planting date, the timing of rain events after fertilization and hybrid susceptibility can result in a range of damage within the larger region and even within a farming operation.

Dockage at the Elevator. Further conversations with elevator and ethanol facility personnel suggested that the threshold for accepting damaged grain can vary depending upon the local market and end-use. The price at which a farmer can market grain begins to decrease for every percentage point of damaged kernels above 5% and some grain elevators will set a damage threshold above which they will not accept the grain depending upon the end use and how quickly the grain will leave the elevator.

It is important for those producers that encounter Diplodia ear mold to be in communication with their crop insurance agent. While the high yields expected this year may offset lower grain prices overall, those farmers with low sale prices due to a lot of dockage may be able to recoup some of their losses.

Stenocarpella maydis, the fungus that causes Diplodia ear mold, metabolizes the starches in corn kernels leaving them lighter weight than non-infected kernels. The ethanol manufacturing process uses bacteria to turn corn starch into simple sugars, eventually fermenting them to yield ethanol. Diplodia-damaged kernels can yield less ethanol and may be why elevators that supply ethanol plants may have a lower threshold (one mentioned 10%) for damaged kernels than others.

One positive is that unlike Aspergillus, Fusarium or Gibberella ear molds, Diplodia ear mold is not associated with a mycotoxin. However, regardless of whether infected kernels are in the field, in the combine hopper, semi trailed or grain bin, unless the grain is cooled and dried to below 15% moisture, the fungus will continue to grow and metabolize starches, lowering test weights and grain quality. Additionally, unless properly dried, the fungus can colonize uninfected kernels that are damaged during harvest or storage operations.

Drying and Storing Moldy Grain. With on-farm storage, many crop producers have the option to hold onto their grain to market it at a later time. Storing diseased grain separately and for only short periods of time is recommended to reduce the chance of additional losses.

Agricultural engineers from Iowa State University have produced several tools that can help those interested in learning more about just how long air drying may take with a given fan and grain bin size and the crop moisture and air temperatures outside. For those that have the ability to add heat to the drying process, these experts have also produced tools that can help in factoring all of the costs associated with drying with or without heat.

Here are resources related to these topics produced by Iowa State University Agricultural Economists and Engineers:

Grain Storage – Quality Management​:
Fan Performance

Grain Storage – Economics:
Grain Drying Economics
Grain Storage Economics

General information about Diplodia ear mold and practices to help reduce disease risk in future corn crops can be found here.

Corn Earworm, European Corn Borer, Fall Armyworm, or Western Bean Cutworm: Which One Is Causing the Injury I’m Finding on My Corn Ears?

Several questions about injury on corn ears has made it way to my desk the past week.

Insect injury to corn ear (photo courtesy of Duane Frederking).

Damaged ear tips, missing kernels, and fungal pathogens are all being reported. Several insect pests in Illinois could be the culprit. Corn earworm, fall armyworm, European corn borer, and western bean cutworm are pests of Illinois cornfields. Their larvae all feed on the ears of corn plants.

So how does one determine the cause of ear damage this late in the season? The answer is simple: You really can’t. At this time in the season, it is rare to find any larvae still feeding on corn ears. Without larvae, you can’t be positive if injury was caused by earworms, corn borers, fall armyworms, or bean cutworms, as they cause very similar injury. Let’s look at each insect individually.

Corn earworm. Two generations of corn earworm infest Illinois cornfields each year. Because earworms generally do not overwinter in Illinois, summer populations arise primarily from immigration of moths from southern states in late spring and early summer. Infestations of earworm larvae can cause injury to corn plants, including slight defoliation of leaves, damage to the tassel, and consumption of silks and kernels. The second corn earworm generation usually occurs during pollination. Larvae enter the ear primarily through the silk channel, unlike European corn borer and fall armyworm, which enter through the husks or cob. As silks dry, corn earworm begin feeding on kernels. Larvae feed at the tip and along the sides of the ear near the tip, continuing to feed until they mature. At that time the larvae drop to the ground to pupate. When leaving the ear, corn earworm may drop from the ear tip or create exit holes by chewing through the husk. These exit holes can be mistaken for entrance holes caused by other larvae.

Corn earworm larvae.

Corn earworm injury to corn ear.

European corn borer. Two to three generations of European corn borer occur in Illinois each year. Injury to corn ears is caused by the second and third generations. Loss of grain to larvae’s direct feeding on kernels has not recently been an issue in field corn, but in sweet corn and seed corn, losses can be significant. We’ve also received reports of corn borer feeding in non-GMO corn. Larvae feed on pollen and silks before entering the ear. Entry to the ear is also gained by tunneling through the shank and cob. Ear feeding by corn borer larvae is not focused on any one area. Injury can be found at both ends and along all sides of the ear. Larvae feed until mature; they overwinter as fifth-larval instars in stalks and plant debris.

European corn borer larva (photo courtesy of Marlin Rice, Iowa State University).

European corn borer injury to corn ear (photo courtesy of Marlin Rice, Iowa State University).

Fall armyworm. Like the corn earworm, fall armyworm moths migrate north into Illinois each year. Fall armyworms are a concern for cornfields from mid- to late summer. They cause serious leaf-feeding damage and feed directly on corn ears. Late-planted or later-maturing hybrids are more susceptible to fall armyworm injury. Most common is pretasseled corn. Larvae consume large amounts of leaf tissue, but as corn plants develop, larvae move to the ear. Unlike the corn earworm, the fall armyworm feeds by burrowing through the husk on the side of the ear. Larvae also enter at the base of the ear, feeding along the sides and even tunneling into the cob. They usually emerge at the base of the ear, leaving round holes in the husks.

Fall armyworm larva.

Fall armyworm injury to ear.

Western bean cutworm. A mid- to late-summer pest of corn, western bean cutworm moths begin to emerge in early July. Though some leaf feeding occurs, larvae feed primarily on silks, tassels, and developing kernels. Larvae of the western bean cutworm are not cannibalistic, and several larvae may infest one ear. Entry to ears is gained through silk channels or by chewing through husks, injuring the tip, base, and sides of the ear. Larvae feed on kernels until about mid-September, when they exit through husks. Reports of western bean cutworm injury have been very sporadic the past couple of years.

Western bean cutworm (photo courtesy of Marlin Rice, Iowa State University).

Western bean cutworm injury to corn ear (photo courtesy of Marlin Rice, Iowa State University).

Any one or combination of the aforementioned insects could be the cause of the injury being seen in cornfields. As much as we would like to be able to pinpoint the direct cause of injury, that is often impossible this late in the season. Summer scouting is the key to determining the potential insect culprits.


(Updated from 2005 article)

How can we improve your experience with the Pest Degree Day Calculator?

Insects require a certain amount of heat to develop from one stage in their life cycle to another (eggs to larvae to pupae to adults). Degree-days measure insect growth and development in response to daily temperatures. The accumulation of these degree-days can be measured over a period of time and used to estimate growth and predict insect development. Calculating degree-days allows us to predict when significant biological events such as the appearance of insect pests may occur or when they may reach a life stage that is damaging to a particular crop.

Fortunately, we have at our fingertips a calculator that can help us calculate degree-days for selected pests. The Pest Degree Day Calculator is a result of a collaborative scientific effort that combines daily weather data collected by the Water and Atmospheric Resources Monitoring (WARM) Program (Illinois State Water Survey, Prairie Research Institute, University of Illinois) and the Integrated Pest Management (IPM) Program (Department of Crop Sciences, University of Illinois) to provide daily, up-to-date information about pest and crop development in Illinois. Many of you may utilize the calculator to predict cutting dates in your area for black cutworm or to identify when rootworm hatch may be occurring.

We are working hard to improve our Degree Day Calculator. Let us know what you like, don’t like, or what you would like to see changed. Take our survey to share your thoughts: Thanks in advance for your help!

Agronomy Day 2016

Agronomy Day is a collaborative field day hosted by the Department of Crop Sciences in partnership with several academic units in the College of Agricultural, Consumer and Environmental Sciences (ACES). From nitrogen management to drone demonstrations Agronomy Day shares cutting-edge research with practical implications for your farm or business. CEU and CCA credits are available during tour stops. Want to know more about Agronomy Day? Sign up now for the Agronomy Day mailing list!

For directions and a list of field tour presentations, please visit the Agronomy Day web site.

Soybean: crunch time to come

The 2016 Illinois soybean story is similar to the corn story; current (July 24) crop ratings for both crops are similar to those we saw in 2014, when we produced the highest-ever yields for both crops. Illinois producers matched the 2014 soybean yield (56 bushels per acre) in 2015, despite the crop’s getting off to a very rocky start last year. Few surprises in crop production have been greater than that of seeing fields that looked marginal in July 2015 go on to produce 60, 70, or even 80 bushels per acre.

Compared to the 2015 soybean crop, the 2016 crop took off well and has looked good the whole season in most Illinois fields. Stands are good, growth is generally uniform, and unlike most seasons, there are few drowned-out spots in many areas if the state. In some places where June was dry then heavy rains came in July, Phytophthora has developed. But overall, the 2016 soybean crop is the most visually appealing one we’ve seen in a long time.

While we appreciate the outstanding appearance of this year’s soybean crop, we saw last year that soybean appearance even in late July is a poor predictor of yield. In fact, it’s possible that the soybean crop might even look (and be) “too good” for this time of year. We don’t say that about the corn crop, so why is soybean different?

Corn is a highly efficient crop that makes enough leaf area to form a complete canopy but not much more than that. Corn also has a single ear attached to the stalk, and all leaves feed sugars into that same stalk, so every leaf contributes to both forming and filling the ear. Pollination takes place over the course of a few days, and high yields depend on the number of kernels, so it’s “all hands on deck” for corn leaves, and having too much canopy or plants too tall is not an issue.

Soybeans differ in that flowering takes place over a period of several weeks, and the success of flowering (that is, number of seeds/pods formed) is closely tied to the ability of the leaf at each flowering node to photosynthesize at a rapid rate while the flowers are forming. When leaves are large and plants are tall, not all leaves can compete successfully for light, and they can be partially shaded at critical times, resulting in fewer pods formed and less ability to fill the pods that form.

Petioles (stems that support leaflets) in soybean can be as long as 18 inches to help leaves get up into sunlight. But when stems get to be more than 40 inches tall (to the tip of the stem, not the top of the canopy), lower leaves will be shaded or partly shaded much of the time.

Shading of leaves attached to the lower stem nodes is a problem not only in terms of pod numbers that form at those nodes, but also in these leaves’ getting enough sunlight later in the season to fill those pods. Tall plants with a lot of leaf area in mid- to late August may have few pods forming on the lower stem, and while this might be partly offset by having more pods at mid- to upper nodes, total pod numbers per plant is often decreased.

This “overgrowth” phenomenon in soybean has been known for a long time, and has given rise to various attempts aimed at reducing plant height or leaf area to “help” the soybean plant get over this problem. Dinging leaves with herbicide or growth regulator, “topping” plants by hand or mechanically, and generally undoing what (large) plants spent time and effort building has been the common theme. I’ve seen this work in the subtropics where intact soybean plants turn into vines, but in the Corn Belt, such treatments have almost always done more harm than good. It’s just difficult to get consistently positive results by beating up soybean plants.

By this time of the season soybean plants have not yet reached their maximum height; that will happen by about the second week of August, and plants could add 25 or 30% more to their height by then. Warm temperatures and good soil moisture will keep them growing. There’s not a lot we can do about that.

There is one thing we might not do that will provide some help: application of in-season nitrogen. Application of N (and fungicides) tends to keep leaves a little greener and to increase growth rates a little. Neither of these would be a good thing for a soybean crop that is already approaching stem height of 30 to 36 inches. For those who might want photos showing how tall your soybean crop is, have the person standing in them bend his or her knees a little. Or just acknowledge that really tall soybean plants are not usually the highest-yielding and that they are no indicator of best management.

Heavy canopies tend to keep humidity higher in the canopy, which can lead to more disease development. I haven’t heard too much about white mold so far, but these are the type of conditions that favor its development if it has already infected flowers. There are some other foliar fungal diseases such as frogeye leafspot that may be favored if it stays damp.

While we’ve found a yield increase of 2 bushels per acre or more from applying foliar fungicide in about half of the trials we’ve done, we’re not able to find many clues about when it might work and when it might not. There is no correlation between response and yield level, so “making high yields higher” doesn’t work as a principle. While we can’t rule out a physiological effect, it makes sense that using fungicides to help control fungal diseases should provide the most consistent return.

What’s our best-case for the 2016 soybean crop? Some cooler, drier weather will help slow growth down a little, but that may not be enough to bring back really high yield potential. Although we are concerned about heavy canopies, we have had years when this seemed to have less effect; only by looking at pod numbers per node in mid-August will we really know. If many nodes have 4 or 5 pods like we saw in 2015, we can consider this a false alarm, or at least a case where possible negatives were canceled by some positives, even if we don’t understand how.

Is the 2016 corn crop as good as it looks?

With the exception of a few cool and wet periods in May and some areas of southeastern Illinois that stayed wet and were planted late, the 2016 growing season has been very good so far. The Illinois corn crop was planted a little earlier than normal, stands are excellent, and the crop has had outstanding leaf color throughout the spring and into mid-summer. On July 24, 82% of the crop was rated good or excellent. That matches the late July rating in 2014, the best-ever Illinois corn crop at 200 bushel per acre.

Virtually all of the corn crop has completed pollination, and the half that pollinated by July 10 is now into the “roasting ear” stage (R3), with some already in the dough (R4) stage. With good soil moisture in most fields, kernel numbers are not likely to decrease due to kernel abortion, so the number of kernels in a field now is likely to be close to the final number.

As is always the case, yields are going to depend on two things: kernel counts and canopy. Counting kernels may not be great fun on a warm day, but it’s a straightforward exercise. Simply get a good count of the number of ears per acre (most people do this in 1/1000th of an acre, which in 30-inch rows is 17 ft. 5 in. of row) and then count the number of rows of kernels and the number of kernels in an average row to give kernel number per ear for several ears. Making these counts a few times across a field, and going to those spots randomly will give more realistic estimates. If the goal is to brag, choose the best spots to count. But decency requires that you move into at least the fourth row in from the outside of the field; outside rows have “indeterminable” row spacing so can’t be used to calculate yield.

Once you have the number of ears in 1/1000th of an acre and the kernel number per ear averaged over at least three ears, simply multiply those two numbers to give the number of kernels per 1/1000th of an acre. Typical numbers in a good crop might be 34 ears x 500 kernels per ear, or 17,000 kernels (17 million kernels per acre.) The tricky part of the yield estimate is trying to guess how large the kernels will get. The default we usually use at this point in the season is 80,000 kernels per bushel. We drop the 000s since kernel count is for 1/1000th of an acre, and divide kernel number by kernels per bushel. In our example, that would be 17,000 divided by 80 = 212.5 bushels per acre.

To fill kernels to their maximum will require a full crop canopy that stays green and active up until close to maturity. With warm temperatures continuing, the early-planted crop is on track to mature (reach kernel black layer) by late August or early September. So we need the canopy to maintain its color and activity (the two are very nearly the same thing) for 4 to 5 weeks more.

Leaves that turn from dark green to yellow have lost most of their photosynthetic capacity, so any lightening of canopy color is a concern. You can see canopy color loss by using a drone or otherwise getting above the crop, but a better way is to walk into the field around mid-day to see if the amount of light passing through the leaves – that is, how well-lighted the ground seems to be – has increased from what it was a week or two earlier. Reading a newspaper placed on the ground should require some squinting if the canopy is good; if it’s easy to read, too much light is getting through to the ground. Dark at ground level means the crop is intercepting 97 or 98 percent of the sunlight. We expect yield to drop by as much as 2 percent for each additional percent of light that gets through the canopy.

A number of things can cause loss of canopy light interception. One that many people worry about is having the crop “run out of nitrogen” during grainfill. The good news is that a corn crop growing on average or above-average Illinois soils, and that had enough N to stay green up to pollination, is virtually guaranteed not to run out of N during grainfill. That includes nearly all corn fields in Illinois in 2016.

Canopy color has been outstanding in most fields this year due to good mineralization, adequate (to more than adequate) N fertilizer used, and little potential for N loss in the spring. Crop N needs drop quickly once the crop is past pollination, and by now the crop in most fields is taking up no more than a pound of N per acre per day. Mineralization rates typically exceed that amount at this time of the season, so the crop needs little or no additional N from fertilizer from here on out. Much of the N applied late in fields with dark green plants was unnecessary, and we can expect some of it to exit the field through tile lines.

The main cause of loss of canopy during grainfill is having the soil get dry enough to restrict water availability to the plants. Illinois is generally well-supplied with soil water now, but with uneven distribution there are likely some areas where the water supply may be dwindling to the point that canopy function is starting to slow. Plants during grainfill may not show the distinct leaf rolling that we see with water stress before pollination. Instead, leaves exposed to the sun at the top of the plant may start to lose their green color, and this loss may continue until it rains or until leaves start to dry up.

As plants start to lose photosynthetic capacity as soils dry, they often show characteristic “firing” as leaves, starting with those closest to the ground and moving up, begin to transport their N to the upper leaves and into the ear. This is a defensive mechanism that results in some seed production as photosynthetic activity declines or stops. Because N loss from leaves means development of N deficiency symptoms, there’s a tendency to believe that having more N in the soil would have prevented firing. That’s simply not true: leaf firing results from having too little water available, and has nothing to do with the amount of N in the soil. In fact, high fertilizer N rates can increase plant and canopy size, and larger plants use water more quickly, which can trigger earlier and more severe firing.

Foliar diseases can also take a toll on the crop canopy, decreasing both yield and stalk integrity, with greater potential for stalk rot to occur later in the season. Foliar diseases seem to be fairly low this year, but scout to make sure, and consider fungicide use if diseases begin to move up the plant in the next week or so. The amount of benefit from using fungicides decreases as grainfill proceeds, and once the kernels are into the dough stage the cost may exceed the benefit.

Anthracnose leaf blight is a fungal disease that can appear during grainfill on susceptible hybrids, and when it appears in August, control by foliar fungicides may not be very good. Goss’s wilt, which can also destroy leaf area, is a bacterial disease against which fungicide has no activity. If crop canopy is physically removed by hail, no repair is possible. Insects very rarely cause extensive defoliation in a corn crop during grainfill, but scouting will help you know if there’s a problem developing.

If we continue to get enough rain and the canopy stays healthy, will the crop be as good as it looks? Yes. I’ve heard reports of kernels counts of above 20 million per acre, which would be 250 bushels at 80,000 kernels per bushel. If conditions deteriorate and the canopy declines before maturity, kernels may end up lighter and yields lower. But if conditions through August remain favorable and the canopy stays intact, kernels can get larger than this and yields higher.

What could go wrong with this year’s crop? Wind and hail always come to mind, but the frequency of these events decreases later in the season, and the fact that these have not been widespread up to now is a plus. A sudden onset of high temperatures without rainfall would limit yields in a lot of fields, but better soils in many areas have enough water today to keep the plants going for several more weeks, as daily water use rates are starting to decline. So this would be less devastating than we might expect. Late-developing foliar diseases could end grainfill early, but their larger effect, like that of late-season drought, would be to result in depletion of stalk reserves as ears take in sugars faster than the plant is producing them. This may not greatly diminish grain yields, but depleted stalks are more susceptible to stalk rots, and affected fields could lodge earlier.

With the finish line moving into sight, it’s clear that the crop has an unusually good chance to yield above trendline this year. But as in most things, there’s no guarantee.

2016 Orr Center Field Day Set For July 20

The 2016 Orr Center field day will be held on Wednesday, July 20, beginning with sign-in and refreshments at 8:00 AM. The format will be new this year, with three UI Extension specialists making presentations in indoor classrooms:

  • Weed scientist Aaron Hager will talk about weed management
  • Agronomist Emerson Nafziger will discuss crop conditions and nitrogen management
  • Ag economist Gary Schnitkey will discuss crop income projections

Indoor sessions will be followed by a short wagon tour to look at crop conditions and some of the research trials underway at the Center. The tour should be finished by 11:00 AM. Continuing education units will be available for Certified Crop Advisors.

For more information, please contact Mike Vose at 217-236-4911 or at

The Orr Center is on State Hwy 104 approximately 4 miles west of the junction of IL Routes 107 and 104 north of Perry, Illinois.

How might soybean yield be affected by hail damage?

In the early morning hours on Wednesday, June 22 a severe storm moved through western Illinois affecting crops throughout much of Henderson, Warren and Mercer Counties, including those at the University of Illinois’ Northwestern Illinois Agricultural Research and Demonstration Center in Monmouth.  Preliminary data collected by instruments maintained by the Illinois Climate Network at the center had the wind gusting to 78.1 mph and more than 1 inch of rain falling in a 10 minute period contributing to the nightly total of 3.34 inches. The National Weather Service models showed that ¾ inch diameter hail fell over the area as well. Corn plants were blown over and both corn and soybean plants were damaged by hail.

Soybeans in a planting date trial were at different stages of growth and development when the hail damage occurred; soybeans planted on April 18, May 7, May 19, and June 7 are at R2 (flowers at the upper nodes), V6, V5-6, and V1, respectively.

While plant damage occurred regardless of growth stage, the damage appeared to be most severe on the latest-planted soybeans, with stems of some plants broken over and many of the primary growing points severely damaged (Photos).

Picture1While hail damage on soybean can be shocking, the growth habit of soybean and the timing of the recent damage provide encouragement that plants will recover well. Soybeans we grow have an indeterminate growth habit, meaning that they continue to add new leaves for some weeks after flowers have begun to appear. Even early-plated soybeans have only 15 or 20% of their final leaf area now, so most leaf area is still to come. Damage to existing leaf area is thus a relatively minor problem, providing that plants remain alive and capable of forming leaves and pods. Those leaves that remain will contribute to the growth of new leaves. Leaf loss does set back plant development, similar to having planted at a later date, but the soybean canopy typically doesn’t finish developing for another 6 weeks. New leaf area should be starting to appear soon, and a few weeks from now it may be difficult to see any lingering effects of leaf loss.

A full canopy is required for a soybean crop to fully intercept sunlight to produce sugars, fill pods and maximize yield. Those fields in which hail damage lowers stand to fewer than 100,000 plants per acre or so may not be able to develop a full canopy to intercept all of the sunlight that they need to produce higher yields. Provided that the primary growing point of most plants remains unaffected, populations are unlikely to suffer. Most plants that had experienced hail are damaged but not killed, but after flowering, plants with most of their leaf area missing may not recover fully. Fortunately, a full stand of healthy soybean plants can produce more leaf area than they might need for full yields, so some leaf loss now should have minimal effect on yield potential.

It’s been warm enough that flowering in early-planted soybeans began before the longest day of the year this year. While yield loss due to hail damage starts to accelerate as plants pass flowering and enter podsetting stages, we do not believe there is much irretrievable yield loss yet, as long as plants are able to get enough water and the canopy stays healthy.

-Angie Peltier and Emerson Nafziger

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.