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 mvose@illinois.edu

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.


Does the Corn Crop Need More Nitrogen?

Except for some areas of southeastern Illinois, the 2016 corn crop went in well, and on June 12 was rated at 75% good or excellent. Warm temperatures have speeded up growth, and although below-normal rainfall, especially in western Illinois, is starting to cause some concern, the 2016 corn crop is off to a very good start.

The corn crop this year has excellent stands and there are few drowned-out areas, though there is some unevenness depending on when the crop was planted and how much rain it received after planting. The most noteworthy feature, though, is the dark green color of the crop, especially the crop that was planted in mid-April. This is among the greenest corn crops I have seen in Illinois.

Not only is the crop green where N fertilizer has been applied, it is also green where no N fertilizer was applied. In a June 9 photo taken in one of our N trials, the zero-N treatment shows slightly less growth than the treatment with 200 lb. N applied on April 18 as NH3, but leaf color is about the same without N as with a full N rate (Figure 1). We don’t expect this to last as N uptake kicks into high gear, but the crop has taken up a fair amount of N that didn’t come from fertilizer.

Figure 1. Photo taken on June 9 of V7 corn in a research trial near Urbana, Illinois. The crop followed soybean, and was planted on April 18.

Figure 1. Photo taken on June 9 of V7 corn in a research trial near Urbana, Illinois. The crop followed soybean, and was planted on April 18.

Soil N changes

Soils in the plots shown in Figure 1 have been sampled several times this spring to monitor changes in N. In samples taken on June 3, plots without fertilizer had 49 lb. per acre of plant-available N (PAN, nitrate-N plus ammonium-N in the top 2 feet of soil) and those with 200 lb. of N applied as early spring NH3 had 222 lb. of PAN. Unfertilized plots had about 40 lb. less soil N on June 3 than they had two weeks earlier, but most soil N numbers remained relatively constant during May. Fall-applied N has been present mostly as nitrate this spring, and, and spring-applied NH3 has moved steadily towards nitrate, going from 25% nitrate (75% of the N recovered as ammonium) after application on April 18 to 71% nitrate on June 3. Unless soils get wet soon and stay wet for some time, nitrate will stay in the soil and remain available for uptake.

We saw somewhat inconsistent changes in soil N at some of the other research centers where we’re tracking N this spring. At DeKalb, where 4 inches of rain fell on May 11, soil N following 200 lb. N applied as NH3 in April fell from 375 lb. on May 7 to 176 lb. on June 3, while the unfertilized check rose from 80 to 90 lb. of soil N per acre. At Monmouth, the unfertilized checks had 167 lb. of soil N on June 7, and plots with 200 lb. N as fall-applied NH3 had 288 lb. of N in the soil while those with 200 lb. N as spring-applied NH3 had 260 lb. of soil N.

Fields that Dan Schaefer of IFCA is sampling under the N-Watch program are showing little spring loss of soil N, and some increases. Nine sites in Sangamon County that received 225 lb. of N last fall and winter had an average of 363 lb. soil N in the top 2 ft. on June 2. Samples taken on the same date showed that eight fields in Champaign County that received about 190 lb. of fall-applied N had an average of 279 lb. soil N. Both sets of fields showed some 80 lb. of N more in early June than they had when sampled in late winter (Feb. and March). In contrast, a set of eight fields in Vermilion County that had about 160 lb. N applied in the fall had only 130 lb. of soil N on May 24, slightly less than in March. Soil N is quite consistent among fields in each group, and it’s not clear why there are such differences among the groups.

Can soil N amounts really increase by as much as 80 or 100 lb. in May without any addition of fertilizer N? If we saw this only in a few fields we might think it was sampling error. But we’re finding that soil N often increases as soils warm, and such increases tend to be greater in soils with higher organic matter. So we think this happens as nitrification – the release of N from soil organic matter by microbial action – kicks in as soils warm in the spring. Nitrogen is in the ammonium (NH4+) form when released by mineralization, but then nitrifies (is converted to nitrate NO3) quickly. Both mineralization and nitrification are microbial processes, and rates of both processes are high in warm, moist, aerated soils.

While there are some fields that seem to have less soil N than we might have expected, soil N levels are in general showing amounts at least as high as those we saw at this time in 2015. The largest difference between the two years is rainfall: May rainfall and temperatures were similar both years, but the heavy rain that fell in June, 2015 has not returned in 2016, and is not in the forecast. In fact, rainfall during the first two weeks of June has been below normal over most of the state this year. We think this will be favorable for the crop’s N supply, and expect to see a less pronounced drop in soil N as the 2016 crop moves towards pollination.

Nitrogen management

With warm temperatures and the crop just entering its most rapid growth and N uptake phase, it seems highly likely that, unless soils start to run out of water in the next two weeks, the crop growing in soils with the normal (N rate calculator) amount of fertilizer N will be able to take up most of its N over the next few weeks with little danger of developing N deficiency.

In a trial at Urbana in 2015 with 200 lb. of N applied in April, the crop was at stage V9 and had 45 lb. of N in the plants on June 12. By tasseling time on July 13, it had 159 lb. N per acre in the plants. Soil N between these two dates fell from 240 lb. to 93 lb. per acre, and total (plant plus soil) N fell from 285 to 242 lb. per acre. Rainfall totaled more than 8 inches between these two dates. Even with the drop in soil N to a relatively low level (about 6 ppm nitrate-N and 5 ppm ammonium-N) by pollination, the crop in this treatment yielded 235 bushels per acre.

At the estimated 1 lb. of N taken up for each bushel of yield, the 2015 crop would have taken up about a third of its N after tasseling. Given the low amount of soil N at tasseling, this additional N had to have come from mineralization and, possibly, from N deeper in the soil profile as the crop drew water up during dry weather late in the season. In any case, it’s clear that low soil N at tasseling did not result in low yields due to N deficiency.

It’s premature to draw a strong parallel between the 2015 results and what we might expect this year, but with drier weather this year, soil N levels similar to those we saw in 2015, the crop darker green, and a root system that is likely to be somewhat deeper this year, all signs point to the likelihood of less chance for N loss and deficiency than we saw in 2015. In 2015, yields in most of our trials were high or very high, indicating that N loss and deficiency were not yield-limiting; exceptions were in fields where root damage form standing water was severe, and crops could not fully recover. While this looked like N deficiency, adding more N to such damaged crops often didn’t help very much in 2015.

Despite the dark green color of most Illinois corn fields in mid-June and soil N numbers that show no shortage, we are continuing to hear about producers and retailers gearing up to apply more N, including in some fields that have had a full amount of N applied and where soils have not been saturated this spring. In fields that have already received their full complement of N, with most or all of the N applied this spring, there is no clear justification for adding more N.

This does not appear to be one of those years when “just in case” justifies adding more N fertilizer. It’s highly unlikely that a corn crop that is deep green at knee- to waist-high will experience N deficiency due to lack of soil N. When N deficiency symptoms do develop in late vegetative or reproductive stages, this usually results from the crop’s running short of water to keep photosynthesis going at full speed. What is called “firing” and looks like a shortage of N is really loss of lower leaf area as the plant dries out. As lower leaves start to shut down they move N out to younger parts of the plant (including the ear) to keep the plant going as long as possible. Adding more N neither prevents nor cures this.

If some or all of the N was applied at modest rates last fall or in early spring in an area that has gotten wet several times since, and if soil N sampling shows levels of less than 15 or so ppm of nitrate-N in the top foot (2-ft. samples will capture N that has moved down but aren’t always practical) then adding more N might be indicated. We can’t accurately estimate the chances that applying more N will pay its cost, but if the crop is deep green and growing rapidly despite what seem to be low soil N numbers, that’s a hint that chances of getting a return may not be very high. The crop is always a better indicator of soil N sufficiency at a given growth stage than are soil N tests.

For those heading out to apply more N, remember that applied N has to get to the roots in order to do any good. If we get average rainfall over the next few weeks, that won’t be a problem. But if it stays dry, N is likely to stay close to where it lands in or on the soil. Roots pull water from the surface soil first, and there will need to be enough rain to bring soil moisture levels up to activate roots and to move surface-applied N into the soil before root uptake can resume. Placing N close to the rows in tall corn was only slightly higher-yielding in our trials last year than applying the same amount at normal sidedress time. The soil is a good reservoir for N, and so N applied a month or more before the crop takes it up is usually available. Even in the wet June of 2015 it was neither necessary nor cost-effective to spoon-feed N to the crop. All signs point to even less benefit to that approach in 2016.

Some people are using slowed-release forms of N for applications made at or after the normal sidedress time. When N is applied when crop uptake is close to its maximum, which starts at about the V7 stage, the main risk is that N won’t be released in time for the plant roots to take it up. Any slowing of the release of N increases that risk. Uptake of N remains at a high rate for only about three weeks, and it’s unlikely that N, especially when applied as urea or ammonium, will convert to nitrate and move out of the rooting zone in the few weeks before N uptake starts to slow. That’s especially the case now, with dry soils more common than wet soils, and extended wet periods not in the forecast.


2016 Field Day Events in Illinois

Fields days organized in 2016 by Crop Sciences and Extension at the University of Illinois, Western Illinois University, and Southern Illinois University will focus on crops and pests, with speakers talking about current crop issues along with information from previous research. Each event will offer CEUs for CCAs.

Following is the schedule of crop-related field days for 2016, including locations, dates, starting times, and contact information.

  • Macomb, WIU: Thursday June 23, 12:00 PM; Mark Bernards (309) 313-5917, ml-bernards@wiu.edu
  • Urbana–Weeds, UI: Wednesday June 29, 8:00 AM; Aaron Hager (217) 333-9646, hager@illinois.edu
  • Belleville, SIU: Thursday July 14, 9:00 AM; Ron Krausz (618) 566-4761, rkrausz@siu.edu
  • Monmouth, UI: Friday July 15, 8:00 AM; Angie Peltier (309) 734-1098, apeltier@illinois.edu
  • Perry (Orr Center), UI: Wednesday July 20, 8:00 AM; Mike Vose (217) 236-4911, mvose@illinois.edu
  • Ewing, UI Extension: Thursday July 28, 9:00 AM; Marc Lamczyk (618) 439-3178, lamczyk@illinois.edu
  • Urbana Agronomy Day, UI: Thursday August 18, 7:00 AM; Bob Dunker (217) 244-5444, r-dunker@illinois.edu

Update on Soil Nitrogen

Corn planting has moved ahead of the 5-year average, with 66% of the Illinois crop planted by May 1. Early planting usually means an early start to nitrogen uptake. But N uptake is slow for a month or more after planting: in one study we did in 2015, plants at the 4-leaf stage about five weeks after planting had only 4 pounds of N per acre in the above-ground part of the plant. So there’s time both to get N applied to the crop before it needs it and also time for N in the soil to move out of the rooting zone if it’s in the nitrate form and the weather turns wet.

Soil N after fall N application

Dan Schaefer of IFCA and we have continued to sample soils this spring to see how much N applied as anhydrous ammonia last November remains in the top 2 feet of soil, and how much of this N is still in the ammonium form, hence safe from loss even under wet conditions.

Figure 1 shows soil N recovered from samples taken in mid-April. Fall ammonia applications were made in November at the N rates shown, and all included N-Serve. The three sites on the left are farmer fields, and the three on the right are U of I research centers. At the Logan county site, soil without N fertilizer had 84 lb. of N recovered, and zero-N plots had 64, 48, and 63 lb. N recovered at the Champaign, Warren, and DeKalb County sites, respectively.

Figure 1. Plant-available nitrogen (ammonium plus nitrate) in the top 2 feet of soil from samples taken at six Illinois sites in mid-April, 2016. Fall N was applied in November 2015 as NH3 at the rate indicated for each site, and included N-Serve®.

Figure 1. Plant-available nitrogen (ammonium plus nitrate) in the top 2 feet of soil from samples taken at six Illinois sites in mid-April, 2016. Fall N was applied in November 2015 as NH3 at the rate indicated for each site, and included N-Serve.

Even after subtracting an amount of N in soils without fertilizer, most or all of the N applied as fertilizer last fall was recovered in mid-April sampling. For the three on-farm sites, about half of the recovered N was in ammonium form. The amount of N recovered from three on-farm sites with similar soils in April 2015 was similar to what we found this year, but last spring only about one-third of the recovered N was in the ammonium form. Given the difference between the two winters it’s surprising that more of the N was in the ammonium form this year, but we can take it as good news.

With the exception of DeKalb, amounts of nitrogen recovered at the research center sites were also close to the amount of N applied last fall, and were similar to amounts of N recovered from samples taken in April 2015 at the same sites. The positive from sampling at all six sites is that, after a lot of concern about N loss following warm and sometimes-wet condition this past winter, we aren’t really finding that a lot of the N has been lost. Reports are also that surface water nitrate levels, which were higher than normal in February, have not continued to increase, probably because rainfall and tile flow haven’t been unusually high.

In contrast to what we saw in the on-farm sites this spring, only about one-fourth of the N recovered was in the ammonium form at the research centers, compared to nearly half in the ammonium form in last year’s samples. We don’t have an explanation for the difference between on-farm and research center sites. But unless we get a lot of rainfall, N present as nitrate will remain a ready source of N for the crop.

More unexpected than the high percentage of nitrate we found is the fact that we found so much more N at research center sites in April than we found in February. On April 8 I reported http://bulletin.ipm.illinois.edu/?p=3554 that samples taken from these plots in late February this year showed only about 130 and 160 lb. of N per acre, with about 60 and 43% of the recovered N in the NH4 form at Urbana and Monmouth, respectively. The amount of ammonium-N we recovered changed very little between February and April, dropping from 78 to 60 lb. at Urbana and from 68 to 67 lb. at Monmouth. So the higher amount of soil N we found in April came entirely from the increases in nitrate. I’m at a loss to explain how soil nitrate could increase by 116 and 146 lb. per acre at the two sites over a period of 6 to 8 weeks, with little or no drop in ammonium levels. So I won’t speculate; we can just accept that the N is in the soil and available as the growing season gets underway.

Nitrification inhibitor

In the April 8 Bulletin article cited above I reported that N-Serve® used with fall-applied NH3 had little effect on the amount of soil N or ammonium recovered in February at the Urbana and Monmouth sites. Figure 2 shows the amount of soil N recovered and the percentage of N found as ammonium in the mid-April samples. As we saw in February, adding the inhibitor in the fall gave no consistent effect on either N recovery or the percentage of N as ammonium. That’s not surprising, as the levels of ammonium were already fairly low in February and so there wasn’t much ammonium present to nitrify. We had these two treatments at several other sites, and will report on those results later.

Figure 2. Soil N recovery in mid-April 2016 following application of 200 lb. N per acre as NH3 with and without N-Serve in November 2015.

Figure 2. Soil N recovery in mid-April 2016 following application of 200 lb. N per acre as NH3 with and without N-Serve in November 2015.

Cover crop rye and soil N

Using cereal rye to take up soil N and thereby lower potential for loss is becoming more common. Some are using the cover crop to scavenge residual N following harvest in the fall, and some are planting rye before fall N application, or in some cases even fertilizing the cover crop when it’s planted, to see if this will increase the total amount of N recovered in the spring.

Dennis Bowman, UI Extension educator and Dan Schaefer are managing a cover crop study at the U of I research center near Urbana in which cover crop rye was drilled after harvest of both corn and soybean last fall. These trials received no addition of N before soil and cover crop samples were taken on April 15, 2016 and analyzed for N. The rye was 12 to 18 inches tall at the time of sampling, and its dry weight was 942 lb. per acre following corn and 1,735 lb. per acre following soybean.

With no fertilizer N added, the amount of soil N recovered in mid-April was low – only 56 lb. per acre following soybean and 42 lb. following corn (Figure 3). When the cover crop was present, the amount of N recovered from the soil plus the cover crop rye following corn and soybean was only 9 and 5 lb. per acre higher, respectively, than the amount recovered from the soil without cover crop. The cover crop contained about half of the recovered N following soybean and less than 40% of the N recovered following corn. In both cases the amount of N left in the soil with cover crops present was only about 30 lb. per acre, which is about as low as soil N levels ever get. So the cover crop took up what N it found, but that was not very much. The cover crop residue contained less than 2% N, or less than half that of a well-fertilized cereal rye crop at the same stage. Its C:N ratio was above 20, reflecting this N deficiency.

Figure 3. Recovery of nitrogen at a Champaign County site on April 15, 2016 with and without cover crop rye drilled into corn and soybean crops after harvest in fall 2015. No fertilizer N was applied in these trials.

Figure 3. Recovery of nitrogen at a Champaign County site on April 15, 2016 with and without cover crop rye drilled into corn and soybean crops after harvest in fall 2015. No fertilizer N was applied in these trials.

Dan Schaefer is also managing an on-farm site in Macon County in which fall ammonia was applied at the rate of 175 lb. N with N-Serve. The site was soybeans in 2015, with one field planted to cover crop rye and an adjoining field without cover crop. Soil and cover crop samples were taken on April 8, 2016 and analyzed for N. With the added N, rye growth was excellent, with more than 2,700 lb. of dry weight per acre.

Nitrogen recovery was very high, with 272 lb. of soil N recovered per acre without a cover crop (Figure 4).  Of this amount, 132 lb. per acre (49%) was in the ammonium form. In the field with cover crop rye, a total of 258 lb. N per acre was recovered, slightly less than the amount recovered without cover crop. Of this total, 140 lb., (54%) was in the cover crop, and 128 lb. was in the soil. Of the amount of N in the soil under cover crop, 116 lb. (84%) was ammonium, indicating that the cover crop took up nitrate as it was formed, leaving relatively little in the soil. The cover crop might have taken up some ammonium, but soil under cover crop had only 16 lb. less ammonium-N than soil without cover crop, so ammonium uptake by the rye was minimal.

Figure 4. Recovery of soil and cover crop nitrogen on April 8, 2016, at a Macon County site with and without cover crop rye and with 175 lb. N as ammonia with N-Serve applied in November, 2015.

Figure 4. Recovery of soil and cover crop nitrogen on April 8, 2016, at a Macon County site with and without cover crop rye and with 175 lb. N as ammonia with N-Serve applied in November, 2015.

While having rye take up most of the fall-applied N would seem like a good way to lock in the N and keep it from being lost, this also means that much of the N ends up in a form that will become only slowly available to the corn crop. In early April, the field with cover crop had only 128 lb. of plant-available N, and while this amount may increase some after the cover crop is killed due to mineralization, this soil now has nowhere near as much N as the corn crop will need.

How much of the cover crop’s N will become available to the crop, and when this happens, involves weather, soils, and crop growth, so is highly unpredictable. Some of the N in dead cover crop tissue may still be inorganic (nitrate or ammonium) and this can get into the soil and reach the corn roots relatively quickly. But most of the N is part of proteins and amino acids, and getting it into the soil and to the roots requires microbial activity, with N being released as microbes grow and die off. The cover crop residue in this case had a C:N ratio of only about 10:1, so tieup of N should be minimal as the residue starts to break down. Still, the process by which N cycles through microbes to get to the crop’s roots is neither fast nor complete, and the chances that all of the N will all get to this year’s corn crop in time are not high.

Whether or not fall N was applied, fields with cover crop rye going into corn this spring are likely to have low amounts of N in the seeding zone due to uptake by the rye. Strip-till done in the fall or in the spring reduces the density of rye roots in the planting strip, so should lessen this problem. If corn seed will go into soil close to residue or roots of rye, it may help to add some N in-furrow or close enough to the seed to allow the seedling access to the N soon after emergence. That should help avoid early N deficiency. But if the rye has made a lot of growth, it may be worth considering sampling to measure soil N at sidedress time to see if the supply is adequate, even if enough N was applied last fall.

The work reported here is supported by the Illinois Nutrient Research & Education Council, which administers funds from the Illinois fertilizer checkoff. This support is gratefully acknowledged.


Stripe Rust Observed in Madison County Wheat

Retired commercial agriculture Extension educator Robert Bellm observed stripe rust yesterday in several wheat fields in Madison County (Figure).

Robert Bellm - Madison County 2016Figure. Stripe rust in winter wheat, Madison County, IL, April 20, 2016 (photo credit: Robert Bellm).

Rust pathogens are obligate parasites, meaning that they need a living host in order to survive. Wind and rain systems from further south bring spores to our area. This is why rust sightings in states to the South can help us in Illinois anticipate its arrival. Wet leaves and temperatures below 70 °F favor disease development.

Stripe rust is caused by the fungus Puccinia striiformis. Symptoms of stripe rust begin as chlorotic stripes on the leaf. As lesions develop, the fungus produces spores that can cause secondary infections. These spores, which are yellow to orange in color, develop under the leaf epidermis and swell the leaf tissue into a pustule (blister) which breaks open to reveal the spores (Figure).

Several fungicides are registered for stripe rust management, but the most effective time to apply fungicides is between last leaf emergence and complete head emergence. Applications that occur later are not likely to provide adequate protection. Additionally, caution must be exercised when selecting fungicide active ingredients as fungicides in the strobilurin class can only be applied up to complete heading (Feekes 10.5).

Additional Resources

Fungicide Efficacy for Control of Wheat Diseases – A fact sheet authored by Purdue Extension Plant Pathologist Dr. Kiersten Wise.

Physiological Feekes Growth Stages in Winter Wheat – A diagram and listing of growth stages adapted by Oklahoma State University from an article written in 1954 by E.C. Large.

Management of Wheat Diseases in Illinois – An interactive online course containing content developed by former University of Illinois Extension Plant Pathologist Dr. Carl Bradley. The course content begins with head scab management, but beginning with section 1.28 (accessed through the menu on the left-hand side) covers other wheat diseases including stripe rust.


Spring Nitrogen Management for Corn

Even though the price of nitrogen fertilizer has dropped some in the past year, the lower price of corn means that decisions about N management need to be made carefully, with an eye towards maximizing the return to this critically important input.

The return of dry weather over the past week and the forecast for the coming week has lessened the concern about N loss, though we still need to consider the possibility that some fall-applied anhydrous ammonia might have moved out of the upper part of the soil. If rainfall amounts are average or below-average in the next weeks, some N that has moved down but is still in the soil might still be available to the crop later on.

How much N does the crop need?

The first question on N management is rate – how much N will the crop need, and then, how much of it needs to come from the fertilizer we apply? The generally-accepted rule of thumb is that the crop will take up a total of about 1 pound of N for each bushel of yield. We’ve found a similar number in a few studies we’ve done. We normally expect to find the maximum amount of N in plants at maturity, but depending on how the season ends, plant N might peak a few weeks before maturity.

If we expect yield of 200 bushels per acre and accept that the crop will take up 200 lb. of N, does that mean we will need to apply at least 200 lb. of N? Unless we’re growing the crop hydroponically without soil, or in some growth medium without organic matter, the answer is no. All naturally-developed soils have some organic matter, and many of our more productive soils in Illinois have 3 to 5% organic matter. An acre of soil a foot deep weighs about 4 million pounds, so a soil with 3.5% organic matter in the top foot has about 140,000 lb. of organic matter. About 5% of soil organic matter is N, so this soil would have about 7,000 lb. of organic N in the top foot.

The N in soil organic matter is a tremendously valuable resource, but predicting how much of it will become available to the corn crop each year is not easy. The general rule of thumb is that about 2% of it becomes available, which in our example would be 140 lb. of N per acre. The amount released can range from 1 to 3% per year, depending on soil temperature and moisture, and perhaps to some extent on what microbes are present. And not all of the released N may be available to the crop. Some N is released late in the season after the crop stops taking up N, or into parts of the soil where roots are no longer active. Some released N can also be lost to leaching or denitrification if soils stay wet.

Corn yields without N fertilizer can provide as estimate of how much N the soil provides. In the long-running rotation x N rate trial in place at our Monmouth research center, yields of corn following corn without N fertilizer (treatments stay in the same plots so these haven’t had N for 34 years) between 1983 and 2015 averaged 77, with a range of 25 to 116 bushels per acre. For corn following soybean, the average was 144 bushels per acre, and the range was 91 to 228. Soybean residue doesn’t tie up N, so yield for corn following soybean probably measures N availability better than corn after corn. In that case the soil is providing about 140 lb. N per acre per year, which in that soil is roughly 2% of organic N per year.

How much N needs to come from fertilizer?

A great deal of new data were recently assembled and some older data were removed in order to help update the database used by the N rate calculator http://extension.agron.iastate.edu/soilfertility/nrate.aspx to calculate the N rate expected to provide the maximum return to N (MRTN). A preliminary look at the numbers shows that the MRTN will not change a great deal as a result of adding the new data; our very large Illinois database means that it doesn’t change very fast as new data are added. For corn following soybean in central Illinois, the middle of the MRTN range is around 170 lb. N per acre. It’s similar to that for southern Illinois, and about 20 lb. less than that in northern Illinois. For corn following corn, the MRTN is about 200 lb. N/acre in all of Illinois.

Across hundreds of trials there is surprisingly little correlation between optimum N rate and yield; we have seen trials where 150 lb. of N or less have produced yields above 250 bushels per acre, and some where it took 225 lb. of N to produce yields of 150 bushels per acre. The only reasonable explanation for such a wide range is that the soil sometimes supplies more N than usual, and that sometimes there is either loss of N (from fertilizer N or organic N or both) or some of the N in the soil is unavailable due to such factors as poor root systems or dry soils that keep water from moving to the roots carrying N with it.

Form and timing

While we can precisely control the amount of fertilizer N we apply, its availability is affected by weather, soil, and crop growth, so is also somewhat unpredictable. Form, timing, and placement of N fertilizer all can affect availability, usually in ways that we can understand. For example, ammonium stays on soil exchange sites so moves little in the soil while nitrate can move easily with water. But if it doesn’t rain much, nitrate stays in the soil just fine. So knowing the basics of how different fertilizer materials behave can only take us so far; what really happens to N in the soil is heavily dependent on weather, and our predictions regarding N form and timing are little better than our ability to predict weather.

Although predictions of how fertilizer management affects N availability may not be great, we do think that research over a range of sites and years will help us manage better. We started a fairly large study in 2014, sponsored by the Nutrient Research & Education Council (with funds from the Illinois fertilizer checkoff) to look at the effect of N form, timing, and placement on corn yield. Table 1 shows yields averaged over three sites and two years, 2014 and 2015.

Table 1 Apr 15-16

Yields averaged across treatments were between 213 and 230 at all sites except DeKalb in 2015, which had cool, wet weather and averaged 185 bushels per acre. The 150-lb N rate was chosen to be less that the rate needed to produce the maximum yields, making yield more sensitive to N availability from each treatment. Rainfall between mid-May and late June was somewhat above average at all three sites in 2014 and well above average at all three sites in 2015. So we think that in all of these trials, especially in 2015, the potential for N loss was greater than normal.

Averaged across sites, yields ranged from 208 to 219, or by only 11 bushels per acre. Yield ranges within individual sites were generally larger than this, but individual treatment effects weren’t very consistent over sites, so the overall averages are in a relatively narrow range. The inconsistency among sites shows up in the statistical analysis – the more the rank among treatments changed among sites, the lower the chances of seeing statistical differences, and the larger the difference has to be before we can say it’s due to treatment instead of just to chance.

Even with the variability across sites, there were some treatments that gave higher yields than other treatments. Surprisingly, the two treatments that produced the highest yield (219 bushels per acre) were dry forms: urea with Agrotain® and SuperU®. Both of these contain urease inhibitor and SuperU contains a nitrification inhibitor as well. But statistically, these treatments did not produce higher yields than the check (UAN injected at planting), and in fact none of the first six treatments listed after the check yielded statistically less than the dry treatments or the check. These included delaying all of the N until sidedress time (V5) and split applications with 100 lb UAN at planting and 50 lb applied as UAN at V5 or V9, or urea + Agrotain broadcast at V5. Waiting until V9 to broadcast urea + Agrotain yielded slightly less than the best treatments. Ammonia (NH3) applied early also yielded among the best treatments, but only if it had N-Serve; without N-Serve it yielded a few bushels less.

Only two treatments yielded significantly less than the check – UAN either surface-banded at planting or UAN with Agrotain broadcast at planting. Neither of these is typical; we included them to see how well preserved the N in UAN might be if all applied without injection at planting.

Beginning in 2015 we included treatments with 100 lb. UAN injected at planting and the additional 50 lb. applied as UAN at tasseling time. We applied these as a surface band (dribbled) either in the row middle or into the row. The in-row application yielded more than the mid-row application, but the in-row application did not produce significantly higher yield than the check (UAN injected at planting.)

Conclusions

While we saw some small differences among treatments included in this study, commonly-used timing and forms of N all produced similar yields, even under what we would consider high-loss conditions. This was at an N rate of only 150 lb. N per acre; the higher N rates used by most producers should have provided enough N to the lower-yielding treatments to bring them even closer to the higher yields produced by the better treatments. In fact, the N rate trials included at each site showed that 170 lb. of N per acre, applied as UAN injected at planting, increased yields by an average of 5 bushels per acre compared to 150 lb. of N.

While we would have expected larger differences among yields from these treatments, these results that show that both the risk of N loss and the benefit from delaying some of the N or using inhibitors may be a little less than we’ve thought. Getting data from another year or two will help paint the picture more fully, but these results give some reason to be confident that the N management systems in common use all have good potential to provide the crop with N. Adding costs by changing N management, for example by making another trip over the field to apply late N, may not provide a positive return compared to applying all of the N in one or two earlier trips.

It rained on Easter (March 27) this year, which according to the old adage means rain for the next seven Sundays after that. The warm, dry, sunny day most of us enjoyed on April 17 tells us that won’t happen this year; in fact, the dry pattern that has now been in place for more than a week may persist, even though these is some rain in the forecast. I mention this only as a reminder that some of the N management systems that have been promoted, including late applications of surface-applied N, can mean reduced or delayed availability of fertilizer N to the crop under below-normal rainfall periods. The weather could change, of course, but this is one of the risks, along with increased costs, that increasing the complexity of N management can sometimes bring.


Is Fall-Applied Nitrogen Still Present?

The pattern of warmer and wetter than usual weather this past winter has changed some in the past two months, but hopes for a warm, dry, early spring have faded as well. Concerns remain about how much fall-applied N might have been lost and about whether and how this should change how we manage N this spring.

Most Illinois producers waited until soil temperatures had dropped to 50 degrees or less before applying anhydrous ammonia last fall. Soil temperatures dropped a little slower than normal during November, though, and in a mid-December warm period, soil temperatures approached or exceeded 50 degrees for a few days in much of central and northern Illinois. December rainfall was well above normal, with about 4 inches falling over most of the state right after Christmas. January brought lower temperatures, but tile lines continued to run much of the winter, and above-normal temperatures returned in February and March.

Dan Schaefer of the Illinois Fertilizer and Chemical Association and we in our Nutrient Research & Education Council-funded N tracking research project have been doing some soil sampling this past winter and early spring to see if we can measure how much of the N applied as fertilizer last fall might be gone as a result of the winter conditions. By “gone” I mean no longer found in the top two feet of soil, which is the depth to which we typically sample.

A set of eight fields in Vermilion County that Dan sampled in December, January, and February showed little change in soil N between December and February, though there was some loss of nitrate-N (NO3) between the January and February samples (Figure 1.)  The percentage of recovered N that was in the ammonium form (NH4+) – the form that’s safe from immediate loss due to its binding with negative charges in the soil – actually went up some, which is explained by the loss of nitrate. Samples like these show a fair amount of variability so we can’t make strong statements, but we can’t conclude based on these numbers that a lot of N was lost over the winter.

 

Figure 1. Nitrogen recovered from the top two feet of soil sampled in December, January, and February,  averaged over eight fields in Vermilion County, Illinois. These fields received an average of 163 lb of N as NH3 applied with N-Serve the second week of November 2015.

Figure 1. Nitrogen recovered from the top two feet of soil sampled in December, January, and February, averaged over eight fields in Vermilion County, Illinois. These fields received an average of 163 lb of N as NH3 applied with N-Serve the second week of November 2015.

Samples that we took after November application (of 200 lb of N), in January at Urbana, and in late February at the Urbana and Monmouth research sites showed a considerable drop in soil N at the late February sampling time (Figure 2.) Samples taken after application showed that most of N that was applied was present in the November and (at Urbana) early January sample times, and that some three-quarters of the N was present as ammonium. By late February, however, the amount of N recovered (after subtracting the N recovered from zero-N plots) was about one-third lower than the amount recovered earlier at Monmouth and less than half the amount recovered earlier at Urbana. At neither location did using N-Serve affect the amount of N recovered nor the percentage of recovered N that was in the ammonium form.

Figure 2. Soil N recovery from N-tracking sites at Urbana and Monmouth, Illinois. Nitrogen was applied as NH3 at  200 lb N/acre in November at the first sample date. The late February samples were from treatments with and without N-Serve.

Figure 2. Soil N recovery from N-tracking sites at Urbana and Monmouth, Illinois. Nitrogen was applied as NH3 at 200 lb N/acre in November at the first sample date. The late February samples were from treatments with and without N-Serve.

In a set of fields that Dan Schaefer sampled in Champaign County in early January and again in mid-March, total N recovered did not change much, but only 40% of the N was present as ammonium in March, down from 60% in January (Figure 3.) The fact that some of the ammonium converted to nitrate over this period means that more of the N is now susceptible to loss; the good news is that it is still present in the top two feet of soil.

Figure 3. Soil N recovered averaged over eight Champaign County fields where about 180 lb of N as NH3 was applied in the second week of November, 2015. Seven of the fields had N-Serve applied with the NH3.

Figure 3. Soil N recovered averaged over eight Champaign County fields where about 180 lb of N as NH3 was applied in the second week of November, 2015. Seven of the fields had N-Serve applied with the NH3.

The field included in the averages in Figure 3 that did not receive N-Serve was paired with one that did, allowing us to see if N-Serve affected the amount or form of N recovered. Averaged over the two fields, about the same amount of N was recovered in March as was recovered in January. But in January, the field with N-Serve had 70% of its recovered N as ammonium, compared to 53% ammonium in the N recovered from the field without N-Serve. At the mid-March sampling, the field with N-Serve had 73% of the recovered N as ammonium, while only 39% of the N in the field without N-Serve was in the ammonium form. We need to be cautious because this is from only a few samples, but if these reflect reality then the nitrapyrin did here exactly what it was supposed to do: keep ammonium from converting to nitrate to reduce the amount of N subject to loss. Whether or not that will make a difference in how much N is available to the corn crop depends entirely on what sort of weather, soil, and crop conditions we have up to the time N uptake starts.

We see in the above that sampling soil for recoverable N this past winter gave a mixture of results, ranging from disappearance of more than half of the N from the top two feet of soil to only small changes over time. Adding to the picture is the report that surface waters in some places have reported nitrate levels somewhat higher than normal for this time of year; we would expect this to be coming from tile lines, but some of it could be from N left over at the end of the 2015 season. The percentages of soil N present as ammonium seem to be on the low side of expectations, which could mean considerable potential for loss if the weather is wetter than normal in April and May.

We have little previous experience looking at soil N from fall to spring, so there’s no reason to panic at this point, or to order more fertilizer N to replace what might have disappeared. Our best strategy now is to assume that most of the N we applied last fall is still in the soil, to get the crop planted as conditions allow, and to both monitor the crop and to stay tuned as we continue to monitor soil N up to the time that the crop is taking up N rapidly. The warm and dry spring we hoped for could still materialize, and with it would come low N-loss conditions as well as early uptake of N by a rapidly-developing crop. If the opposite happens, we will still have time to manage N for good yields while minimizing further loss.


Early Registration Open for Bi-State Crop Advantage Conferences

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This January Extension Specialists from both Iowa State University and the University of Illinois will present some of the latest research-based information on crop production and management issues at two Bi-State Crop Advantage Conferences:

January 8 in Burlington, IA and January 29 in Moline, IL.

Certified Crop Advisers can earn up to 6 hours of CEU credit. Re-certification credit is also offered to Iowa private pesticide applicators. Advance registration, no later than one week before the conference, is $50 per person. Late and on-site registration is $60.

 

Click here to view the January 8, 2016, Burlington, IA conference agenda.
Click here to register for the January 8, 2016, Burlington, IA conference.

Click here to view the January 29, Moline, IL conference agenda.
Click here to register for the January 29, Moline, IL conference.