Spring Nitrogen Management

Most corn producers have made plans on how to supply the 2017 Illinois corn crop with nitrogen. But with the stakes high, unusually early N application this past winter and early spring, the delay in fieldwork due to rainfall over the past week, and ongoing pressure to “get nitrogen right,” some might be rethinking plans as the season gets underway.

I presented a webinar on the topic of spring N management on March 30, 2017; the link to the recording can be found at https://ifca.com/. In this article we’ll look at some of the data presented during the webinar and will discuss what these findings mean for spring-applied N. This work is funded by the Illinois Nutrient Research and Education Council, using fertilizer checkoff dollars.

Is fall-applied N still present?

A first question for those who applied N last fall is whether the N is still present and how much of it has been converted to nitrate. Dan Schaefer of IFCA and his group sampled soils at three on-farm sites in mid-November, mid-December, late January, and early March, following application of 200 lb. N as NH3 with and without N-Serve in late October last fall. The amount of N recovered from the top 2 feet of soil hasn’t changed; 240 lb. N was recovered on December 16 and 238 lb. on March 3.

Nitrate as a percentage of the N recovered increased some over the winter, from 55% nitrate in December to 67% nitrate in early March. In 2016, about 60% of recovered N was nitrate when soils were sampled in March, and about 70% was nitrate in April samples. So from what data we have, it appears that, at least in years with relatively mild winters, we can expect more than half of the N to be converted to nitrate by April. Using N-Serve in the fall hasn’t consistently lowered the percentage of nitrate in spring samples, though variability in the samples makes this an imprecise measurement.

Is having most of the fall-applied N in the nitrate form by planting time a problem? Not unless the conditions are conducive to N loss before crop uptake begins. At Urbana, nitrate as a percentage of recovered N reached 80% by early May, and was above 85% by early June in both 2015 and 2016. The amount of soil N recovered stayed constant during May; any N that might have been lost from the soil plus N taken up by the crop didn’t exceed the amount of N provided by mineralization. Most importantly, the N was still there when crop uptake began.

In comparison to fall-applied N, N applied as NH3 before planting in 2016 had low nitrate initially, then nitrate percentage increased steadily through most of May, reaching 80% of recovered N by early June. While this longer retention of ammonium in the soil is a positive in that ammonium doesn’t move and nitrate does, whether or not this affects the amount of N available to the crop in June depends on whether or not soil conditions are favorable for N loss (that is, wet) during May and into early June. If that happens in 2017, our N tracking project should be able to measure changes in soil N, and we’ll make those results available.

Choosing nitrogen rates

While it’s easy to get caught up in questions of N timing and form, we first need to decide how much N to use. The 2016 season brought normal to below-normal June rainfall, little N loss, and high rates of mineralization; as a result, relatively low N rates produced relatively high yields. Adding the 2016 data to the database that powers the N rate calculator (at http://cnrc.agron.iastate.edu/) actually brought the Illinois rates down by a few pounds of N. At current corn and N prices, guideline rates for corn following soybean are 154, 172, and 179 lb N per acre in northern, central, and southern Illinois, respectively, and 200, 200, and 189 lb. N per acre for corn following corn.

The calculator guideline rates and the “profitable” N rate ranges found there represent a good starting point for determining N rate for corn in 2017. The calculator uses actual N response data from hundreds of trials to come up with guideline rates. The calculated rate may not be exactly what is required for a given field, though it takes an N rate trial in the field to know that. Some 60 to 65% of the trials in the database have “best” (most profitable) N rates that are lower than the overall best rate. So an N rate trial in a given field is more likely to show a best rate that’s lower than the guideline calculator rate than it is to show one that’s higher than the guideline rate. Choosing high rates in order to be “safe” carries both economic and environmental costs.

Will the crop run out of N?

One concern that seems to have increased in recent years is the fear that the corn crop will run out of N at some point during the season, even if enough N is applied early. In fact, it’s rare to have the crop run out of N during pollination and later (grainfilling) stages when enough N was applied early in the season and leaves have good color at tasseling time. In 2016, nearly every field had good color at tasseling time.

Any N deficiency symptoms that appear during second half of the season are almost always due to having soils too dry, or, less commonly, too wet; such symptoms almost never come form having too little N in the soil. Water uptake is needed to bring N to the roots and into the plant; under dry conditions, water uptake slows or stops, and so N uptake slows or stops. The “firing” that starts with lower leaves during dry periods is completely due to lack of water, and adding extra N to the soil before the crop fires will do nothing to alleviate it. Only water can fix this problem, and leaf area that fires usually doesn’t come back to healthy green. Under very wet conditions, roots function poorly and may be unable to take up adequate nutrients, including N. Roots standing in water are also unable to sustain the plant in ways unrelated to nutrient supply.

So even if we apply enough N, might the crop still run out of N if yield potential turns out to be higher than expected? Again, we see no evidence of this. The crop typically contains a maximum (a few weeks before maturity) of 0.9 to 1.0 lb. N per bushel of yield, so we know that high yields require that the crop take up more N. But we also know from N rate trials that yields of 225 to 250 bushels are often produced at N rates as low as 150 lb. N per acre or less. The extra N in such fields comes from mineralization of the N contained in soil organic matter. Fields and parts of fields with higher organic matter typically produce higher yields as well as more mineralized N, making it easier for the N needs of the crop to be met. In 2016, we saw yields as high as 180 bushels per acre where no fertilizer N had been applied. It is not at all unusual to have the soil provide 150 lb. or more of N to the crop. In lighter soils with lower organic matter, we would expect this amount to be lower, though yields without fertilizer N can be surprisingly high.

One idea being marketed today is to test or model soil N during vegetative development and to apply more N if the test shows low soil N levels. This seems to make sense, but we don’t have good guidelines to tell us how much N needs to be in the soil at a certain stage of crop development to assure that there’s enough for the rest of the season. Soil N levels drop fairly rapidly as N is taken up by the crop. In 2016, we found that during the 18 days before tasseling, soil N levels dropped by about 3 lb. N per acre per day, to less than 10 ppm nitrate in the top 2 feet of soil, without having the crop ever show deficiency symptoms on the way to high yields. Over this same period, the crop took up almost 6 lb. of N per acre per day, about twice the rate at which soil N disappeared. Mineralization presumably made up the difference. Much of the N in the soil is in the ammonium form, especially when soil N levels are low, so nitrate levels, which are often used to measure soil N, can be as low as 3 or 4 ppm as the corn approaches pollination without any cause for concern.

We know from N uptake studies that some 70% of the crop’s N requirement is taken up by pollination, with uptake rates as high as 6 to 8 lb. N per acre per day right before tasseling, and averaging perhaps 5 lb. N per acre per day for the 30 days before tasseling under good conditions. N uptake rates slow after that, to maybe 2 lb. N per acre per day after pollination to 1 lb. per acre per day or less by mid-grainfill. Mineralization rates may be high enough to supply most of the N the crop needs to take up after pollination, with little need for N supplied (earlier) as fertilizer.

As another way to look at the question of running out of N and the need to apply N late, we conducted N rate studies at several locations in 2016, in which we either applied all of the N at planting or all but 50 lb., which we then applied by dribbling the N solution at the base of the row at tasseling. Figure 1 below shows results from this study at Urbana with corn following soybeans, and Figure 2 for corn following corn. Results were remarkably consistent at the different sites where we had these trials in 2016; optimum N rates and yields at those rates were the same whether we applied all of the N early or kept 50 lb. back to apply late. We may see different results in 2017, but in 2016, keeping back some N to apply into tall corn in mid-season did not cover any of the cost that such an application would incur.

Figure 1. Response to N rate, with N applied either all at planting or all but 50 lb. at planting and 50 lb. dribbled into the row at tasseling. Data are for corn following soybean at Urbana in 2016.

Figure 1. Response to N rate, with N applied either all at planting or all but 50 lb. at planting and 50 lb. dribbled into the row at tasseling. Data are for corn following soybean at Urbana in 2016.

Figure 2. Response to N rate, with N applied either all at planting or all but 50 lb. at planting and 50 lb. dribbled into the row at tasseling. Data are for corn following corn at Urbana in 2016.

Figure 2. Response to N rate, with N applied either all at planting or all but 50 lb. at planting and 50 lb. dribbled into the row at tasseling. Data are for corn following corn at Urbana in 2016.

N form, timing, and additives

A major part of our NREC-funded nitrogen work in the past three years has been an evaluation of different ways to apply N to the corn crop. One part of this was a comparison of fall- and spring-applied N, using anhydrous ammonia over a range of rates. Dan Schaefer of IFCA conducted these studies as replicated, field-scale strips in farmer fields. Over ten site-years, it took 18 more lb. of N (169 versus 151) to produce about one less bushel of yield (219 versus 220) using fall-applied N compared to spring-applied N. At current prices, spring-applied N netted $11 per acre more than fall-applied N at the optimum N rate for each. Those are small differences; using guideline N rates (which are higher than optimum rates we found) would have produce virtually identical yields whether the N was applied in the fall or in the spring. Given that we often see a little more loss of N through drainage tile with fall application, those able to apply in the spring may see small gains in terms of better efficiency and less loss of N.

We also evaluated the effect of applying all of the N as UAN at planting versus a split application, with 50 lb. of N at planting and the rest applied using UAN at sidedress. Averaged over ten site-years, optimum N rates and yields at those rates were very similar for these two methods (Figure 3). Splitting the application required 9 lb. more N and yielded 1.6 bushels more, so netted about $2.50 per acre more than applying all of the N at planting. Unlike the fall- versus spring-applied N study, though, optimum N rates in the sidedress study were a little higher than the guideline (N calculator) rates; using guideline (lower rates) would have given a slight edge to planting-time N.

Figure 3. Response averaged over 10 site-years to N rate, with N applied as injected UAN all at planting or applied at 50 lb. at planting and the remaining N sidedressed as injected UAN at stage V5.

Figure 3. Response averaged over 10 site-years to N rate, with N applied as injected UAN all at planting or applied at 50 lb. at planting and the remaining N sidedressed as injected UAN at stage V5.

As part of N rates studies completed so far at 10 site over 3 years, we applied the same N rate (150 lb. per acre) using a variety of N forms, timing, and additives. Among the 15 treatments in these trials from 2014 through 2016, only 10 bushels per acre separate the highest from the lowest yields (Table 1). The two highest yields came from applying dry urea with Agrotain® (urease inhibitor) or as SuperU® which incorporates both urease and nitrification inhibitors. We did not include urea without an inhibitor, so do not know how much the inhibitors contributed. Other treatments that yielded more than the average included UAN injected at planting (our designated “check” treatment), 100 lb. N at planting followed by 50 lb. UAN, either injected at V5 or dribbled mid-row at V9, and UAN all injected at V5.

Table 1. Yields and yield ranks across 10 site-years, 2014 through 2016, for 15 different times and forms of N used to apply 150 lb. of N per acre. Sites included DeKalb, Monmouth, and Urbana in all three years, and Perry in 2016.

Table 1. Yields and yield ranks across 10 site-years, 2014 through 2016, for 15 different times and forms of N used to apply 150 lb. of N per acre. Sites included DeKalb, Monmouth, and Urbana in all three years, and Perry in 2016.

Yield averages not followed by the same letter are significantly different; seven of the 15 treatments did not yield significantly less than the highest-yielding treatment, and five treatments did not yield statistically more than the lowest-yielding treatment. The lowest-yielding treatments included UAN with Agrotain broadcast at planting; UAN dribbled between rows at planting or at V9; and NH3 injected at or before planting, with or without N-Serve®. As an observation, treatments with lower yields were those that included surface application of UAN or application of N in a way that likely meant some delay before plant roots could get access to the N. There may have been some loss of surface-applied N to volatilization, but N broadcast as UAN on the surface may also not have moved down to the roots quickly.

We added several treatments after 2014, and because the 2015 and 2016 seasons differed considerably in June rainfall, we’ll look at the data for 2015 and 2016 separately, across three sites in 2015 and four sites in 2016. With the inclusion of seven of the ten site-years averaged in Table 1, of course, yield levels and trends were similar to those that included the 2014 date. Only 12 bushels per acre separated the highest- and lowest-yielding treatments, and the designated check (150 lb. N as UAN injected at planting) produced 221 bushels per acre, higher than six of the 19 treatments and not statistically less than the highest-yielding treatment (Table 2).

Table 2. Yield ranks across sites in 2015, 2016, and both years of 19 different times and forms of N to apply 150 lb. of N per acre. Sites included DeKalb, Monmouth, and Urbana in both years, and Perry in 2016.

Table 2. Yield ranks across sites in 2015, 2016, and both years of 19 different times and forms of N to apply 150 lb. of N per acre. Sites included DeKalb, Monmouth, and Urbana in both years, and Perry in 2016.

Of the four treatments added in 2015, UAN with Instinct II® (nitrapyrin) injected at planting produced below-average yields, though not statistically less than that of the check (UAN injected at planting.) The other three added treatments included 100 lb. N as UAN injected at planting followed by split-applying 50 lb. as UAN. Dribbling UAN into the row at V5 was a very good treatment, yielding only 2 bushels less than the highest yield. The last two treatments including dribbling the split N between rows or at the base of the plants at tasseling time; these also yielded well, at 221 and 222 bushels per acre, respectively, about the same as the check (Table 2).

Treatments that ranked considerably higher in 2015 (wet June) than in 2016 (normal to dry June) included 100 lb. N at planting followed by either 50 lb. N injected at V5, or by 50 lb. dribbled into the row at VT; and the treatment with all of the N sidedressed between the rows at V5. It’s possible that rainfall in late May and early June moved the sidedressed N to the plant roots a little sooner in 2015, and it’s also possible that enough planting-time N had moved out of the root zone that year to make adding the last 50 lb. in the row at tasseling a little higher-yielding.

Treatments that ranked considerably higher in 2016 than in 2015 included urea + Agrotain broadcast at planting, ESN broadcast at planting, and 100 lb. N at planting with 50 lb. dribbled between the rows at VT. There was enough rainfall in May of both years to move urea into the soil without too much problem, so it’s not clear why these performed better in 2016. But both were good treatments across all sites. It’s also not very clear why dribbling 50 lb. N down the row middle at tasseling was better in 2016 than dribbling it into the row, the reverse of what we found in 2015. Again, these were both reasonably good treatments, but not better than the check (UAN injected at planting.)

Summing up

Yields levels were relatively consistent among sites and years, ranging from 185 to 248 bushels per acre; we didn’t really see the tough conditions that we know can happen. We also found somewhat lower N responses than we expected; the 150-lb. N rate we chose in order to spread the yields from different N treatments was either more than the optimum N rate or within 20 lb. of the optimum at six of the ten site-years. So the high-loss conditions under which some treatments might be expected to do much better than others were not very noticeable in this study, at least during the first three years.

Given all that can happen when we apply N fertilizer in a way that we think will produce high corn yields, it’s no big surprise that this research has not so far identified clear “winners” or “losers” among the different ways we managed N. With top-to-bottom yield ranges as high as 36 and as low as 12 bushels among sites, expecting treatments to “hold rank” across such different environments may not be very realistic.

The ability to separate yield averages statistically is directly related to how well treatments held rank across sites-years. When a treatment ranks high at some sites and low at others, its overall average is in the middle, and the statistical comparison, which measures how well the results predict future performance, becomes less certain. That’s why so many of the treatment yields averaged over sites (as in Table 1) are followed by the same letter – we can’t be sure that a treatment that yielded 4 or 5 bushels more than another treatment will do that again next time, because it didn’t do that consistently across trials so far.

These results show, though, that just about any way we are managing N now is probably working reasonably well. We did not expect that treatments involving dry urea, protected against loss and broadcast at planting, to perform as well as they did. We don’t think that these results suggest a push towards broadcast urea application, but it is a common practice in many parts of the world, and if costs and availability move us in this direction, it appears to be workable. Treatments that did not do as well as we might have expected included applying UAN solution on top of the soil, whether that was all at planting or at other times. Anhydrous ammonia applied at or before planting also produced lower yields than expected.

These results seem to point to the benefit of having much of the N in the soil into which the roots grow, and to have it there relatively early in the season. Though we didn’t measure soil N in this study, most of the treatments that produced below-average yields were ones that supplied most of the N only at or after the plants had grown for a month or more. Treatments such as UAN dribbled or NH3 injected between rows at planting might have placed the N out of reach of early root growth. In contrast, broadcasting urea or injecting UAN between rows at planting might have resulted in more N in the soil where the roots grew early.

Even if the hypothesis that having more N in the vicinity of the roots holds up in further research, yield differences we found over sites were probably not large enough to justify many changes in how we manage N. As an example, incorporating broadcast UAN, which is normal practice, might be adequate to provide the roots with early access to N. And, if it stays dry for several weeks after planting (which did not happen in these trials), broadcasting urea might not work as well as we saw it work so far.

We might, though, want to consider the need for N near the roots during early growth as we plan N programs. This could be as simple as applying more of the N early and less at sidedress, or of applying sidedress N closer to the row for better access by the roots. As is always the case, weather conditions will have a large influence on how necessary, useful, or successful our best-chosen strategies turn out to be; no responsible N management program is completely safe.

One approach that has appeal, but that adds considerable economic and environmental risk, is to “just apply more” in order to make certain the crop won’t “run out” of N. We have seen how rarely the crop runs out of N when normal N rates are applied. Our work is also showing that loss of N (movement out of the top 2 feet of soil) is less than we expected, especially when we account for the amount taken up by the crop. With the equipment and knowledge we have today, everyone can manage N responsibly and with confidence that the crop will get the N that it needs. As is always the case, good weather helps a great deal to make N work, and we wish good weather for everyone as the season gets underway.

Announcing a nitrogen management webinar

On Thursday, March 30 beginning at 9:00 AM, I will present a webinar summarizing our recent N management research, which is funded by the Illinois Nutrient Research and Education Council (NREC) using fertilizer checkoff funds.

Topics will include the status of N applied last fall, a summary of results from our N form and timing studies over the past three years, and a look at how well soil N tracked through the spring can tell us if we need more N.

You may register for the Spring Nitrogen Management Webinar at:  https://attendee.gotowebinar.com/register/8090182749410833409 After registering, you will receive a confirmation email containing information about joining the webinar. One CEU of NM (nutrient management) CEU will be available.

Planting date for corn and soybeans in Illinois

Relatively dry weather in recent weeks throughout much of Illinois and an early start to fieldwork might provide the unusual opportunity this year of letting us choose corn and soybean planting dates instead of having to wait until it’s dry enough.

There are reports that some corn and possibly some soybeans were planted as early as February this year. The main motivation for such plantings is often the excitement that comes (or doesn’t) from having the crop survive “against all odds.” While that may be satisfying, it doesn’t offer much profit potential. If the crop survives it hardly ever produces yields as high as those from planting at the normal time, and planting very early affects insurability and can also increase the cost of replant seed.

In the warm, dry March of 2012, we planted one date of our planting date study at Urbana on March 16. The crop emerged uniformly and grew well until frost on April 11-12 killed the tops of the plants to the ground. About 75% of the plants survived and grew back, though, and to our surprise this planting also yielded about 75% as much as the April plantings. Most corn planted in mid-March in 2012 (about 5% of the state’s corn was planted by April 1 that year) had to be replanted.

Most people avoid taking insurance coverage risks by planting before earliest allowable planting dates under the federal crop insurance program. Those dates for corn are April 10, April 5, and April 1 for northern, central, and southern Illinois, and for soybean are April 24, April 20, and April 15 in northern, central, and southern Illinois.

Having the earliest insurable dates for soybean about two weeks later than for corn reflects what until recently we considered to be the greater danger from planting soybeans very early compared to planting corn very early. In fact, with better seed handling and treating today, soybean seed produces acceptable stands with mid-April planting about as often as corn does.

Contrary to what many believe, soybean is no more vulnerable to frost than corn after emergence. The only time we’ve seen soybean seedlings killed by frost is when it gets near freezing at the time the hypocotyl hook is exposed to the cold sky, before the cotyledons are pulled from the soil. This period of vulnerability typically lasts no more than a day or two; after the hypocotyl straightens and the cotyledons open, soybean plants are fairly cold-hardy. While corn plants have been considered safe from frost until the growing point is near the soil surface, we have seen corn plants killed by low temperatures (often below 30 degrees) even if they have only two or three leaves exposed.

The primary cause of stand loss in both crops is having heavy rainfall soon after planting. Stand loss from wet soils before or during germination is greater for corn when soil temperatures are low. For soybean, having warm soil under wet conditions speeds up the germination process and mean that seedlings run out of oxygen before emergence. But chances of having heavy rainfall soon after planting are not higher with early planting, and stand problems due to wet soils are as common with May planting as with April planting.

Between 2007 and 2016, we ran planting date studies for corn at a total of 22 Illinois site-years, and between 2010 and 2016, at a total of 26 site-years for soybean. There were four planting dates in each trial, ranging from early April through late May for corn and mid-April through early June for soybean. Data are expressed as percentage of the yield at the highest-yielding date within each site-year.

As shown in Figure 1, planting date responses expressed as percent of maximum yield within each site-year are surprisingly similar for corn and soybean across recent trials. Both crops showed near-maximum yields when planted in mid-April to early May, and yields dropped to 95, 91, and 86% as planting was delayed to May 10, May 20, and May 30, respectively.

Figure 1. Planting date responses over 22 corn and 26 soybean site-years in Illinois.

Figure 1. Planting date responses over 22 corn and 26 soybean site-years in Illinois.

What should we take from the fact that yields of both crops declined at about the same percentage rates as planting was delayed through May? The main message is that we need to give similar priority both crops in terms of getting them planted on time. For those with more than one planter, that may mean planting both crops simultaneously, as fields get ready to plant. Our long-held idea of planting corn first them starting to plant soybean requires rethinking and possible adjustment. At the same time, the penalty for late planting of corn is a little lower once we get to late May and into June compared to that for soybean, so in fields that stay wet longer, soybeans may still be a slightly better choice.

We also see from the data in Figure 1 that neither crop is likely to yield more when planted in early April than when planted in mid- or late April. If fields for both crops are ready to plant in central Illinois on April 6, there are two reasons to plant corn first: 1) it’s insurable; and 2) corn seed is somewhat better able to emerge at high percentage when planted early than is soybean seed.

On the other hand, we generally expect about 85% of soybean seeds and 95% of corn seed to establish plants, so corn can be a little more vulnerable to less-than-desired stands if conditions turn bad after planting. In neither crop, however, would dropping desired stands by 5 percentage points cost much yield.

Finally, we should take care not to be overly influenced by what happened in 2016, a season when growers reported much higher yields from early- compared to late-planted soybeans. Statewide, over the past 20 years or so, the average date by which we get 50% of the crop planted is about May 1 for corn and May 22 for soybean. It would be good if we could move both of those dates up some, and even better if we could move the two dates closer together. Still, with years like 2012 when planting was very early but lack of rain lowered yields by a lot, there’s little relationship between average statewide planting date and average statewide yield.

Most planting delays are due to wet soils, and so are more or less beyond our control. Mudding in either crop, especially in April, is usually a mistake, given the slow rate at which yields for both crops fall as planting is delayed into May, and given the prevent-plant provisions of crop insurance in effect. We should be diligent at starting to plant when all (not just soil) conditions are right, but there’s little reason to panic when planting isn’t as early as we’d like.

Nitrogen in February?

The unseasonably warm and dry weather we have had during February this year has a lot of people applying ammonia, and others considering it. This raises the question of whether or not February is a good time to apply NH3, and also the question about whether or not a nitrification inhibitor (N-Serve) should be included in late-winter applications.

We encourage waiting until soil temperatures are below 50 degrees before making NH3 applications in the fall, and then to use N-Serve to slow conversion of ammonium to nitrate. Although it was several days into November before soil temperatures fell to 50 last fall, most people were patient, and NH3 went on well. We have not had as much wet weather since then that we had in December 2015, but the soil was not frozen for very long in recent months, and tiles lines have been running for some time in most areas.

Along with Dan Schaefer of IFCA, we are working on an N-tracking study funded by the Illinois Nutrient Research & Education Council (NREC) that includes three on-farm sites in central Illinois. We applied 200 lb. N as anhydrous ammonia in late October last fall, both with and without N-Serve. Figure 1 shows the amount of N (ammonium plus nitrate) that we have measured in samples taken in November, December, and late January. These are averages across the three on-farm sites.

Soil N recovered following application of 200 lb. N as NH3 in fall 2016. Data are averages over 3 on-farm sites in central Illinois.

Soil N recovered following application of 200 lb. N as NH3 in fall 2016. Data are averages over 3 on-farm sites in central Illinois.

The variability over time that we see in Figure 1 is normal with such sampling; we can’t say with confidence that amounts recovered changed over sampling dates or with N-Serve. When we recover amounts of N close to the amounts applied like this, we take that as an indication that there hasn’t been a lot of loss of N to date. In fact, we recovered considerably less N in February 2016 than we had applied in fall 2015, but by April we were able to recover the amount we had applied, and by May, after mineralization had kicked in, we recovered more N than we had applied the previous fall.

The percentage of soil N present in the nitrate form is also important, especially this far in advance of crop uptake. As a negatively charged ion, nitrate is not held by the soil, and so it will move freely with water as water moves through the soil, including into tile lines. Figure 2 shows the percentage of the N amounts shown in Figure 1 that was recovered as nitrate. Like soil N, percentage nitrate is not a very precise number, but we can see that nitrate percentages have gone up some since the fall but do not seem to be changing very quickly, and that N-Serve might be slowing this conversion to a small degree. At the same time, with more than half of the N now in nitrate form, and with soil temperatures above normal now, it is likely that most of the fall-applied N will be nitrate by May, if not earlier.

Figure 2. Percentage of recovered N (from Figure 1) that was recovered in the nitrate form.

Figure 2. Percentage of recovered N (from Figure 1) that was recovered in the nitrate form.

Does this mean we should hold off applying if soil temperatures rise to the upper 40s or lower 50s in February? If soil conditions are good, I don’t see a good reason to wait. For those who prefer to wait, soils dry now means a better chance of being able to apply NH3 with good soil conditions later in the spring. Nitrogen applied as NH3 converts to ammonium quickly, and ammonium will stay in the soil where it was applied. Nitrification (conversion of ammonium to nitrate) is a biological process, and while its rate is low when soil temperatures are in the 40s, it is not zero. So the earlier we apply NH3, the greater the chance that it will be converted to nitrate by the time soils warm and the crop is growing in the spring. Using N-Serve will slow this conversion, and is likely to be as effective used with NH3 applied in February or March as it is when used with fall-applied NH3.

Whether or not the conversion of ammonium to nitrate is a negative depends on the amount of rain that falls between the time nitrate forms (which depends on time and soil temperatures following application) and when crop uptake of N starts in early June. In the spring of 2016, nearly all of the fall-applied N was nitrate by early May, while very little of the N following spring application of NH3 was nitrate; but without loss conditions, the N from both treatments was fully available to the crop in June. We did not see excessive loss of N in the spring of 2015, even though June was much wetter than normal. That’s in part due to the fact that May 2015 was not wetter than normal, so the N was there in early June, and the crop was able to take it up before it was lost. If we happen to get wet weather in April or May, there could be substantial loss of nitrate, whether we applied it last fall or we wait until April to apply.

February 28: Soil Fertility Seminar to offer continuing education

Soil fertility, crop production practices and environmental stewardship will be the foci of a Soil Fertility Seminar on February 28, 2017 in 18 different University of Illinois Extension county offices.

Presentations will be delivered through web conferencing from 9 a.m. to 2:30 p.m.

Topics and speakers will include:

  • Increasing importance of sulfur for field crops–Dr. John Sawyer, Iowa State University
  • Illinois NREC: What have we learned?–Dr. Robert Hoeft, Illinois Nutrient Research & Education Council
  • Managing Nitrogen to Improve Efficiency–Dr. Emerson Nafziger, University of Illinois
  • Tile Nitrate Loss: Effect of fertilizer N application method and cover crops–Lowell Gentry, University of Illinois
  • N and P retention as influenced by tillage and cover crops in a corn-soybean rotation–Dr. Maria Villamil, University of Illinois

Registration costs $50 per person, which includes lunch. Certified crop advisors may earn up to five nutrient management credits.

To view a list of participating counties, a detailed agenda and to register, please visit the Soil Fertility Seminar Webpage.

Please note that the registration deadline may vary by county.

Extension Bi-State Crops Conferences in and near Western Illinois

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


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

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

Hosts: Iowa State University and University of Illinois Extension

More Information: Click here to access the flier.

Online Registration: Click here to register


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

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

Hosts: Iowa State University and University of Illinois Extension

More Information: Click here to access the flier.

Online Registration: Click here to register.


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

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

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

More Information: Click here to access the flier.

Online Registration: Click here to register.

2016 SDS Commercial Variety Test Results Available

SDS Variety Report

This past growing season personnel from Southern Illinois University, Iowa State University and University of Illinois evaluated more than 580 soybean varieties from 22 seed companies in USB-sponsored sudden death syndrome (SDS) variety trials. The varieties that were evaluated ranged from the very early (MG 0) to late (MG V) maturity groups. Maturity groups were divided into early and late categories; for example, MG II was split into early (2.0 to 2.4) and late (2.5 to 2.9) categories in order to more easily monitor crop development and assess disease at the appropriate growth stage (Figure).

Figure. Aerial picture of the 2016 Commercial SDS Variety Trial at the Northwestern Illinois Ag R&D Center in Monmouth. The difference in variety maturity is evident in this picture. Moving left to right are varieties in Early MG II, Late MG II, Early MG III and Late MG III.

Figure. Aerial picture of the 2016 Commercial SDS Variety Trial at the Northwestern Illinois Ag R&D Center in Monmouth. The difference in variety maturity is evident in this picture. Moving left to right are varieties in Early MG II, Late MG II, Early MG III and Late MG III.

At one or more locations in Illinois and/or Iowa each variety within a maturity group category was randomly assigned to a two-row plot within a block (replication); each variety was planted in three replications. Production of the crop within these trials followed university Extension recommendations and was similar to soybeans produced in any Midwestern farm field with a couple of exceptions: 1) to provide a disease-favorable environment irrigation water (where available) supplemented rainfall, and 2) to increase the chance that germinating seedlings would be exposed to the pathogen, at planting time sorghum seed infested with Fusarium virguliforme, the fungus that causes SDS, was placed in-furrow.

Plots were monitored throughout the growing season for growth and development. At the R6 or full seed growth stage, disease incidence and severity ratings were collected for each plot. In each maturity group category, varieties known to have high levels of SDS resistance or susceptibility were included as ‘checks’. Sufficient disease in the susceptible check varieties was required in order for data from a particular trial to be included in the final report.

The final report is available for download here.

While the data may be of use to crop producers to use as a reference when making their 2017 seed selections or for crop advisors or seed company representatives to use when advising their clients, the final report is forthcoming with its limitations:

“Data presented here is from a single year at one or two locations. Varieties may perform differently in other environments.”

“Plots were not harvested for yield in this program because yield comparisons can be misleading from disease nurseries utilizing small plots. Accurate yield data for commercial varieties should be obtained from state variety trials.”

Registration is now open for the 2017 Regional Illinois Crop Management Conferences

Registration is open for the 2017 Crop Management Conferences. These regional conferences provide a forum for discussion and interaction between participants and university researchers and are designed to address a wide array of topics pertinent to crop production in Illinois: crop management, pest management, nutrient management, soil and water management.

Certified Crop Advisers can earn up to 8 hours of continuing education credit. Advance registration, no later than one week before each conference, is $100 per person. Late and on-site registration is $120. Dates and locations along with links to location-specific agendas and online registration are listed below.

Conference topics include:

  • Updating Grain P and K Removal Levels – Dr.  Emerson Nafziger, University of Illinois, Extension Agronomist, Department of Crop Sciences
  •  Crop Management Strategies for Leaner Times – Dr. Gary Schnitkey, University of Illinois, Extension Economist, Department of Agriculture and Consumer Economics
  •  Increasing the Odds of Success: Integrating Weed Management Strategies – Dr. Aaron Hager, Univ. of Illinois, Extension Weed Scientist, Department of Crop Sciences or Dr. Bob Hartzler, Iowa State Univ., Prof. Weed Science or Dr. Karla Gage, Southern Illinois Univ., Asst. Prof. Plant Biology
  •  Is record-setting weather the ‘new normal’? – Dr. Jim Angel, Illinois State Climatologist, Illinois State Water Survey
  •  Management Practices to Reduce Tile Nitrate Loading – Lowell Gentry, University of Illinois, Senior Research Specialist, Department of Natural Resources & Environmental Sciences
  •  The living soil: Crop management, organic matter and soil biology – Dr. Michelle Wander, University of Illinois, Prof. Soil Fertility & Ecology, Department of Natural Resources & Environmental Sciences
  •  Predicting Insect Pressure: Surveys and Web-based Tools – Kelly Estes, Cooperative Agricultural Pest Survey Coordinator, Prairie Research Institute
  •  New Bacteria to Perennial Fungi: Revisiting Crop Disease in 2016 – Angie Peltier, University of Illinois, Extension Educator


January 18: Mt. Vernon – Krieger/Holiday Inn Convention Center. Click here to view the Mt. Vernon agenda. Click here to register for the Mt. Vernon location. For more information, contact Angie Peltier: (309) 734-1098, apeltier@illinois.edu.

January 25: Springfield – Brookens Auditorium – University of Illinois-Springfield. Click here to view the Springfield agenda. Click here to register for the Springfield location. For more information, contact Angie Peltier: (309) 734-1098, apeltier@illinois.edu.

February 1:  Champaign – i-Hotel and Conference Center. Click here to view the Champaign agenda. Click here to register for the Champaign location. For more information, contact Dennis Bowman: (217) 244-0851, ndbowman@illinois.edu.

February 15: Malta – Kishwaukee College Conference Center. Click here to view the Malta agenda. Click here to register for the Malta location. For more information, contact Russ Higgins: (815) 274-1343, rahiggin@illinois.edu.

Mail-in registrations must arrive one week before each conference in order to take advantage of the advance registration discount. To download the mail-in registration form, click here.


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.