2014 Field Day Events in Illinois

Fields days organized by Crop Sciences and Extension at the University of Illinois and by other institutions 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 2014 field days organized by University of Illinois Crop Sciences and by several other institutions.

Event Date – start time Food Contact
Urbana – Weeds June 25 – 8:00 AM lunch Doug Maxwell (217) 265-0344  dmaxwell@illinois.edu
Macomb – WIUa June 26 – 12:00 N lunch Mark Bernards (309) 313-5917 ml-bernards@wiu.edu
DeKalb July 10 – 9:00 AM lunch Russ Higgins (815) 274-1343  rahiggin@illinois.edu
Belleville – SIUb July 10 – 9:00 AM lunch Ron Krausz (618) 566-4761 rkrausz@siu.edu
Monmouth July 15 – 8:00 AM snack Angie Peltier (309) 734-5161 apeltier@illinois.edu
Orr Center, Perry July 16 – 9:00 AM lunch Mike Vose (271) 236-4911  mvose@illinois.edu
Brownstown August 6 – 8:00 AM lunch Robert Bellm (618) 427-3349  rcbellm@illinois.edu
Dixon Springs August 7 – 9:00 AM lunch John Pike (618) 695-2790  jpike@illinois.edu
Urbana August 14 – 7:00 AM lunch Bob Dunker (217) 244-5444 r-dunker@illinois.edu
Ewingc Sept. 11 – 9:00 AM lunch Mark Lamczyk (618) 439-3178  lamczyk@illinois.edu
aWestern Illinois University conducts this field day at its Macomb research farm.
bBelleville is a research center operated by Southern Illinois University–Carbondale.
cEwing Field is operated by University of Illinois Extension in southern Illinois.


Do Soybeans Need N Fertilizer?

There has been a great deal of interest in recent months in the idea of using nitrogen fertilizer during the growing season to increase soybean yields. This is somewhat surprising given that there has been so little evidence from published and unpublished reports showing that this practice increases yields, let alone provides a return on the cost of doing this.

Soybean plants in virtually every Illinois field produce nodules when roots are infected by Bradyrhizobium bacteria, and bacteria growing inside these nodules are fed by sugars coming from the plant. In one of the more amazing feats in nature, these bacteria are able to break the very strong chemical bond between N atoms in atmospheric N2 (N2 makes up some 78% of the air, but is inert in that form.) This “fixed” N is available to the plant to support growth.

The soybean crop has a high requirement for N; the crop takes up nearly 5 lb of N per bushel, and about 75% of that is removed in the harvested crop. It is generally estimated that, in soils such as those in Illinois, N fixation provides 50 to 60% of the N needed by the soybean crop. A small amount of N comes from atmospheric deposition, including some fixed by lightning. The rest comes from the soil, either from that left over from fertilizing the previous corn crop or from soil organic matter mineralization carried out by soil microbes.

Nitrogen fixation takes a considerable amount of energy in the form of sugars produced by photosynthesis in the crop. Estimates of the amount of energy this takes range widely, but could be in the vicinity of 10% of the energy captured in photosynthesis, at least during part of the season. Because photosynthesis also powers growth and yield, it seems logical that, especially at high yield levels, the crop might not be able to produce enough sugars to go around, and that either yields will suffer or N fixation will be reduced. Might adding fertilizer N fix this problem, resulting in higher yields?

We’ve added fertilizer N in a series of trials over the past several years, with some of the research funded by the Illinois Soybean Association. These studies involve application of urea, in some cases with Agrotain® (urease inhibitor) or as ESN (slow-release N) during mid-season, usually in July. Figure 1 shows the result of 22 such comparisons between 2010 and 2013.

Figure 1. Response of soybean to N fertilizer in 22 Illinois trials, 2010-2013.

Yields ranged widely among these studies, but in only one case did adding N fertilizer significantly increase yield (by 6 bushels per acre) and there was no relationship between yield level and response to fertilizer N. With yields as high as 80 bushels per acre, these results provide no support for the idea that the higher the yield, the more response to fertilizer N. In fact, yields above 70 seemed more likely to show yield decreases from adding N, though these differences were small and not statistically significant.

While these results don’t prove that adding N fertilizer doesn’t increase soybean yields, it clearly shows that we can’t count on such an increase, and it certainly calls into question the wisdom of making such applications, at least with our current state of understanding. It is possible that soils often contain more N than we realize, especially under good mineralization conditions, which are also good growing conditions. It is also possible that we don’t really understand the photosynthetic capacity of soybeans under field conditions, and that our guess that yield is limited by photosynthetic rates when the plant is also fixing its own N is just incorrect.

The usual signal of N deficiency in crops – light-green leaves – is rarely seen in soybean plants during the period of podsetting and seedfilling, unless the crop is under prolonged drought stress. Late in seedfilling, leaves start to mobilize their N as chlorophyll and photosynthetic proteins break down, and much of this N moves to pods and into seeds as photosynthesis winds down. If there were a way to get more N into the leaves early in this process, it might be possible to maintain photosynthesis a bit longer and move more material into seeds. It is clear that getting this to happen consistently will be difficult, especially under an unpredictable water supply.

Until and unless we find a way to learn to make N application to soybeans work consistently, or in most cases to work at all, this practice increases both economic and environmental risk. Under dry late-season conditions such as we experienced in 2013, much of the N we apply will stay in the soil, and become part of the mobile pool of soil N going into the fall.

One way to get a better look at this over a wide range of fields and soils is to put strips trials in farm fields. These can be done using aerial or ground application, but ground application is easier to track, if more difficult to do. If you have interest in running such a trial, I’ll be glad to suggest a design.


Webinar to Focus on Nitrogen

While dry weather is allowing N application to start in some places in Illinois, the ongoing cool temperatures continue to raise questions about N management this spring.

With help from the Council on Best Management Practices (C-BMP), we are organizing a webinar for Thursday, March 27 at 8:00 AM to address some of these issues, including fate of fall-applied N, use of inhibitors this spring, and how cool soils might affect soil N supply and plant uptake.

We will also during this time describe a program, newly funded by the Nutrient Research & Education Council, to conduct field-scale N rate trials in several dozen fields across Illinois in 2014. Producers interested in hosting such a trial are invited to attend to learn more.

Sign up for the webinar at https://www2.gotomeeting.com/register/460818786


Cover Crop Field Day March 28th at the Ewing Demonstration Center

Hearing a lot about cover crops lately but unsure if or how they will work for you? Then plan to attend the Cover Crop Field Day at the University of Illinois Extension Ewing Demonstration Center on March 28, 2014 starting at 10 AM.  The field day offers the latest information on cover crops uses – from livestock grazing, soil erosion and compaction reduction, increasing soil organic matter, to increasing future nutrient availability.

Topics for the tour include:

–          Cover Crop Termination, Mike Plumer, private consultant

–          Cover Crop Success and Failures, Panel Discussion

–          New Farm Bill, FSA Update, Bruce Morrison, Hamilton Co. FSA

–          Tour of Cover Crop Plots at EDC, Nathan Johanning, Extension Educator,  Small Farms and Local Foods.

The center is located  north of Ewing, IL (Ewing is about 20 minutes south of Mt. Vernon) on the North Ewing Rd. (watch for signs).  Ewing Demonstration Center started as a soil fertility experiment farm and has been in existence for over 100 years.

This program is free of charge and will start promptly at 10 AM, rain or shine, so dress appropriately.  A light lunch will be provided.  For questions or to register contact Marc Lamczyk U of I Extension, Franklin Co. at 439-3178.

 

Nathan R. Johanning

Extension Educator, Local Food Systems and Small Farms

University of Illinois Extension, Unit 26 serving Franklin, Jackson, Perry, Randolph, and Williamson Counties

402 Ava Rd.

Murphysboro, IL  62966

Phone:  (618)687-1727  Fax:  (618)687-1612

http://web.extension.illinois.edu/smallfarm/

 


Soil Temperatures and Spring Prospects

We hope that we’ve seen the last of the snow by now, but both air and soil temperatures remain below average in Illinois heading into the second half of March. According to the Illinois State Water Survey (http://www.isws.illinois.edu/warm/soiltemp.asp) minimum temperatures 4 inches deep under bare soil ranged from the low 30s in northern Illinois to the mid-30s in southern Illinois the morning of March 17, and with some sunshine on that day, reached the upper 40s to low 50w in southern Illinois but did not get above the low 30s in the northern part of the state.

Soils froze deeper than normal this past winter, and stayed cold into March; frost is only now disappearing in the northern parts of Illinois, which accounts for their staying cold during a sunny day. Hopes that such deep freezing will relieve soil compaction from last year may not be realized; while repeated freezing and thawing result in repeated formation of ice crystals that force soil particles apart, soils that stay frozen don’t repeat this cycle often enough to do much good. The freezing and thawing of the surface soils that we’re seeing now will help loosen them some, but we can’t expect that effect to extend more than a few inches deep.

Though having soil temperatures only in the 30s this late in March is somewhat unusual, March soil temperatures are variable over years. At Champaign, March soil temperatures at 4 inches deep have ranged over the past five years from an average of 36/39 (minimum/maximum) in 2013 to 60/66 in 2011. Rainfall totals ranged from 1.47 inches in 2013 to 5.38 inches in 2011. The start and progress of planting were delayed in both 2011 and 2013, but that was based more on April rainfall than on conditions in March.

When it comes to getting soils to dry out, is warm and wet better or worse than cold and dry? Because water has a higher heat capacity than soil mineral matter, cold soils do not dry out very fast, and wet soils do not warm up very fast. We have seen some of the standing water in fields drain out this past week as soils thaw, but the drying process will be very slow until soil temperatures start to increase. Water loss rates are affected by soil texture and water content, but we would expect wet soil to lose 0.1 inch or so of water in a day if average soil temperature is 40, and at least twice that amount if the average soil temperature is 60 degrees. So having soils warm up is the key to enabling them dry out, though of course it has to stop raining for soils to dry.

Though having low soil temperatures at this point in March does not produce a lot of optimism that planting will start early, it is also not a very good predictor about how the spring will go, or of what kind of season we’ll have. If we’ve learned anything in recent years, it’s that what happens during the summer matters much more than what happens in March and April. We simply need to be ready to do fieldwork and plant as soon as conditions permit.

The likely delay in the start of field work this year may mean re-prioritizing operations once soils dry out. It has been common in wetter springs for the application of anhydrous ammonia to get underway before soils are considered fit to till or plant. That worked OK last year, when soil compaction, due to weather patterns, did not cause much problem for the crop. But we can’t count on that, and compaction from applying fertilizer or doing tillage in wet soils can leaves soils in worse condition than before, even if the surface looks a little drier afterwards.

As a reminder, planting in early April almost never produces yields higher than planting in late April, and can lower yields, even when stands are good. That being said, planting in early April into good soil conditions, with soil temperatures expected to be on the rise after planting, is a sound practice, especially when there are a lot of acres to plant and starting early is the only way to finish on time. But “mudding” corn into wet or marginally wet but cool soil conditions in early April is almost always a bad idea, with considerably more potential to do harm than to do good.

On the lighter side, I’m interested when I hear people say that they usually don’t start to plant until after Easter. Easter falls on the first Sunday after the first full moon after the spring equinox, so ranges between about March 23 and April 24. Easter was on March 31 in 2013 and it was wet until after Easter, so that wasn’t a factor. Easter is on April 20 this year, and we hope that soils get in shape to plant before that. If that happens, I imagine that some might want to set aside their hesitation to plant before Easter, as many did on 2012, when Easter fell on April 8 and we had some 20% of the state’s crop planted by then.


Yield Loss on the Edge of Corn Fields in 2013

We have been receiving reports since corn harvest began this fall about an unusual phenomenon: yields of the outside 8 to 24 rows on the south or west edges of corn fields show lower or much lower yields than corn farther into the field. The damage tends to be relatively uniform down or across the field, and is on field edges that border a soybean field, road, ditch, or another short-growing crop (such as forage legumes or grasses) other than corn. Ears in affected rows are shortened, pinched (missing some rounds of kernels), or they have scattered kernels. We don’t have a good idea of how many fields or acres were affected, but have had reports of this over a fairly wide area in Illinois.

Relatively uniform damage across the end or side of fields downwind of prevailing winds, next to adjoining fields of a different crop or anything else that was shorter in height than the damaged crop, is typically an easy call: this pattern points to something sprayed on adjoining or nearby fields, under windy conditions or conditions that led to drift, of something to which the affected crop was very sensitive. The taller crop – in this case corn – slows air movement and allows the material to settle out, with damage diminishing as one moves into the field.

Corn ear development is initiated at about stage V6, and the uppermost ear starts to develop quickly after stage V10 or so, reaching its peak at about V12-V13, when plants are 5 to 6 feet tall. A number of chemicals can cause ear shortening or disruption of kernel initials, and that that reach the ear during this stage can do damage. Scattered kernels can also result from problems at pollination, but when pollination conditions are as good as they were in 2013, it’s much more likely that this came from something that reached the ear before tassels emerged. Most of the corn was planted in mid-May this past season, and reached damage-sensitive stages in late June or early July. It’s likely that most of the damage took place during that period. By the time the crop pollinated, it would have been too late to get cob and ear shortening.

Some have suggested that the outside rows of corn were damaged when they took the brunt of dry, windy conditions before or during pollination. There are several reasons why this does not explain very well what we saw in 2013. One is that the outside rows in a corn field have access to water and light from outside the field, and tend to yield more, not less, than interior rows under stress conditions. Another clue is the fact that most affected plants tended to be of normal height this year, and if stress had occurred in time to damage developing ears, plants would likely have been shortened at least to some extent.

The main reason for questioning weather-related stress as a cause for this problem is that we didn’t have stress conditions in late June and early July. July temperatures were below normal, with 12 days having high temperatures less than 80 degrees here at Champaign, only 5 days at or above 90, and the high temperature for the month of only 93 degrees. There was little or no water stress until well into August. I believe it’s more likely that the unusually cool conditions somehow made corn plants more physiologically sensitive to whatever might have drifted into fields than it is that high temperatures and winds caused these symptoms by increasing stress.

In terms of timing, soybeans were planted even later than corn, and it’s very likely that the last applications on soybeans took place in July, in some cases when ear development was occurring and the plant was subject to damage like we saw. The fact that we saw damage in some cases where soybeans sprayed around this time were across the road or some distance away tells us that trying to pin down exactly when (and from where) this happened may be difficult.

What moved into fields to cause this damage is likewise not going to be easy to identify after the fact. Glyphosate is part of most late post applications on soybean, and scattered kernels are characteristic of glyphosate applied (off-label) in late vegetative stage, before tasseling. But many applications also contain other herbicides that can cause injury to corn, and we showed several years ago that even nonionic surfactant (NIS) by itself can shorten ears and cause substantial yield losses. So any of several products sprayed, under conditions windier than normal and to corn with ear formation underway and sensitive to damage, could have contributed.

One additional possibility is that aerial application of fungicide and insecticide, perhaps made to soybeans, might have moved into non-target fields and caused this damage. Based on what we saw several years ago, these products by themselves are unlikely to produce damage like this on corn. Adding NIS can make such applications capable of damaging corn, but adding NIS with corn fungicide generally is no longer on the label for pre-tassel applications, and most such applications made to soybeans were made later than this.

It’s likely that this damage, given that it affected only some fields, was unusually severe in some cases, and came during a season with late-planted crops and unusual stretches of cool weather in mid-season, will not often repeat itself. We have seen it before, however, and it certainly makes sense to do what we can to lessen the chance of damage. The first thing is to not apply when wind speeds are too high. We need to be especially careful when using herbicides or other products that can damage corn at low concentrations in fields next to corn, especially when corn is between head-high and silking, and is downwind from fields being sprayed.

The other lesson that we can take from this is to perhaps check fields a little more carefully to try to find such problems before harvest. This wouldn’t have helped prevent this, but it could have provided clues to help prevent it next time.

 


The Surprising 2013 Soybean Crop

The 2013 growing season in Illinois was wet early with delayed crop planting, good rainfall in June and July, mostly cool conditions in July, and little rainfall in August and September, with some high temperatures in late August and in September. With late planting and cool weather at times in mid-summer, seedfillling began only in mid-August, 10 days to 2 weeks later than normal, and took place during a period of very little rainfall. Our expectation for such a season, especially after the dry early-wet late season that revived the crop in 2012, is for a season like 2013 to be a mediocre or even poor one for soybean yields.

But Illinois soybean yields in 2013 surprised nearly everyone: harvest was delayed, seeds filled well, and the average yield for Illinois, according to the November 1 estimate, is expected to be 49 bushels per acre. This compares to 43 bushels per acre in 2012, and if it holds up it will be the third-highest on record, below 50.5 bushels in 2004 and 51.5 bushels in 2011.

Planting date:

Statewide, soybeans were planted late or very late in 2013, reaching 50% planted only about June 1. Results from our trials showed that yield loss from late planting in 2013 was less than we have found in recent years; planting in late May or early June this year produced nearly the same yields as planting in late April or early May. In previous work we have found more advantage to early planting when yield levels are high. We did not see this in 2013; in fact, at the highest-yielding site there was almost no planting date response.

Results in 2013 don’t change the fact that planting early when conditions permit is sound management. But we did learn that a good start to the season can help overcome late-season stress, and that having the crop in good shape at the start of seedfilling might be more important than simply planting early. With such low late-season rainfall, it’s likely that the temperatures in 2013 extended the flowering process and pushed seedfilling into a more favorable part of the season, regardless of when the crop was planted.

Row spacing:

Averaged across sites, soybeans in 15-inch rows outyielded those in 30-inch rows by nearly 4 bushels per acre in 2013. This is about double the response we saw over the previous three years. With reasonably good (though delayed) canopy development in the 2013 crop, we expected that narrow rows might be more valuable for late-planted soybeans. Some of the larger responses did come at later plantings, but this was not consistent among sites. So while we think that it helps that early-planted soybeans develop their canopy earlier, it’s clear that when the canopy “closes” on soybean is not the only thing that matters in setting yield potential.

Fungicide and insecticide:

We found less yield response to foliar fungicide-insecticide applications in 2013 than we have seen in most recent years; the average yield increase was less than 1 bushel, and the response was statistically significant at only one of six sites of our sites. With few diseases or insects to control, we often do not have a good explanation for why such yield increases are sometimes seen, though some have claimed that fungicides can increase yields by reducing stress effects. In 2013, either such stress did not occur while fungicides were still present in the plant or this effect simply didn’t kick in.

Combinations of inputs:

In recent years we’ve been conducting a series of “high-yield” trials in which we use 15-inch rows and combinations of inputs – micronutrients, nitrogen fertilizer, fungicide/insecticide, growth regulators, and lactofen (Cobra®) herbicide – combinations that have been promoted as a key to increasing soybean yields. Among three locations in 2013, yields ranged from nearly 90 bushels per acre to less than half that. At the low-yielding site (Brownstown), adding some of these inputs increased yields by 3 to 4 bushels per acre. But at the highest-yielding site (Urbana), the only effect we found was from use of Cobra®, which reduced yield by nearly 10 bushels per acre. These results are not inconsistent with those from previous years and other locations. It is clear by now that using herbicides like lactofen is more likely to reduce soybean yields than to increase them.

Nitrogen:

Use of nitrogen fertilizer continues to be promoted for soybeans, with the reasoning being that a crop that produces very high yields won’t be able to provide the resources needed to fix enough N for full crop yield. In 2013, as in previous years, we were unable to increase soybean yields by application of fertilizer N during the season. Yields in these trials have ranged from less than 40 to about 90 bushels per acre, and N fertilizer has produced no response regardless of yield level. We haven’t given up on looking for ways that N fertilizer might be used to increase yields, but we think that this might involve a new approach, perhaps looking for signals from the crop that indicate a need for N before it is applied.

Irrigation:

In the past two years we have run a trial at Urbana in which we irrigate soybeans, along with adding in-season N fertilizer and fungicide+insecticide. Under the very dry conditions of 2012, irrigating soybeans, mostly in July and August, increased yield from 70 to 83 bushels per acre. In 2013, it was drier late in the season than in 2012, and application of a total of 7 inches of water in August and September this year increased yield by 9 bushels, from 64 to 73 bushels per acre. Fungicide/insecticide increased yield by about 4 bushels per acre with or without irrigation in 2013, but fertilizer N produced no response regardless of irrigation.

Lessons:

We often like to think (and say) that research results from “odd” years don’t teach us much, since we don’t expect such years very often, so can’t manage based on these results. I disagree – every season and every site tells us something about the crop and how it responds to what we do. If nothing else, we get an idea from such studies about how often, not just how much, inputs will provide a response. We often can only speculate about reasons for things turning out differently than we expected, but that’s part of the learning process.

The Illinois Soybean Association supported much of this research, for which I’m grateful. I’ll be addressing the topic of getting high soybeans yields at the 2014 Corn and Soybean Classics, and hope to see everyone there.

 


2014 Illinois Crop Management Conferences Registration Now Open

The latest research information on crop production and management issues will be discussed at four University of Illinois Crop Management Conferences this winter. These two-day conferences are designed to address a wide array of topics pertinent to crop production, pest management, and natural resource issues and provide a forum for discussion and interaction between participants and university researchers.

Certified Crop Advisers can earn up to 13 hours of CEU credit. Advance registration, no later than one week before each conference, is $130 per person. Late and on-site registration is $150. Dates and location for the four regional conferences are listed below. Links to the complete agendas and registration information for each conference are located on the Crop Sciences Research and Education Center web page here.

 

January 22-23: Mt. Vernon – Krieger/Holiday Inn Convention Center. For more information, contact Robert Bellm, (618-427-3349); rcbellm@illinois.edu . Register online at http://extension.illinois.edu/go/icmcmtvernon

January 29-30: Springfield – Northfield Inn Conference Center. For more information, contact Robert Bellm, (618-427-3349); rcbellm@illinois.edu . Register online at http://extension.illinois.edu/go/icmcspringfield

February 6:  Champaign – i-Hotel and Conference Center. For more information, contact Dennis Bowman, 217-244-0851); ndbowman@illinois.edu . Register online at http://extension.illinois.edu/go/icmcchampaign

February 12-13: Malta – Kishwaukee College Conference Center. For more information, contact Russ Higgins (815-274-1343); rahiggin@illinois.edu . Register online at http://extension.illinois.edu/go/icmcmalta


Issues with Nitrogen Fertilizer: Fall 2013

With 85 percent of soybean and 74 percent of corn acres harvested by October 27, the annual process of deciding when and how to supply nitrogen fertilizer for the 2014 corn crop is underway.

Lessons from this past year

Following the very dry first half of 2012 and low corn yields, soil sampling last fall revealed an average of about 80 lb N present as nitrate in the top foot of soil in Illinois. With a lot of rain in late winter and early spring, soil N levels by spring had dropped considerably. And early spring application in 2013 was often followed by a lot of rain before the crop started to take up much N.

The 2013 season was wet early then dry late, but with good root systems that took up water and nutrients well to produce good yields. So far overall N loss this past season does not seem to have been greater than normal. Evidence to support this comes from N trial data just coming in. In an on-farm study coordinated in Champaign County by Dan Schaefer of C-BMP, corn responded almost exactly the same, and with the same yield levels, to fall-applied NH3 as to UAN sidedressed in June. In a study with continuous corn at Perry, sampling in June showed that most of the N applied as UAN in April was still present after more than 12 inches of rain, and yields barely increased going from 180 to 240 lb N, at a yield level of about 200 bushels per acre. At Monmouth, supplementing 165 lb of N as UAN applied in early April with 60 more lb of N in early June, after some 18 inches of rain, did not significantly increase yield of about 240 bushels per acre.

High corn yields mean that large amounts of N were taken up. In the 2013 UI corn hybrid trials, the average yield among the three sites where we measure grain protein was 228 bushels per acre, and the average protein content (at 15% moisture) was 8.4 percent. That calculates to removal of 0.74 lb N per bushel, or 169 lb N per acre. We typically estimate that 2/3rds of the N in the plant at maturity is in the grain; that would calculate N uptake at more than 250 lb N/acre. When we can get 250-bushel yields with 180 lb of N as we did in some cases in 2013, it’s clear that the soil supplied a great deal of N to the crop.

It does not appear that much of the “extra” N needed for the high corn yields in 2013 came from N that was left over after the drought of 2012. As is typical, soybean fields had very low amounts of soil N after harvest in 2012, yet corn following soybeans is – again, as usual – showing less response to N rates than corn following corn in 2013. What data I have so far indicates that corn following corn may not be taking a big yield hit like we’ve seen in some areas in recent years. It’s possible that some of this is because of leftover N, but corn following corn is also showing a typical response to N rate, so it’s not clear that leftover N was a major contributor.

With the weather dry over much of Illinois since August (until rainfall this week), can we expect soil N levels to be high again this fall? I’ve seen numbers from only a few soil samples so far this fall, and they seem mixed, but generally lower than we saw in fall 2012. The crop clearly had the root system to tap into water that was deep in the soil in order to produce the yields that it did, and it’s likely that it brought a considerable amount of N up along with this water. We might expect that this meant removal of much of the N mineralized from soil organic matter, but with some rain now and soil temperatures still in the 50s, there is still some mineralization going on, at least for a few more weeks. But in general, we expect soil N levels to be more or less this fall; we have typically measured only 20 or 30 lb per acre of nitrate-N in the top foot, or even less.

Fall Nitrogen?

The big question that many people have is whether or not to apply N fertilizer this fall or to wait until next spring. We know from nitrate levels in rivers that an appreciable amount of the N present last fall left fields through tiles lines last spring. Fall-applied N generally went out late enough last fall, and soils turned cold and stayed cold after application, so most of the N lost in tile lines last spring came from leftover N rather than from N fertilizer applied last fall. The fact that we’re seeing similar responses to fall- and spring-applied N would support that most fall-applied N stayed in the soil and available to this year’s crop. We are not seeing the unusually large responses to applied N this year that we would expect to see following high N losses.

The basics of fall N application have not changed: the form should be anhydrous ammonia (NH3); soil temperatures should be at or below 50 degree F at the time of application; using a stabilizer/nitrification will slow the activity of microorganisms that convert ammonium to nitrate (the form that can leach); soils should not be wet or very dry, but should have enough water to allow the ammonia to spread to a diameter of 4 to 6 inches as it is released in the soil; and application depth should be 6 inches or more so the NH3 gas doesn’t escape after application. Fall NH3 application should not be done in southern Illinois due to higher chances of soil warming in the fall and earlier warm-up in the spring, and N losses also go up on poorly-drained soils or very light soils, making fall application more risky.

Except when fall weather is warmer than usual, soil temperatures in Illinois reach the 50-degree mark by about November 1; if they don’t, they are usually on the way down and will reach that level soon. You can see soil temperatures in Illinois at a number of websites; the Illinois State Water Survey site at http://www.isws.illinois.edu/warm/soiltemp.asp gives daily minimum and maximum temperatures at the 4-inch depth under bare soil. Minimum values were below 50 in the northern part of the state on October 30, and maximum values were in the mid- to upper 50s through northern and central Illinois. Keep in mind that there will be some biological activity even at 50 degrees, and any warm spell after application will mean more conversion to nitrate. The goal should be to have soils approach freezing temperatures with as much of the N still in the ammonium form as possible.

It is certainly the case that nitrapyrin or other nitrification inhibitors may not be necessary when soil temperatures are low at the time of application and stay low into the spring. Inhibitors also begin to break down as soils warm in the spring (or get or stay unusually warm in the fall), so that by the time the plants are ready to take up N rapidly, often in early June, much of the N will be in the nitrate form. So what we really hope to get from an investment in an inhibitor is a delay in the conversion to nitrate, so that more of the N is still in the ammonium form as soils warm and water starts to move through the soil, taking nitrate with it. On the other hand, when NH3 is applied late enough, the winter is cold, and the spring is dry, there’s little N loss regardless of N form, and an inhibitor will provide little benefit. This means that using an inhibitor is an approach to managing risk.

Another approach that some take to managing risk of N loss is to apply high N rates in the fall, with or without inhibitor, with the idea that some N loss can happen but that there will still be enough N available the next spring. This can certainly work in terms of having enough N, but it comes at a high environmental cost. Not only do we know that high yields of corn grown in productive soils often do not need the high N rates that some producers apply, we also know that too-high N rates will, sooner or later, mean more loss of N to the environment. While loos to the environment may not seem to be a “real” cost (though the additional N is a real cost), it is a real cost, in terms of things like water treatment to remove nitrate, and in terms of image.

One practice that some have adopted is to apply only part of the N in the fall, with the rest applied the next spring. This approach should reduce the amount of N loss if soil conditions become conducive to loss of fall-applied N. And it provides one of the underappreciated benefits of fall-applied NH3, which is having N dispersed through the soil and easily accessible to the plant in the spring. The drawback is that NH3 application is rather slow and costly compared to most other methods of N application, and so applying lower rates increases the cost per lb of N applied.

I mentioned a few days ago the use of subsurface banding of P and K, accompanied in some cases by placement of NH3 beneath this band in the same operation. Making one trip to apply fertilizer increases efficiency, and as long as soil temperatures are low enough, this can work well. As is the case with banded P and K, there is little evidence that applying NH3 under the P-K band provides a yield advantage over applying dry and N fertilizers separately. There has been some tendency in the past for such “dual placement” operations to start before soils are cool enough for fall N application, which increases N loss potential.

One issue with fall NH3 application in recent years has been whether or if to combine application with tillage. Some have applied N and then tilled, while others have tilled first and then applied (and sometimes tilled again after that). Ammonia is extremely soluble in water, and once dissolved in soil water it converts to ammonium. So if there is a moderate amount of soil moisture present, losses of NH3 should be relatively small, even if soil is tilled. Tillage does form air pockets in the soil, however, and if a marginally dry soil is tilled before NH3 is applied, some NH3 could be released before it can dissolv. This would be noticeable as puffs of “smoke” (actually, water droplets attracted by ammonia) after the applicator, and as the smell of ammonia.

Tilling after application does turn soil up where the sun can warm it, and the warmer temperatures might increase conversion to nitrate. If the soil is dry, tilling after application could also release some NH3 that was not dissolved, especially if the soil dries even more as a result of tillage. It also is probably worth asking as well if soil following NH3 application really needs tillage.

N Rates

One of the advantages of applying less than full rates of N in the fall is that it delays the final rate decision until the spring, allowing us to note loss conditions, planting dates, and other factors that might affect the rate we apply. At the same time, as we have seen this past year, the amount of N loss can be difficult to determine. This means that the tendency to apply some “insurance” N to make sure there’s enough operates in the spring as well as in the (previous) fall. In fact, despite a lot of evidence to the contrary, there’s an abiding thought that bringing out full yield potential for a crop that gets off to a good start in the spring will require more than the usual amount of N. We may have had a little less of this than usual this past spring – with the crop planted as late as it was it didn’t seem to be off to a great start. The fact that we are hearing of some yields above 250 bushels per acre, often coming with “only” normal amounts of N, should help a few more of us to start to question whether high yields only come when we pour on the N.

The N rate calculator located at http://extension.agron.iastate.edu/soilfertility/nrate.aspx remains our best “range-finder” for guiding the process of determining N rates. For central Illinois corn following soybeans, and with NH3 priced at $680/ton ($0.41/lb N) the current guideline rate is 167 lb N/acre (204 lb of NH3), and the range is 154 to 183. In northern Illinois, the most profitable rate under these same prices calculates to 149 lb N/acre, with a range of 137 to 163. As we have noted before, the ratio of N to corn prices tends to stay relatively constant over time, with a bushel of corn equal in value to about 10 lb of N (in the form of NH3). Changes in fertilizer prices by next spring are likely not to greatly change the guideline rates, but of course adjustments in total N applied can be made in the spring.

Cover crops and N?

Cover crop seed has been dropped or drilled into a lot of Illinois fields this fall. Ongoing dry weather has meant delays in germination in many areas, and temperatures down into the low 20s last week might have damaged some small cover crop plants, especially in harvested fields with cover crop plants more exposed. Growth of the cover crops will hopefully pick up now, but delays at the start may mean less growth before cold weather sets in.

We expect that a cover crop with vigorous growth and a good root system will take up some N left in the soil in the fall, and more N next spring if the cover crop overwinters. Once taken up into cover crop biomass, N is less likely to be lost to tile lines. From a crop standpoint, the N in the cover crop will be of value only if the next crop is one like corn that requires N from outside sources. The breakdown and release of cover crop N and its supply to the next crop is a biological process that depends on the weather. Cover crop residue in the spring can also affect soil temperature and water content, and so can affect the planted crop in ways other than through N supply.

One idea that has been floated is that fall cover crops can help take up fall-applied N, thus keeping it safe from loss and preserving it until the corn crop is up and growing next spring. This may happen to some extent, but fall uptake will usually be limited if the cover crop starts to grow well only after harvest of the crop it’s planted into, and if fall N is applied only after soil temperatures reach 50 degrees; this will typically give only a few weeks of uptake, or even less. Applying NH3 into growing cover crops will cause some damage to roots, and when soil temperatures are cool and dropping, it’s not likely that such roots will be able to take up much of the fertilizer N up before soil temperatures get low enough to halt root activity.

Uptake of fall-applied N increases as soils warm in the spring, but vigorous cover crops like cereal rye need to be killed in March, and soil temperatures by that time are usually still cool. As an example, average soil temperature at the 4-inch depth reached 61 degrees near Champaign in mid-March of 2012, one of the warmest Marches on record, but reached only 46 degrees by the end of March in 2013 and did not reach 60 this year until the end of April. So while we think that cover crops can have beneficial effects on N nutrition, we don’t expect this to be consistent over years. We certainly cannot afford to get sloppy with fall N thinking that cover crops will bail us out to prevent loss.

 


Fall Fertilization for the 2014 Crop

Corn and soybean harvest continues to move along in Illinois, and as the 2013 crops come off, thoughts turn to fall fertilization. In this article we’ll discuss nutrients other than nitrogen. This will be followed soon by an article on nitrogen.

P and K

In areas with dry soils, we have in recent years had reports of lower than expected soil test K values. There might be some of this in 2013, but we’re also hearing some reports of soil test P and K levels higher than expected. Test levels lower or higher than previous test levels, additions, and removals would suggest are not uncommon, and reasons for this are not always clear. Unusually low soil test levels need not be taken as a sure indicator of deficiency; neither should high tests be taken as an indication that nutrients are not needed. As long as previous soil tests were not low, and nutrients removed in harvested crops are being replaced with fertilizer additions, crops should be getting the nutrients they need.

Some questions have been raised about whether the “book” values for P and K grain concentrations, used to calculate removal, are still accurate. Dr. Fabian Fernandez, now at the University of Minnesota, produced data from Illinois grain samples (taken mostly in 2009) showing average P and K concentrations in corn grain of only 0.27 and 0.19 lb per bushel, compared to the book values (from the Illinois Agronomy Handbook) of 0.43 lb P and 0.27 lb K per bushel. Soybean values were closer to book values, at 0.69 (new) compared to 0.83 (old) lb P and 1.17 (new) compared to 1.30 (old) lb K per bushel. Other states also have some data showing lower values than the ones commonly used.

It’s certainly possible that higher yields and different genetics over the decades since these book values were produced might have lowered these values. But until we have more data to confirm this, it seems prudent not to lower removal/replacement amounts by a lot. Let’s consider an example in which soybeans in 2012 yielded 45 bushels per acre and corn in 2013 yielded 180 bushels per acre. This would produce 2-year P removal totals of 115 lb P per acre under the old (book) values, and only 80 lb P per acre using the new values. Using the old values would calculate removal of 107 lb K per acre, and the new values would calculate to 87 lb K removed per acre.

A reasonable approach might be to split the difference, calculating replacement as the average of the old and new removal amounts. In this example, that would mean replacing (115 + 80)/2 = 98 lb P and (107 + 87)/2 = 97 lb K per acre. An exception to this might be where P and K test levels are likely to be on the low side, in which case we might want to base replacement on the old book values to minimize the chances of deficiency.

Materials and placement

Most P goes on as ammoniated phosphates MAP or DAP, but forms such as DAP manufactured to include other nutrients such as sulfur and zinc are also marketed. We have not seen much response to additions of S, Zn, or other micronutrients in Illinois field crops, but can’t rule out possible responses. Micronutrients such as manganese, iron, and zinc are required in small amounts and can be partially immobilized if they are applied long before crop uptake begins, so are often applied in the spring; applying these in the fall can probably work if rates are adequate. Sulfate can leach much like nitrate, so elemental S, which is gradually converted to sulfate in the soil, is a safer form of S for fall application than is sulfate.

Another practice that is growing some in Illinois is placement of P and K in subsurface bands, usually 4 or 5 inches deep. Some may call this strip-tillage, though much strip-tilling is done without fertilizer placement. Strip-tillage usually includes planting on top of tilled strips in the spring, a practice that is not always followed with nutrient banding. In some cases fields are tilled after banding, probably shallow enough not to disturb the band, and rows might or might not be on top of the bands. Banding P and K can also be coupled with NH3 application in the fall, with the NH3 knives usually running a few inches deeper than the dry fertilizer band. Equipment to do this was much in evidence at the Farm Progress Show this year.

The equipment expense, power requirement, and relatively slow speed of application compared to broadcast fertilizer make banding fertilizer more expensive than broadcast. This means that banding needs to increase yields or lower fertilizer costs in order to make it pay. There has been a fair amount of research done on this, and most has shown little effect of this practice on yield, compared to broadcast-applying the same fertilizer rate and form. When crops are planted over the band, roots of the crop reach the band of fertilizer quickly, and the crop can take up most of the P and K it needs from the band. But roots have to go out into the bulk soil to take up water, and there is no advantage to having the plant take up most of its P and K in only the small part of the root system – the roots in the band – rather than throughout the root system.

In soil with very low soil test levels, roots in the bulk soil might not encounter high enough P and K levels, in which case either band placement or broadcast fertilizer should help. Without tillage, broadcast fertilizer nutrients will take more time to get into the root zone than if nutrients are banded. Finally, in soils with a tendency to tie up nutrients, banding can increase availability compared to dispersing the nutrients throughout the soil. These factors are of limited importance in Illinois soils with medium or higher soil test levels of P and K – in other words, in soils where P and K are seldom limiting to yield.

As a final point, remember that banding is a tillage operation, and that there could be a tillage effect separate from the effect of fertilizer placement in such systems. Of course, one trip to till and apply fertilizer is efficient, but strip-till by itself is less costly and usually faster than is band-placing fertilizer.

Lime and gypsum

Lime corrects low pH in soil, and with dry soils and with time for the lime to react in the soil to raise pH before spring, fall is the best time to apply it. We don’t see much indication that more expensive forms of lime, such as that shipped from a distance to better balance calcium and magnesium in a soil, provide much return to what is typically their higher cost.

In some parts of Illinois, usually those within reasonable shipping distance of a coal-fired power plant, gypsum is actively marketed as a soil amendment. Calcium carbonate (lime) or material derived from lime is used to remove sulfur from flue gas, resulting in formation of calcium sulfate, or gypsum. Such scrubbing is required, and coal-fired plants produce large amounts of gypsum. This gypsum represents a disposal challenge for power plant operators, and finding uses for it has been an ongoing process. Some gypsum is used to produce wallboard and other products, but gypsum continues to accumulate, and in some cases is being stored in landfills.

The two major selling points for gypsum use as a soil amendment are that it can serve as a source of sulfur, and that calcium ions can help bind soil particles together, which can help improve soil structure. Some also promote gypsum as a calcium fertilizer, but we have no good evidence that, given the large amount of exchangeable Ca in Illinois soils (some natural, some from lime application) and low requirements of our field crops for Ca, there is any need for Ca fertilizer. We also don’t have much evidence that S deficiency is widespread in Illinois, but applying gypsum will certainly provide S to a crop that follows. The S in gypsum is in sulfate form so can be leached through the soil, but quantities of gypsum typically applied are large enough that any crop S requirement will still be met.

Use of gypsum as a way to improve soil structure and drainage has been promoted fairly heavily in recent years. The basis for this is that Ca in soil solution exists as a divalent cation, with two (positive) charges. Clay and organic matter surfaces are negatively charged, so Ca ions act as a sort of “glue” to hold these particles together, making soil structure more granular and improving tilth, aeration, and water movement. In soils with a lot of sodium, including the “slick spots” common in some parts of Illinois, Ca ions will, if added in large quantities and given time, replace some of the sodium ions and improve permeability and soil productivity.

The real question regarding addition of large amounts of gypsum to improve soil productivity is whether the improvement is enough to pay the cost. Soils of medium or heavy texture already contain a great deal of Ca, and adding a few hundred or even a thousand or more pounds of Ca in the form of gypsum (or lime) may not produce much noticeable effect. High-clay soils, often targeted for marketing of gypsum due to their perceived poor structure, would require a great deal of gypsum (Ca) to produce an effect. So while adding gypsum to soil may have some effect, it is not at all clear that productive silt loam or silty clay loam soils with adequate (tile) drainage and with pH maintained by adding lime will be noticeably improved by this addition.

Perhaps because both contain calcium, there continues to be some thought that, like lime, gypsum will raise pH when applied to soil. But it is the carbonate in lime that provides the neutralizing effect, and straight gypsum has no carbonate, so does not affect soil pH. Scrubbers in some older power plants might produce gypsum that contains some lime, but neutralizing ability of such material would need to be confirmed by testing, and in many cases is probably negligible.