Nitrogen in Late Spring 2014

The corn crop in Illinois is off to a good start in many fields, and in most areas is in the V5 to V8 growth stages, just starting its rapid growth phase. On average, the crop under good conditions will add some 200 lb of dry matter per acre per day over the next 80 days or so. It will take up 3-4 lb per day of nitrogen before pollination, after which the N uptake rate will slow.

The spring of 2014 has not been a wet one overall in Illinois. But as usual, rainfall has been very unevenly distributed; some areas have received 6 inches or more over the past month. In the wetter areas, getting sidedressed N applied has been challenging, and some who applied the full amount of N are concerned about how much might have been lost.

Low temperatures through the winter and into early April helped preserve fall-applied N and the small amount of residual N left after last year’s big crop. April and May temperatures were normal to a little above normal. Maximum soil temperatures 4 inches deep under bare ground reached the mid-70s by mid-May, and into the 80s during the warm periods in late May and early June.

Soil temperatures in the 70s and 80s increase activity of soil microbes, both those responsible for mineralization (release of plant-available N from soil organic matter) and those that convert ammonium (NH4+) to nitrate (NO3). Table 1 has results from six Illinois fields sampled for N in May by Dan Schaefer of the Illinois Council for Best Management Practices (C-BMP) under the N-Watch® program. These results confirm that N loss was not been excessive by mid-May, and also that much of the fall-applied N was in the nitrate form by May. The fact that more N was recovered than had been applied is not unusual; mineralization and carryover N contribute to the amount that’s there.

Table 1. Amounts of N recovered from Illinois fields following application of a variety of N forms, rates, and timings. Sampling took place in early to mid-May 2014. Data from Dan Schaefer.

While many soils are moist or even wet, the threat of N loss is far higher where water has stood, or is standing, than where water didn’t stand for more than an hour or two. The heavy downpour that brought 3+ inches of rain to parts east central Illinois on May 21 left a lot of standing water, but by 12 hours later, much of it had run off the fields. This indicates two things: 1) rainfall rate exceeded the infiltration rate, so less water entered the soil than fell on the soil in most places of many fields; and 2) standing water affected a relatively small percentage of the soil surface.

Where water stands long enough – typically 3 to 4 days at warm temperatures – for the crop to begin to lose some of its green color, that’s a signal that soil oxygen is becoming depleted. Two negative consequences of lack of oxygen are: 1) the start of denitrification (conversion of nitrate to gaseous forms of N) and N loss; and 2) the beginning of root damage, some of which may be permanent. Most of those fields have recovered well.

We can assume that most fertilizer N is by now in the nitrate form, though some of that applied as sidedressed NH3 or (to a lesser extent) as sidedressed UAN may still remain as ammonium. This is typical for mid-June, and it means that the N is subject to denitrification and, in lighter-textured or tile-drained soils, to moving out of the rooting zone.

Measuring N loss from wet soils is not very practical, especially while it’s still wet. Previous work has shown that, at soil temperatures in the 70s, as much as 7 or 8 percent of the nitrate present can be converted to gas and be lost for each day the saturated conditions persist. Conversion rates may be lower than this with lower temperatures deeper in the soil and at night, if some of the N is still in the ammonium form, and if soils still have some oxygen present. So denitrification losses may be less than expected in some fields. And if plants are badly damaged by saturated soils, loss of N may be a smaller problem than the loss of yield potential from plant damage.

It’s rare that whole fields remain saturated for days, so in most fields, the risk of N loss by leaching or through movement out of the field through field tiles is greater than the risk of loss by denitrification. Tiles began running relatively late this spring, which helped keep N in the fields. The first water to reach the tiles came, in many fields, from rainfall before the N was all converted to nitrate, or from before N had been applied, so may have carried relatively little nitrate. But by June, it’s not unusual for water from field tiles to have nitrate-N levels of 10 to 20 parts per million. At 15 ppm N, one acre-inch of water leaving the field carries with it about 3.8 lb of N.

In fields where all of the N has been applied (especially if some was applied in the spring as NH3), where crop color has remained or returned to healthy green, and where there is no standing water now, it’s reasonable to assume that it’s not necessary to add more N. In fields where all of the N has been applied but where water stood long enough to have the crop lose much of its green color, adding supplemental N will increase yield only if plants can grow enough new roots to take advantage of the added N. Chances of such recovery are much greater when the water comes in early vegetative growth like it did this spring (so far, at least) than when it comes later.

In fields that still need sidedressed N, or where plants stood in water to the point of turning pale green but now seem to be recovering, N should be added as soon as practicable. The easiest way to apply N to wet fields is as urea (with a urease inhibitor such as Agrotain® added) applied by air, but that’s also costly. Waiting until high-clearance equipment can get through to apply broadcast urea with urease inhibitor or UAN (also with urease inhibitor, especially if rainfall is likely to be delayed) using drop tubes is usually cheaper, but may require days or weeks to dry out enough.

The amount of supplemental N – that applied to make up expected loss after a full rate was applied – should generally not exceed 50 lb of N or so. If a planned sidedress application is made late, plant uptake will start quickly, reducing the time available for loss. That may allow the rate to be lowered from what had been planned, especially if the planned rate would have brought total N to the higher side of guideline rates.

While it’s good to apply supplemental N (if it’s needed) or planned sidedressed N as soon as we can, the yield cost of further delays depend on the N available to the plant now. The best way to know how much N is available to the crop now is to observe canopy color; as long as leaves remain a reasonable shade of green, the plant is not deficient, or not deficient enough to cost yield as long as final N supply is adequate. In that case, some delay in applying N may not cost any yield. If it turns dry after surface application of N, uptake will be delayed and the risk will increase of having the crop run out of N.

Putting all this in perspective, the 2104 season has not been one of above-average N loss potential, except in areas that were unlucky enough to get big downpours. Remember that mineralization of soil organic matter is contributing substantially to the N supply in the soil now, helping to counter some N loss from tile lines. This is not the case in saturated soils, where mineralization is slowed as denitrification speeds up.

Still, if good rainfall and temperatures continue, the N supply, even if it’s reduced some by loss, is unlikely to limit yield. In fact, most of the highest yields we have seen in several hundred N rate trials over the last 20 years have come at modest N rates. I think this happens because good root systems mean good uptake of water and N, and that conditions that are ideal for yield also tend to be very good for soil N supply.


Another Look at Soybean Planting Date

Soybean planting is off to a mediocre start in Illinois, with 26% of the crop planted by May 11, and limited progress with the rain of this past week. Planting will resume in some places this week, but other areas remain wet and it will take some time for soils to dry out. In comparison with recent history this is not yet a serious delay, but as time passes the delay will become a bigger concern.

Over the past four years we have conducted studies that, among other things, have compared yields of soybeans planted over a range of dates, from mid-or late April (or when conditions allow) into early to mid-June. This research was funded by the Illinois Soybean Association.

We were unable to produce useful data from most southern Illinois sites due to the late start in many cases, and poor stands in others. This demonstrates little other than that late starts are quite common in southern Illinois, and that poor stands are not more common from early planting than from late planting. Instead, poor stands almost always result from heavy rainfall soon after planting, regardless of when the crop is planted.

I combined data from 15 site-years (not including Perry in 2012, where yields were every low) in central and northern Illinois, with yields at each site-year calculated as percent of the maximum yield for that trial. Figure 1 shows the overall response to planting dates over these sites. The average maximum yield across all trials was 66.2 bushels per acre, so each percentage point is about 3/2rds of a bushel.

Figure 1. Response of soybean yield to planting date over 15 Illinois site-years, 2010-2013.

Based on these numbers, a delay to May 20 means yields on average about 10% less than maximum. From May 20 to the end of May, the drop is about 0.5 % per day of delay. From June 1 to 10, it is about 0.6 % per day. The cumulative loss by June 10 is about 20%.

While Figure 1 shows the best prediction we have for planting date in Illinois, the curve doesn’t tell the whole story. When we look at yield data from separate trials, we find that there seem to be two lines – one for trials where yields are high and one for trials where yields are lower (Figure 2).

Figure 2. Soybean yield response to planting date over 15 Illinois site-years, divided into higher- and lower-yielding sites.

Because we typically don’t know what yield level will be, data presented as in Figure 2 don’t provide a better prediction of yield loss than Figure 1. Rather, they simply show that when something other than planting date limits yield, planting date becomes less important as a factor that influences yield.

As I said about corn planting date in an earlier article, having planting delayed by wet weather past a certain date – May 15 or 20 for soybeans – does not rule out getting high yields. But we still want to plant as soon as we can in order to have plants take better advantage of growing conditions that should continue to improve starting soon.


Considerations for fungicide management of Fusarium head blight of wheat

Wheat plants are now beginning to head out and flower in parts of southern Illinois. During this critical time of wheat development, wheat becomes susceptible to infection by Fusarium graminearum, the causal agent of Fusarium head blight (FHB; also known as scab) (Fig. 1). This disease can cause reduced grain yield, test weight, and quality. In addition, the fungus can produce toxins that will contaminate grain such as deoxynivalenol (DON; also known as vomitoxin). Harvested grain with high levels of DON may be discounted or outright rejected at the elevator. To achieve the best management of FHB, different management practices must be implemented, such as planting wheat into fields that were previously cropped to soybean (rather than corn), planting wheat varieties with moderate to high levels of resistance to FHB, and applying foliar fungicides at the proper timing. Of these different management practices, the application of foliar fungicides is the only one that can be done during the growing season and is the main focus of this article.

Fig. 1. Symptoms of Fusarium head blight (scab) of wheat (note the “bleached” heads).

Multiple fungicides are registered for use on wheat, but only a few have efficacy in managing FHB. Fungicides available for FHB management all belong to the triazole class of fungicides and are Caramba (BASF Corporation), Prosaro (Bayer CropScience), Proline (Bayer CropScience), and products that contain tebuconazole as their solo active ingredient. Of these products, the best efficacy has been obtained with Prosaro and Caramba in multi-state university field research trials. Proper fungicide application timing is critical in achieving the best efficacy. The best application timing is considered to be when plants are beginning to flower (early anthesis – Feekes growth stage 10.5.1), but some efficacy may still be achieved slightly before or after Feekes 10.5.1 (Table 1). In regards to fungicide application timing, it is important to always follow the label recommendations and consider the preharvest interval (PHI) requirements (PHI for Caramba, Prosaro, Proline, and tebuconazole products is 30 days). Fungicide products that contain strobilurin active ingredients should not be applied for control of FHB, and most do not list FHB control or suppression on their label. In multiple university research trials, strobilurin fungicides have been shown to increase DON levels in grain compared to non-treated checks. Therefore, it is extremely important that only effective triazole fungicides be applied for management of FHB.

Table 1. Effect of fungicide application timing on Fusarium head blight (FHB) control in wheat. Results represent data collected from Dixon Springs, IL in 2009, and Brownstown, IL, Carbondale, IL, Dixon Springs, IL, and Urbana, IL in 2010.

Fungicide

Application timing

FHB (% control)*

Prosaro @ 6.5 fl oz

Feekes 10.5

35 b

Feekes 10.5.1

59 a

5 days after Feekes 10.5.1

37 b

Caramba @ 13.5 fl oz

Feekes 10.5

38 b

Feekes 10.5.1

61 a

5 days after Feekes 10.5.1

36 b

*Values followed by the same letter in the table are not significantly different with 95% confidence.

When making a decision on if a fungicide application is needed, FHB risk should be assessed. A FHB Prediction Tool is available on-line at www.wheatscab.psu.edu. This risk is based on weather conducive for FHB, and should be assessed for each field as they begin to develop heads in anticipation of flowering. On May 9, 2014, a LOW risk of FHB was present in all of Illinois; however, this status can and will change depending on weather conditions. Therefore it is important to continually monitoring the FHB Risk Prediction Tool as more and more wheat fields get closer to the flowering stage.


Another Look at Corn Planting Date Response

As we head into May, Illinois is ahead of most of the rest of the Corn Belt, with 32% of the corn crop planted here by April 27, close to the 33% that was planted by that date averaged over the past 5 years. Only 19% of the US corn crop was planted by April 27, and states to the north and east of Illinois were in single digits. It is wet in much of the Corn Belt now, and further delays are expected.

We’ve been running planting date studies for a number of years at a number of sites in Illinois. While there’s always a lot of variability in planting date responses, we do have data sets that combine well – where there is some consistency over years and where yield levels were not wildly variable. One such set is from DeKalb and Monmouth over the past seven years – 2007 to 2013 (Figure 1). Data from several years at these sites were used to develop the corn replant model in the current Illinois Agronomy Handbook. These sites also represent the Corn Belt quite well, so results are applicable over a wide area.

Figure 1. Response to planting date combined over seven years (2007-2013) and two sites in northern Illinois.

Combining data by percentage of maximum yield for each site and year shows that highest yield comes at about April 20 (Figure 1). This is similar to what we’ve seen as the “best” planting date in most recent planting date summaries. But yield penalties from planting delays are somewhat milder here than we have previously reported. Compared to the highest yield (on April 21), the yield loss for planning on April 30 was 1% (2 bushels); by May 10 it was 4% (8 bushels); by May 20 it was 8% (17 bushels); by May 30 it was 14% (29 bushels); and by June 10 the total yield loss predicted from these data was 22%, or 49 bushels per acre.

The average maximum yield across all sites was 216 bushels per acre. Losses measured as bushels per acre per day of delay, for 10-day periods starting on May 1 were:  May 1-10 (0.6 bu/acre/day); May 10-20 (0.9); May 20-30 (1.2); and May 30 to June 10 (1.9). Thus the loss accelerates, with more loss per day of delay the later it gets. Because average temperatures rise during April and May, the per-GDD yield loss would accelerate less than the per-day loss – it would be closer to a straight line.

These results bring up an obvious question: has the planting date response really changed, or are we just looking at a “favorable” set of data? That’s not completely clear, but I do think that increasing tolerance to the stress of high populations has likely helped plants to also do better under increased weather-related stresses, especially during pollination, that are more likely with late-planted corn than when the crop is planted early. Seven years is a reasonable “sample” of years, and these results weren’t only the product of what happened in one or two “odd” seasons.

One lesson we certainly can take from this is that having planting delayed to early or mid-May does not mean “game over” in terms of yield potential. Average GDD accumulations during April range from less than 200 in northern Illinois to about 300 in southern Illinois, and amount to less than 10% of the seasonal total. In other words, losing April doesn’t greatly diminish how much season is available to produce a crop. The main reason why late planting lowers yield is due to the increased chance of water stress when pollination is delayed.

The April 1-planted corn in our planting date study here at Urbana is at the 1-leaf stage now, and not looking great with night temperatures around 40 and daytime highs in the 50s this week. Plots planted on April 1 at Perry froze before emergence, and will have to be replanted. So this year, early planting didn’t get the crop very far ahead.

Our hope now is that temperatures will start to rise and will remain at least as high as average through May. This will help both to dry the soil after rain and the crop to take off once we get it planted. But as much as we hope we can finish planting within the next couple of weeks, rain in July will, as usual, be the main thing we’re going to need for good yields in 2014.


Running On-Farm Strip Trials

On April 16 I posted an article http://bulletin.ipm.illinois.edu/?p=1966 on the use of nitrogen fertilizer on soybean, mentioning at the end of the article that this would be a good thing to test in on-farm trials. Here I’ll provide a little background and a brief description of how to go about doing such a trial.

Background: dealing with variability

If there were no variability in yields (or soils) going across a field, a single strip of N fertilizer (or without N while applying N to the rest of the field) would measure the effect. There is no such field: every strip will yield at least a little more or less than every other strip in every field. So a single strip where we might plan to apply N fertilizer will always yield differently than the strip next to it, and we can never be sure if any “difference” we see in yield was due to treatment or just to this “random” variability, with one or another treatment just “lucky” in getting assigned by chance to higher-yielding strips.

One way we deal with this variability is to locate trials in the most uniform part of the field we can find. This can never eliminate variability between strips, but it minimizes it. Using a yield map from a previous year can help find areas in the field where there is good uniformity. If a map of a given field doesn’t show an area large enough for a trial with good uniformity, consider moving the trial to a different field. If strips need to be shorter than the field in order to avoid a variable area, it’s OK to do that, as long as good yield measurements are possible.

The only way we can measure and deal with the strip-to-strip variability in a field is to replicate treatments – that is, to apply the same treatments to a number of different strips. The variability among yields of strips treated the same tells us how variable yields are, and we then use stats to help us figure out if yield differences between treated and untreated strips are probably due to treatment or could easily be due to random variability and chance placement of treatments.

If we can’t be sure that a difference is due to treatment and not just to random variability, then we have to conclude that we haven’t proven that the difference is due to treatment, and we say the difference is “not significant.” This doesn’t mean the treatment did nothing, it just means that we haven’t proven to our satisfaction (that is, to a probability level of 90 or 95%) that it did. By the same token, a treatment that does nothing at all can get “lucky” and end up on higher-yielding strips by chance, producing a “significant” difference that was really no difference at all.

Running a strip trial

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

  1. Find a uniform part of a field large enough to accommodate 12 strips wide enough to apply N fertilizer to, and large enough to get accurate harvest yields with the combine. Unless N can be dropped very precisely to strips exactly as wide as the combine will harvest, N strips will need to be wider than the combine. They should be long enough to get a good yield estimate, whether that’s with a yield monitor or a weigh wagon. Record GPS coordinates for the 4 corners of the area, soil type, previous crop and its yield, planting date, seeding rate, variety, herbicides, application date, harvest date, and anything else that you think might have affected the crop.
  2. Assign treatments to strips randomly within each pair of strips. Here is how this might look:
  3. Strip 1 No N
    Strip 2 +N
    Strip 3 +N
    Strip 4 No N
    Strip 5 +N
    Strip 6 No N
    Strip 7 No N
    Strip 8 +N
    Strip 9 No N
    Strip 10 +N
    Strip 11 +N
    Strip 12 No N
  4. Apply in-season N to the strips where it was assigned. Timing and form are not fixed, but I suggest using 50 to 80 lb of actual N (120 to 200 lb urea 45-0-0 or similar; protecting with a urease inhibitor and using slow-release urea in the mix are good options) applied between stage R4 (full flower) and R6 (full seed). Liquid (UAN) can be injected, but dry forms are most common and easiest to apply in plants this size. If you drive down strips to apply by ground, and there’s a possibility that this will do some damage, you’ll want to drive (with applicator off) down the “No N” strips as well so all strips experience the same thing. N can be applied by air, but strips will need to be wide enough so fertilizer doesn’t fall into no-N strips. Make certain, either with GPS or with flags (PVC lengths installed using a soil probe work well and are visible), that you know exactly where the N went on and where it didn’t, so you can harvest correctly.
  5. Harvest and record yields for each strip. Be sure that the width harvested is the same for each strip, and trim the ends if using yield monitor data.
  6. Average yields with and without N to see if there are differences. Do a statistical analysis, or work with an adviser to do so. If you wish, you can send me yields on a spreadsheet and I’ll return it with stats run and a note about the outcome. If you do your own analysis, I’d much appreciate getting the data so we can look at this across all sites.

Doing such trials in different soil types – especially in soils with different textures and amounts of organic matter – will help show whether or not an N response is affected by soil. Some may want to do trials in more than one field, or to cooperate with neighbors to do this. For questions like this, the more data, the better.


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.