Is This Corn Really Sulfur Deficient?

by Daniel Hudson, UVM Extension Agronomist

A farmer called several weeks ago and said that his corn was looking ‘striped.’ The interveinal chlorosisagronomic jargon for this condition is ‘interveinal chlorosis.’ Indeed, it was faintly, yet distinctly exhibiting those symptoms.
His theory was that it was sulfur or magnesium deficiency, which was a very reasonable starting point. Most farmers are somewhat familiar with various nutrient deficiency symptoms in corn:

  • Purple corn on cool soils usually indicates phosphorus deficiency (which is often temporary)
  • Yellowing and tissue death on leaf margins, beginning with lower leaves? Potassium deficiency!
  • Generally yellow and spindly plants; yellowing of leaves starting at the bottom and moving upward with time; yellowing begins along midrib and moves outward toward the margins; lower leaves and previously yellow tissue often in various stages of death: nitrogen deficiency!
nitrogen deficiency in corn

symptoms of nitrogen deficiency

In this field, however, the lower leaves were deep green, and the upper leaves tended to be more  striped. Looking at an individual plant, the symptoms were similar to sulfur deficiency, but basically every plant in the field had the same symptoms — there were no patches where the corn looked ‘normal.’

Ordinarily, I would expect a sulfur deficiency to be on sandy soil and to be patchy/localized.  Because manure application is never perfect, the corn in areas where manure was applied more heavily are much less likely to have the symptoms. However, nobody had seen/noticed a sulfur deficiency on this field before, it receives manure (a good source of sulfur) and the soils were warm (which often increases sulfur availability and IMG_2696results in sulfur deficiency symptoms disappearing). Together these things were pointing to hybrid (genetics) interacting with environmental effects without a clear connection to a particular nutrient deficiency.

When in doubt, taking a tissue test can reveal the nutrient deficiency that is responsible for the deficiency. Ideally, a separate composite sample will also be collected from asymptomatic plants in the same field and of the same variety, but in this case there were no asymptomatic plants. Given the stage of maturity, rather than collecting whole plants or ear leaves, we collected 20 youngest fully developed leaves from around the field. The leaves were submitted to Cumberland Valley Analytical Laboratory via the feed company. The analysis showed that while boron, manganese, and magnesium were on the lower range of the sufficiency range, the symptoms were not consistent with deficiencies of any of those nutrients. Sulfur (the primary suspect) concentration was toward the middle of the sufficiency range, and the mild interveinal chlorosisN:S was about 14:1, which is not problematic. One caveat I will add is that there is an interesting theory floating around that with the yield potential of modern corn hybrids, the ‘sufficiency range’ should be indexed to yield potential, i.e., the sufficiency range for corn grown in a context where it is headed for 17 tons/acre will be different from corn at the same developmental stage that is headed for 30 tons/acre. That said, published sufficiency ranges might not be nuanced enough and may need refining.

The aforementioned farmer had the same hybrid planted in another field located 30 minutes from the home farm, and the plants in that field exhibited the same symptoms.  At this point everything is pointing toward variety X environmental effects. Since then, I have seen a couple of other farms with similar symptoms in their fields.

Internet searches will reveal various articles discussing plants with symptoms discussed above.   Richard Taylor (University of Delaware) has observed the phenomenon in Delaware and Greg Binford (Wilbur-Ellis, formerly at University of Delaware) apparently have observed similar things in the Midwest. While they lean toward a sulfur-involved hypothesis, they believe that there is a varietal aspect, yet acknowledging that grain yields from fields with ‘symptoms’ can still exceed 300 bushels/acre (which is phenomenal). At the same time, intuitively, yellow stripes suggest less chlorophyll, which makes one wonder about less photosynthesis and compromised yield.

What to do?? Take a look at your fields and let me know if you see these symptoms in any of your fields. If you do, please let me know which varieties are exhibiting the symptoms. Maybe we can find a pattern and better understand what is going on, whether it is a concern, and how to deal with it. Contact: mobile: 802-535-7922.

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Alfalfa and tall fescue: what you should expect from them and what they expect from you

A refresher on profitable management of alfalfa and tall fescue.  Click the picture to go to the article located at the Progressive Forage website.

alfalfa and tall fescue pfg


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What do you know about meadow fescue?

Here is an article that I recently wrote for Progressive Forage on the subject of meadow fescue — a grass that deserves serious consideration by those interested in forage quality.  Click on the picture below to go to the article.


pfg meadow fescue pic

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Unlocking Your Corn Sidedress-Nitrogen Recommendation

There is a certain precise amount of nitrogen that your corn crop will need this year in order to achieve its yield potential.  The problem is that nobody knows what it is.  Another problem is that nobody can afford to guess.  Money is too tight to just throw extra nitrogen on the field, and inventory is too important to go the route of allowing your sidedress rate correlate with the milk price.  The good news is that there are good tools for figuring out what your sidedress rate should be!

Adapt-N and the PSNT are useful tools for predicting sidedress nitrogen needs for corn.  IMG_1390

While Adapt-N is a great tool, you need to have a certain set of data to make it work.  The good news is that if you have a current nutrient management plan, you have most of the information you need already!

In order to make the process of transferring that information from the farmer to the program (or the consulting agronomist), I have created a couple of forms that have all or most of the data necessary to make Adapt-N work.  The PDF version of the form will work for those just interested in hand-writing the information.  The Excel version of the form will be more useful for someone with multiple fields or fields with zones where the treatment is similar from one field or zone to another.  For example, if fields 1,2, and 3 all had the same manure rates, hybrids, and planting dates, you could enter all the data that is the same for all of the fields, and then save the document under three different names, and finally enter the correct unique information into each of the respective documents.

The PSNT is a good-old standby that works most of the time.  The problem is that it does not know that we have had a cool spring and that a lot of the nitrogen in the pipeline (i.e., soil organic matter) has not mineralized at the same rate it would have if temperatures were warmer.  It does not know about our weather patterns.  That said, the PSNT will generate a recommendation that is better than blindly guessing.  Keep in mind that the PSNT should be taken only when the corn is 6-12″ tall and that the PSNT is not useful if broadcast applications of nitrogen have already been applied.  Be sure to avoid taking samples near the zone where starter fertilizer was placed.

See also:

Cornell PSNT Fact Sheet

2016 Cropping Season Addendum to Nutrient Recommendations for Field Crops in Vermont

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Why You Should Consider Adaptive Nitrogen Management for Your 2016 Corn Crop

Corn needs nitrogen.  A 20 ton/ac corn crop removes 180 pounds of nitrogen from the soil.  That nitrogen comes from manure, decomposing soil organic matter, fertilizer and a small amount is deposited when it rains.  A certain amount of nitrogen is lost when manure is applied (from ammonia volatilization), and other losses include leaching, IMG_1390denitrification, and fertilizer (urea) volatilization.  In some cases, such as when the cover crop gets too mature, otherwise available nitrogen can become immobilized for more than a year.  With all of these potential losses and other dynamics, how can one predict how much additional nitrogen fertilizer (if any) they will need to reach their corn yield potential?

By now, most of you have probably heard about the Adapt-N tool that Cornell developed several years ago; some may even be tired of hearing about it.  This software is roughly analogous in concept to the ration-balancing software that your dairy nutritionist uses.  In the same way that you don’t use your 2014 forage tests to develop your 2016 rations, the Adapt-N program will only give good information if you feed good and current information into it.  The program needs data for each field including: expected yield, planting date, relative maturity of the hybrid you planted, plant population, manure test information, manure application dates, date of manure incorporation, soil organic matter, GPS location, etc.  This allows the program to model nitrogen behavior in the soil, crop development, nitrogen demands, etc.  It will even give you a ‘virtual pre-sidedress nitrate test (PSNT)’ that you can compare to a physical PSNT if you want to ‘ground-truth’ the program.  It is a TREMENDOUS program.   That said, no approach to N management is perfect.

  • Guessing or just applying the same amount of N every year is a very bad idea.Some years you could run short and lose 30% of your yield.  Other years you will over-apply and have environmental losses and a poor return on your investment.
  • The PSNT can give good information, but between rocks that make sampling frustrating, trying to make hay, heat, labor, and other factors, it rarely gets done and often results in getting the recommendation too late.  While the PSNT can yield a good recommendation and is certainly better than guessing, it is mostly blind to present and past weather conditions and often ends up over-recommending sidedress N.

The pieces of information that farmers often do not have and which often prevent them from being able to use Adapt-N are 1) a  current soil test (to give us the organic matter number), and 2) current manure test reports/application rates.  If you have those pieces of information for your farm, you are in a good position to try using this tremendous tool during the 2016 growing season.Adapt-N rec

What if I think the recommendation is wrong or scarily high or low? 
Adapt-N WILL generate a recommendation, but we still need to use common sense.  If the recommendation seems too high or too low, the reasons for that need to be investigated.  An artificially low soil organic matter level will result in an extremely high N-recommendation and visa versa.  I worked with a farmer last year whose soil test report indicated 1% soil organic matter.  That is a very low number for Vermont, but I put it in.  It yielded a MASSIVE N-recommendation.  The farmer said, ‘I never put any sidedress N on and I always get 25-ton corn.’  Well, he was right.  The corn field looked great except for some spots around the edges that were torched/stunted from N-deficiency; the stalk nitrate test also indicated that the plants had adequate amounts of nitrogen available to them.  The places in the field that were clearly N-deficient were likely extremely sandy and represented low organic matter and high levels of leaching.  The soil organic matter level in the field overall was probably significantly higher than 1%.  It is a good tool, but it still needs to be informed by common sense and experience.

Two other virtues of the program compared with the PSNT:  1) you can get set up in Adapt-N now rather than late-June (as with the); and 2) it will email you nitrogen status updates on a regular basis, informing you of any major nitrogen loss events.

If you are interested in using this program for the 2016 growing season, get the aforementioned records together and contact me ( or 802-535-7922). I would be glad to show you how to run the program and help you get recommendations for several management zones (at least) on your farm.  Agronomic Technologies (the company that owns the Adapt-N license) has given me quite a few acres ‘free’ to introduce the product to farmers, other acres can be covered for about $2.50/acre.

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New UVM Nitrogen Recommendations for Corn are Coming!

With genetic improvements that have increased corn yield potential and the advent of good alternative approaches for determining in-season crop nitrogen need (i.e., sidedress N), it is evident that the UVM recommendations for nitrogen fertilizer on corn need to be updated.  While the entire document Nutrient Recommendations for Field Crops in Vermont will be revised next year, we will soon (within the next day or so) be releasing an addendum to that document that will serve as the UVM nitrogen recommendations for corn production during the 2016 growing season.  The revisions are not earth-shattering, but do account for the aforementioned realities.  Stay tuned!

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Better Bunker Silo Management

In this video from the 2016 Vermont Agronomy Plus series, Dr. Limin Kung, Jr. (University of Delaware) describes best management practices for minimizing the losses and optimizing the quality of feed stored in bunker silos. Small management changes can have big economic implications for your farm!

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