Four questions: nitrogen on grass, starter fertilizer on corn, “More than Manure,” sulfur and boron fertilizer for corn

 

Ag Clients,

Several questions have recently come up, and I thought I would try to share concise answers with those of you who may be facing similar questions at this point.  As you would expect, Extension employees need to be careful how we discuss particular products.  We cannot and should not endorse them, but sometimes we need to scrutinize products to the best of our ability.  My hesitation about certain products also should not be interpreted as an accusation of fraud against the company, but rather my judgement that the ‘data’ offered as evidence of effectiveness does not come close to what I think a minimum threshold ought to be for farmers looking for assurance of return on investment.

Please let me know if you have any questions about this or other agronomic issues.

Daniel Hudson, daniel.hudson@uvm.edu
Question 1: How much nitrogen should I apply to my grass haylage fields?

The answer to this question comes in several parts, many of them can be found in the publication “Nutrient Recommendations for Field Crops in Vermont” which can be accessed at http://pss.uvm.edu/vtcrops/articles/VT_Nutrient_Rec_Field_Crops_1390.pdf.  The optimal timing for the first application of nitrogen fertilizer to grass has already passed, but the points below still have implications for the rest of this year and in the future:

  • Plants will be more responsive to nitrogen (whether from manure or synthetic fertilizer) if the soils are not acidic (and/or do not contain high levels of reactive aluminum) and contain adequate levels of phosphorus (P) and potassium (K).  Ideally, the pH in a grass field will be between 6.2 and 6.8.  Arriving at these conditions amount to the ‘low-hanging fruit’ of soil fertility, and will ensure the best response possible to any nitrogen that you add to the system.
  • In the past, it has been said that an economic response to nitrogen fertilization can be realized up to a rate of 200 pounds per acre (actual N, regardless of source).  The economics of various rates will change with the price of N and the value of the resulting forage.
    • Yield responses to added nitrogen are highly variable.  A moderate yield response to the first 40 lbs. of N fertilizer per acre would be 25-40 pounds of DM per pound of N added to the system.  That would translate to about 1,000 – 1,600 pounds of grass DM from 40 pounds of N applied.  Of course, this will be influenced by the stage at which the grass is harvested.
    • The second 40 lb. fertilizer increment added would be expected to have less of an impact, although it may still be economically beneficial.
  • Grass fields that receive nitrogen (from whatever source) will usually have a higher protein level.  The amount of increase will vary with grass species, timing of application, and stage of harvest.  Grass with adequate access to nitrogen will send up more tillers, resulting in a more leafy plant.  These plants will generally be larger than their unfertilized counterparts when compared at the same stage of plant development (e.g., early-boot stage).  For most experienced hay producers, it is intuitive that leafier forages (high leaf:stem ratio) will be higher in protein than those for which the leaves contribute a small percentage of the total forage DM..
  • Rates of more than about 80 pounds of actual N should be split, applications being made before significant growth occurs in the spring and/or before significant regrowth occurs between cuttings.  This will reduce the chances of losing the expensive nitrogen fertilizer that you applied.
  • The first increments of fertilizer applied give you the “biggest bang for your buck.”  Diminishing marginal returns are the rule, and the “break-even” varies depending on situation.
  • Dairy manure clearly has nitrogen in it, and this should be accounted for when deciding how much to top-dress.  You cannot account for what has not been quantified, so it is essential to have the manure tested.  Method of application and weather during and after application will influence how much nitrogen actually makes it into the soil.  Surface application followed by hot, windy, sunny weather maximizes your chances to lose a large percentage of the ammonia fraction of the nitrogen in the manure.
  • If you expect that less than 20% of the forage dry matter (DM) present at harvest will be from legumes, the field should be fertilized as though the legume is not there.
    • Between 20% and 60% legume DM, yields still might be increased by an early application of about 40 pounds of actual N (i.e., before green-up).
    • Stands between 20% and 40% legume likely will benefit from a second application of N later in the season.
    • We do not recommend that fields with more than 60% legume (by DM) receive additional nitrogen fertilizer.
  • Legumes that don’t have to fix nitrogen of their own won’t.  Lots of N in the environment favors the grasses, and discourage legumes from turning on the cellular machinery that  results in ‘nitrogen fixation’, a process that grasses cannot accomplish.
  • Some species of grasses are more responsive to nitrogen fertilizer than others.  The ryegrasses, while famous for their forage quality, are also famous for their appetite for nitrogen.

 

Question 2: Should I use starter fertilizer on my corn?  If so, what kind and how much?

We should first define a few terms up front.  ‘Starter fertilizer’ is generally placed two inches below and two inches to the side of the row where the seeds are placed (i.e., 2X2).  Starter fertilizer is less often deep-banded or applied in surface bands, so in the context of this article, ‘starter fertilizer’ refers to 2X2 placement.  ‘Pop-up’ fertilizer is a liquid fertilizer product that is placed in the furrow with the seed.

Will starter fertilizer increase the yield or quality of my corn?

Understanding that nobody is expecting a ‘yes’ or ‘no’ answer on this, I will start by mentioning factors that affect the potential benefit of using starter fertilizer in corn:

  • Soil temperature
  • pH and level of soil fertility
  • Land tenure (how long you will be renting it)
  • Tillage system
  • Crop residue
  • Fertilizer price
  • Soil texture

Conditions in which starter fertilizer is more likely to provide an economic benefit include: reduced tillage, heavy surface residue, low levels of P and K, high or low pH, and low soil organic matter.  Under these conditions, using starter fertilizer can improve early crop growth, increase yield, hasten crop maturity, improve phosphorus use-efficiency, and carry micronutrients (which may or may not be needed).

Table 1.  Probability of crop response to starter fertilizer.

AVERAGE daily soil temp at 2 in. Response probability*

45-50ºF

High

50-55ºF

Moderate – High

55-60ºF

Low – Moderate

over 60ºF

Low

*assuming soil P levels of 4.1-7 ppm using the Modified Morgan extraction method.

 

Table 2.  Potential for yield response to phosphorus in starter fertilizer

Planting Date*

P Test**

Min. Till

Conv. Till

Early (Before May 7)

less than 4.1 ppm

high

high

4.1 – 7 ppm

high

moderate

over 7.1 ppm

moderate

low

Normal (May 7 – May 21)

less than 4.1 ppm

high

high

4.1 – 7 ppm

high

moderate

over 7.1 ppm

moderate

low

Late (After May 21)

less than

high

high

4.1 – 7 ppm

moderate

low-moderate

over 7.1 ppm

low

low

*Highly variable by location in VT.  To adapt the table for your area, change the ‘early’ date what you estimate to be the average of your earliest planting dates ever and plug it in instead of May 7.  Adjust the other dates accordingly, and you will have a reasonable estimate of potential response, with the assumption that soils will be warming from one date to the next.

**Using Modified Morgan  extraction method.

 How much starter fertilizer should I use?

Up to 90 pounds of phosphorus (P2O5) can be band-applied.  The only reason to band that maximum amount, however, would be if your soils have critically low P levels, and/or high levels of reactive aluminum.  If soil test levels are in the optimal range but soils are very cool, only 20 – 40 pounds of phosphate (P2O5) are needed to realize the maximum benefit until soils warm up enough for existing soil phosphorus to become available.

Potassium and nitrogen fertilizer can also be band applied, but should be included at a maximum combined (N +K2O) total of 70 pounds per acre. Higher levels can cause salt stress to seedling roots, resulting in crop injury or death.

The major lesson here is to look at your soil tests.  If cash is a limiting factor, rank your fields based on which ones are low in P, cooler, wetter, contain more reactive aluminum, etc.  In soils in the optimum and high range for soil P (4.1-7.0 ppm), the argument for using starter fertilizer diminish as the soils warm up.

Generally speaking, use the least expensive (considering total pounds of actual nutrient delivered) forms of fertilizer available.  Different forms of fertilizers have varying degrees saltiness (i.e., ‘salt index’) but if they are placed 2X2, you should not have a problem as long as the rates are kept in the ranges discussed above.

‘Pop-up’ or Seed-Placed Fertilizer

‘Pop-up’ fertilizer is generally a liquid formulation that is placed in the furrow with the corn seed.  It should not be used with soybeans due to salt-sensitivity issues.  I cannot emphasize enough that MORE IS NOT BETTER when it comes to seed-placed fertilizers.  While maximum allowable (i.e., ‘safe’) levels vary depending on who you ask 8 – 10 pounds (total N + K2O) are the highest numbers I have seen recently, and it should be less in sandy soil.  In general, 5 pounds of total N + K2O per acre of seed-placed fertilizer is considered to be a rate that will not cause seedling injury, even in sandy soils.  Be sure that each individual row applicator is calibrated.  Last year I saw a dramatic example of what happens when some of the rows are delivering an excessive rate.  Emergence was delayed by at least 10 days in the rows where the rate was intentionally excessive, the injury being much worse in the sandy spots.  The farmer decided not to replant (which turned out to be a very good choice), but there was a visible difference between the rows throughout the growing season.  Seed placed fertilizer should never contain urea or volatile ammonia.  Finally, never place micronutrients (boron, copper, molybdenum, cobalt) near the seed.

 

Question 3: What about this product called “More than Manure”?

Multiple farmers have asked me about my knowledge of a product from Specialty Fertilizer Products (SFP) called “More than Manure®.”.  In some cases, the farmers easily spent more than $4,500 on the product.

More than Manure® (MTM) is a “Mixture of maleic-itaconic copolymer partial calcium salt and maleic-itaconic copolymer partial ammonium salt” (i.e., seemingly a mixture of Avail® and Nutrisphere-N®).  SFP recommends that about 18 ounces per acre for the liquid formulation be used.  Interestingly, maleic and itaconic acid are also used in at least some fabric softeners and possibly other fabric conditioning products.  Based on the nature of the compounds, it seems very likely that these products will decompose over time, as indicated by the manufacturer.  That said, even if it does work, it will need to be applied over and over again to achieve whatever results there may be.

SFP promotes MTM as a means of reducing N loss and increasing phosphorus availability.  The company is well known, and has been heavily promoting the product on RFD-TV.  The MTM website is very professional, and there are nice farmer testimonials.  Being as susceptible as anyone to advertising, I often have to remind myself that no matter how nice product testimonials are, they are a marketing tool and are no substitute for data.  At this point the data presented as support for MTM is not compelling.  While they ‘document’ yield increases in various settings, it should be noted that most of the studies are carried out by elevators that likely sell the product.  A bigger concern, however, is that no details about the experimental designs are given, and there are no names or contact information given for the respective studies.  The one study that references a university research farm, upon further investigation, had no details either.  The technician that carried out the study has retired, and the work was not peer-reviewed or published.  Thus, the best that can be said about the any of the data that I have seen that is used to promote the product is that it is anecdotal.  Much more could be said on this subject and I would be very glad to talk with you if you want more information about the proposed mode of action of the ingredients of this product or more information other independent research that has been conducted using the active ingredients of MTM.

If the YouTube video that I have seen (posted by the company) is accurate, introducing the product into the manure pit does initiate a rather entertaining bubbling reaction.  Unfortunately, bubbles in your manure pit do not necessarily mean that you will recover even a dollar of what you might invest in this product.  Until compelling data from studies with a valid experimental design conducted by independent researchers is produced, I cannot recommend that farmers spend money on this product, and CCAs should be very careful  about suggesting that farmers will receive a financial return on their investments if they purchase and use this product.

If you try any such fertilizer conditioning product on your farm, be careful about drawing conclusions about the efficacy.  Treating one field and not another or one batch of manure in one field and another batch of manure (not treated) for a different field, does not account for other pre-existing differences that can easily affect the outcome: soil type, drainage, variety planted, weed control issues, manure history, planting date, etc.  Replication and accurate measurement of results are absolutely necessary in order to reach valid conclusions.

I am a big proponent of spending money on items that will more than pay you back, but the data does not give me confidence that this product is a good investment.  If it does not actually deliver the claimed results, a dollar saved ends up being a dollar in your pocket.

Question 4: What about Boron and Sulfur Fertilizer for Corn

Micronutrients are a perennial question for some crops, especially in some regions of the country.  In my experience, the most common micronutrient deficiencies in corn tend to be zinc and manganese, but I have not observed any such deficiencies in the part of Vermont where most of my time is spent.  Recently, a farmer asked me about boron and sulfur fertilizer for corn.  Looking at their soil test results from a commercial lab, sulfur was listed as ‘low.’  If you examine UVM soil test reports, you will notice that sulfur is not even listed.  This is not because sulfur is not needed for plant growth, but rather because sulfur deficiency tends not to be an issue in Vermont.  Most of the corn acres in Vermont support dairy farms and  as such, receive manure.  The manure provides plenty of sulfur to support the corn crop.  In the Midwest, where fewer acres receive manure and where industry upwind has cleaned up their smokestacks to the point that farmers can no longer count on free atmospheric sulfur (acid rain), sulfur deficiency can occur – but it is still very rare.  When it exists, it will generally be on cold, very sandy soil.  I have seen no evidence that sulfur fertilizer is needed on corn fields in Vermont.  When it exists, it should be worse in sandy areas of the field and will somewhat resemble nitrogen deficiency, except the leaves will be more yellow between the veins, especially in the younger leaves.

All plants need boron to grow, but in Vermont boron deficiency is only of significant concern in alfalfa.  As far as I know, boron deficiency in corn has not ever been documented in Vermont.   In fact, boron toxicity resulting from trying to fix a problem that you don’t have, is a far more likely scenario.

If you would like to learn more about nutrient deficiencies in field crops, these documents may be of use to you:

Nutrient Deficiencies (Iowa State):

http://extension.agron.iastate.edu/soybean/documents/nutrientdeficiency.pdf

Boron: http://nmsp.cals.cornell.edu/publications/factsheets/factsheet47.pdf

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About Daniel Hudson

Daniel is an agronomist for University of Vermont Extension in the areas of agriculture and nutrient management.
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