I think one should also ask himself if this method is acceptable for other applications outside of soil sampling.

I think a good analogy would be in the pharmaceutical industry and medicinal drug dosing.

Let’s suppose for a moment that I am a researcher for a leading pharmaceutical company and I have discovered a drug that prevents cancer. I know through my research that all persons can benefit from this drug but dosing needs to be established based on each individuals cancer risk. Those with a high risk should take 40 mg of the drug, 30 mg for an elevated risk, 20 mg for a slight risk, and no treatment for a near zero risk.

However, a problem arises with determining risk.

I know that screening every person for risk is time-consuming and expensive. It’s unreasonable to expect people to get screened because most won’t be able to afford it. However, I know that the benefits of the drug are so great that people need to be taking the drug so I devise a plan to determine the dosing requirements without testing each individual person.

What I decide is to break up all the landmass of the U.S. into “zones” based on common cancer risk. The already determined state boundaries provide an excellent basis for establishment of these “zones” because there is already data collected for each state, thus saving me a lot of time and expense in determining dosage requirements. Based upon my research, I determine the appropriate dosage for the inhabitants of each “zone” as follows:

The residents of states highlighted in red will receive a 40 mg dose, residents of states in orange will receive a 30 mg dose, residents of states in light blue will receive a 20 mg dose, and residents in the dark blue states will not need to take the drug.

Now the important question is if this is an acceptable way to determine individual dosing requirements? I think the obvious answer is NO! In each state we still have a large amount of variability. There are people who would benefit from a larger or smaller dose than the state average calls for, thus, a “zone” approach is vastly deficient. But yet we deem this same approach as acceptable for determining nutrient requirements for our crops. Even though there are areas within each arbitrary “zone” that would benefit from a higher or lower rate of nutrient, we are comfortable with a “zone” average. It doesn’t make a whole lot of sense!

The only good way to determine nutrient levels of the soil is by grid sampling rather than arbitrarily established “zones” which are not related to fertility. Grid sampling allows for an unbiased measurement of a fields fertility, which in turn, gives you the most accurate result. In the end, it will make you more money.

At the center of this claim is the fact that when fertilizer is broadcast, in the case of Phosphorous, approximately only 20% of the material is available to the plant in the year of application.The company agronomist claims that his product increases the percent available in the first year from 20% to about 50%, thereby allowing for reduced rates.

I asked him if using reduced rates would pull the soil levels down over time and he answered with a very confident “no”, but when we delved into the topic further, he could not explain how this would not happen.

I presented this agronomist with the scenario that if I applied 60 lbs. of P2O5 and the plant removed 80 lbs. of P2O5, where did the other 20 lbs. come from? He could not answer this simple question.

Of course it’s very obvious where the plant obtained the other 20 lbs. of nutrient; it came from the soils reserves. So if it came from the soils reserves, the soil test level will drop over time, or in other words, the soil is being mined of that nutrient.

I think it’s very important that people understand exactly what “efficiency” means. When “industry experts” talk about fertilizer efficiency, they are not talking about reducing the amount of nutrient the plant needs in order to produce a crop. Rather, they are talking about the portion of applied product that remains available to the crop in the year of application.

The take home message of all this is that if you apply less nutrient than the plant removes, soil test levels will fall and eventually yield will be adversely affected.

In a side-by-side comparison we always have 2 sides. Your probably thinking “well duh!”, but stick with me. Those 2 side can be anything, i.e., 2 halves of a field, 2 passes of a sprayer, 2 passes of a planter, etc., etc. What’s important to consider is the fact that even before treating the 2 sides with the product you are evaluating, those 2 sides will never yield the same. What this means is that one side will always have an advantage over the other, right from the start. Personally, I’ve seen as much as a 25 bu. yield difference between 2 eight row passes with a combine. Usually the variance is in the 5-7 bu. range, but it often can be more.

If  I have a product to sell, a side-by-side plot is my best friend. Because the 2 sides never yield the same it means that I have a 50% chance of winning the plot even if my product does nothing. I’ll take those odds because half of the people who try my product will be satisfied and I’ll have a great base to build upon.

This doesn’t mean that side-by-sides are completely useless. The trick is to have multiple side-by-sides in a given year for a given product. These multiple side-by-sides can be accomplished not only in the same field, but in multiple fields. If you want to do a split field, do it on multiple fields. In order to get accurate data that can be trusted, it is generally recommended to do at least 6 replications. If you do split fields, split 6 different fields. If it’s by planter width, set up 6 different trials by width.

No matter how you do it, it’s important to replicate! Then, if you see a yield advantage across multiple trials, you can be much more confident that the product you are evaluating is actually providing a benefit. Yes, it does take more time to do it in this manner, but in the end you’ll be money ahead.

____________________________________________________________________________________

**Added 12/2011**

Crop: Corn

Title: Research Conducted By: Agro-Culture Liquid Fertilizers

Product Tested: Coron, High NRG-NR

Summary & Results: Research conducted in years 2005, 2006, 2008, and 2009. No statistically significant yield increases were observed.

URL: http://www.agroliquid.com/assets/Research/Research-data/corn-foliar.pdf

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**Added 12/2011**

Crop: Corn

Title: Research Conducted By: Iowa Soybean Association

Product Tested: Coron

Summary & Results: CoRon yielded -2.6 bu./acre compared to untreated check.

URL: http://www.isafarmnet.com/09STResults/Calhoun/st2009345C.pdf

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Crop: Corn

Title: Missouri Soil Fertility and Fertilizers Research Update 2009, ’Foliar Fertilizer and Fungicide Interactions on Corn’ (pages 91-97)

Research Conducted By: University of Missouri

Product Tested: Coron, PacerN, Various other fertilizer materials

Summary & Results: “The incidence of disease was not affected by fertilizer treatments.”

“There was a significant increase in grain yield (17 bu/acre) when 30-0-0 was applied to corn at VT at Novelty and Portageville.” [all other foliar materials showed no significant yield increase]

URL: http://aes.missouri.edu/pfcs/research/prop09.pdf

__________________________________________________________________

Crop: Corn

Title: Fertilizer Placement Options Demonstration

Research Conducted By: UNL South Central Agriculture Laboratory; Glen P. Slater, Richard B. Ferguson

Product Tested: Coron

Summary & Results: “There is little evidence that foliarly-applied Coron was able to replace N which was not supplied by NH3 at V6.”

URL: http://scal.unl.edu/Fertility/Fertilizer%20Placement%20Demo%202009%20Report.pdf

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Crop: Corn

Title: Corn Response to Foliar Coron Applications with Reduced N Rates (2002)

Research Conducted By: Mississippi State University; R.R. Dobbs, N.W. Buehring, M.P. Harrison

Poduct Tested: Coron, Urea

Summary & Results: “Foliar applications of Coron or urea had no effect on corn yield, and there was no foliar application by soil N rate interaction. Averaged over foliar applications, yields were increased from 184 to 203 bu/ac as soil N rates increased from 140 to 200 lb N/ac rates.”

URL: http://msucares.com/nmrec/publications/2002/corn/rotation/dobbs01corn3856.pdf

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Crop: Corn

Title: Corn Response to Foliar Coron Applications with Reduced N rates (2003)

Research Conducted By: Mississippi State University; M.P. Harrison, N.W. Buehring, R.R. Dobbs

Product Tested: Coron

Summary & Results: “Foliar applications of Coron had no effect on corn yield and there was no foliar application by N rate interaction. Averaged over foliar applications, yields increased from 150 to 173 bu/acre as soil N rates increased from 119 to 170 lb N/ac.”

URL: http://u5s1ea.bay.livefilestore.com/y1pHn7ARyChkaDUSg_mGrPQyCCdEC03-ArmLVuluf5QmyPXZQNCgs7zGlz108d4HEKC5BfZyLeY36bDzcpw1-EQeKtQqHYf-nTm/Corn%20Response%20to%20FoliarCoRoN%20Applications%202003.pdf?download&psid=1

__________________________________________________________________

Crop: Corn

Title: Coron Nitrogen Study on Corn – 2007

Research Conducted By: Becks Hybrids, Illinois PFR Center

Product Tested: Coron

Summary & Results: “Overall, Coron treatment yielded an average of 13 Bu./A. less than the traditional 200# rate in a 100# 28% pre-plant and a 100# 28% side-dress. From 1-5 gallons/A. there was only a 1.7 bu./A. difference between Coron treatments. This would indicate that most of the nitrogen used was received from the 150# pre-plant and the post application of Coron at V12 did not supply much benefit to the corn crop. After accounting for the cost of nitrogen, Coron treatment averaged a net return loss of $36.40 per acre compared to the control.”

URL: http://www.beckshybrids.com/research/2007/pg112.pdf

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Crop: Corn

Title: Missouri Soil Fertility and Fertilizers Research Update 2008, ’Foliar N Efficiency Experiment’ (pages 57-58)

Research Conducted By: University of Missouri

Product Tested: Coron, Urea, UAN

Summary & Results: “Foliar Treatments did not show superior ability to deliver in-season N to a corn crop relative to soil applied treatments.”

• “Average yield with foliar N was 119 bu/acre, with soil-applied N was 127bu/acre.”
• “Foliar urea gave significantly higher yield than foliar Coron or foliar UAN.”

URL: http://aes.missouri.edu/pfcs/research/prop08.pdf

__________________________________________________________________

Crop: Corn

Title:  Missouri Soil Fertility and Fertilizers Research Update 2008, ’Foliar Fertilizer and Fungicide Interactions on Corn’ (pages 126-131)

Research Conducted By: University of Missouri

Product Tested: Coron, Pacer N, Various other fertilizer materials

Summary & Results: “There was no significant increase in grain yield when foliar fertilizers were applied to corn at VT. Some foliar fertilizers reduced grain yield 14 to 24 bu/acre when compared to the non-treated control in 2008.”

URL: http://aes.missouri.edu/pfcs/research/prop08.pdf

__________________________________________________________________

Crop: Soybean

Title: 100 Bushel Soybean Study – 2009

Research Conducted By: Becks Hybrids, Illinois PFR Center

Product Tested: Coron, Sable

Summary & Results: “Both Sable and Coron foliar nitrogen treatments did not offer yield benefits. Applications were made later at the R4 growth stage and this may have been too late for these products.”

URL: http://www.beckshybrids.com/research/2009/pg126-127.pdf

____________________________________________________________________________

Crop: Soybean

Title: Becks Foliar Fungicide and Insecticide Study – 2006

Research Conducted By: Becks Hybrids

Product Tested: Coron

Summary & Results: [Foliar applied Coron provided no benefit]

URL: http://www.beckshybrids.com/research/2006/pg65.pdf

__________________________________________________________________

Crop: Soybean

Title: Foliar Fertilization of Roundup Ready Soybeans

Research Conducted By: University of Delaware; Gregory D. Binford, Brian K. Hearn, Mark A. Isaacs, David J. Hansen, Richard W. Taylor

Product Tested: Coron, Ele-max (Mn), Norcrop, Nutrition Plus

Summary & Results: “This research shows no benefit from mixing foliar fertilizers with glyphosate during application to RR soybeans on Coastal Plain soils in the Mid-Atlantic Region. In addition, the application of N fertilizers during early reproductive growth results in no yield benefit within the yield range and growing conditions observed in this study.”

URL: http://www.plantmanagementnetwork.org/pub/cm/research/2004/rr/

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Crop: Wheat & Barley

Title: Studies on slow-release liquid fertilizers applied at low rates as a foliar application on North Dakota spring wheat/winter wheat [multiple studies]

Research Conducted By: North Dakota State University, David Franzen

Product Tested: Coron, GP 30-0-0 foliar, N-Pact, UAN

Summary & Results: [no significant differences from foliar products across all studies]

URL: http://www.soilsci.ndsu.nodak.edu/Franzen/Franzen_Publications/foliarNreport.pdf

__________________________________________________________________

Crop: Wheat

Title: Evaluation of Greenseeker System in Wheat

Research Conducted By: Brian Vulgamore, Vulgamore Family Farms

Product Tested: Coron, Greenseeker

Summary & Results: “Be careful when considering alternatives to traditional fertilizer”

URL: http://www.ksagresearch.com/conference13/Research%20pdf/Vulgamore_NrichStudy.pdf

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Crop: Wheat

Title: Wheat Response to Late-season N Application for Protein, Carrington, 2005

Research Conducted By: North Dakota State University; Greg Andres and Blaine G. Schatz

Product Tested: Coron, UAN

Summary & Results: [No increase in yield or protein from foliar applications]

URL: http://www.ag.ndsu.nodak.edu/carringt/agronomy/Research/Fertility/05%20HRSW%20Response%20to%20N%20for%20Protein.pdf

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Crop: Wheat

Title: Foliar Application of Nitrogen Fertilizer on Winter Wheat

Research Conducted By: Michigan State University Extension; Martin Nagelkirk

Product Tested: Coron, GP exp, Pacer N, UAN

Summary & Results: “None of the N treatments improved grain yields above the control.” “Yields tended to be slightly depressed by foliar treatments…”

URL: http://u5s1ea.bay.livefilestore.com/y1pEIy5xpc8K_cin5jnB-JvFv2WdStgSa0P-Y7A3UoMEEl9eAN75snhFinU9Ay36-GIYisDNFBUcWyBSfF9HFRxeliTGcZKv_Tj/Foliar%20Application%20of%20Nitrogen%20on%20Winter%20Wheat.pdf?download&psid=1

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I was walking through knee high corn and found it sliding across the ground. At first I thought it was a slug but it was moving much too fast. If you haven’t guessed by now, it’s a leech. In 20 years of walking fields this is the first one I have ever found.

     So how do we know if they work or not? The first step in evaluating these products is to look at the agronomics behind the stated benefits. With many companies claiming nutrient use efficiencies through foliar feeding, as well as a long window of availability through “controlled release” formulations, it’s imperative that we understand just how these products work.

Foliar Efficiencies

     One of the main selling points of foliar applied nutrients is the increased efficiency of foliar application versus soil applied applications. One of the more popular foliar N products on the market even goes so far as to claim that 1 pound of foliar N can replace 5 pounds of soil applied N, for a 5:1 efficiency ratio. But is this true?

     Plant leaves, by design, are not very efficient in taking up nutrients. Instead, they were designed for a different purpose. Darren Goebel, Area Agronomist with Pioneer Hybrids addressed this subject in an article last summer. He said;

… leaves are designed to collect sunlight, photosynthesis, transport sugars to other parts of the plant and transpire water vapor and gases. Leaves are covered by a waxy cuticle, making them virtually impervious to water and carbon dioxide. Stomata make up 10% of the leaf surface and account for 90% of the water and gas movement on the leaf.

   Goebel goes on to say this;

Because such small amounts of nutrients can enter plant leaves, macronutrients like nitrogen, phosphorus, and potassium should not be considered for a one-or two-shot foliar feeding program. It is highly improbable that foliar feeding can get enough of these nutrients into the plant to make a difference. In fact, several University studies have confirmed little difference in yield when foliar applying macronutrients to corn and soybeans.

     Obviously there isn’t much of a gain in efficiency when trying to feed macronutrients through the leaves of the plant; the plant is not capable absorbing nutrients in large enough quantities to do much good. However, if you have seen the advertisements for these products, you know that the inability of the leaf to absorb large amounts of nutrients makes no difference because you only need a small amount of product to see a sizable yield increase. In fact, most of these products have a recommended application rate of 1-3 gallons per acre, which at 2.5 lbs. of nitrogen per gallon, definitely qualifies as a small amount of N being applied.

     Most of these products are recommended to be applied with glyphosate as a planned application program. At this time – especially in corn – the plants N usage is beginning to increase rapidly. This also coincides with the particular growth stages when the plant is determining ear size (corn) and setting pods (beans). The theory behind this is that a little extra N at this critical time can pay big dividends. The question is; is there any validity to the theory? We shall see.

Note: From here on, I’m going to focus on corn, but what I am going to say can certainly be applied to beans also.

     As I mentioned previously, at the time these products are recommended to be applied, the plants N usage is increasing at a rapid rate. As you can see from the chart below, a corn plant’s N consumption increases from 1.5 lbs. per day for 4″ corn to 6.0 lbs. per day when the corn is waist high. This is the period of time when foliar applications are recommended because you want to make sure the plant has enough N when it needs it the most. In theory, this makes a lot a sense. Although one must remember that this is theory – reality is usually somewhat different.

     Lets assume that we have a normal corn crop. The corn was planted in a timely fashion, we have a good stand, and the corn is not showing any N deficiencies. In this example, it is recommended that we apply 1 gallon of a 25% controlled release nitrogen product with our normal glyphosate application. Since it’s a 25% N containing material and it weighs 10 lbs. per gallon, we are applying 2.5 lbs. of nitrogen per acre.

     Under normal circumstances, the timing of the glyphosate application would occur around the V5 to V6 growth stage. Looking at the N use chart, we can see that at the V5-V6 stage the corn plant is using somewhat less than 6.0 lbs. of N per day. We know at this point, the corn plant is just beginning a period of extremely rapid development so we can safely assume the plant is using between 3 and 4 lbs. of N per day. It’s important to note that the plant is using this amount regardless of whether it is taken up by the roots or absorbed through the leaves.

     Given the above facts, it’s obvious that the 2.5 lbs. of N we are applying with the foliar product is not even supplying enough nitrogen to feed the plant for one day. But in reality, the plant is not receiving the full 2.5 lbs. because not all of the product is being intercepted by the plant. A significant portion of the material is hitting the ground rather than the leaves.

     When spraying corn that is approximately 16″ tall (V6), the crop canopy intercepts approximately 50% of the spray (assuming nozzles positioned both directly over the row and between the row), which results in an application of only 1.25 lbs. of N to the crop. This is barely enough N to feed the plant for 1/2 a day. Now we begin to see the futility in foliar feeding macronutrients. But there’s more to the story, so let’s continue. 

     From the label of the product we are using, 75% of the N is in the urea form with the remainder in a slow or controlled release form (I’ll have more on controlled release later). With urea nitrogen, approximately 70% of the N is absorbed into the leaf within the first 24 hours – the rest of the N is lost. If we plug the 70% figure into our calculations, only 0.875 lbs. of N is being absorbed by the plant. This is only enough N to feed the plant for 6 hours. By this point I’m sure somebody is going to bring up the fact that they use more than 1 gallon of product, but even at the 3 gallon rate, we are supplying enough N to feed the plant for 18 hours instead of 6 hours. This is still a minute amount of N when compared to the plant’s needs.

Slow Release Formulations

     Another argument that frequently comes up is the fact that the product is slow or controlled release, thereby spoon-feeding the crop over a 3 to 4 week period. Assuming that all the N being applied is in the slow release form (as implied through the advertisements), 0.875 lbs. of N spread over a 4 week period only amounts to 0.031 lbs. of N available to the plant per day.  But we know this is not the case because only a small portion of the N is in the controlled release form.

     Remember the label stated that 75% of the N is in the urea form. This means that only 25%, or 0.63 lbs., is in the controlled release formulation. If we take 0.63 lbs. and divide that by a 4 week period, we come up with 0.0225 lbs. of N provided to the plant each day. To you and I, this would be like taking 1 milligram of Human Growth Hormone (HGH) per day when the recommended amount is 165 milligrams, and expecting to look like Arnold Schwarzenegger in a few weeks; it’s not going to happen. And so it goes with slow release nitrogen. The plant is receiving such an infinitesimally small amount of nutrient, it is not possible to affect a positive change in the crop.

Conclusions

     Although the theory sounds good and the sales pitch can be very convincing, foliar feeding macronutrients such as nitrogen is just not feasible. Because plants require such large amounts of these nutrients (it’s why they are called macronutrients) over an extended period of time, and because leaves are not designed for the absorption of nutrients, it’s physically impossible (without harming the plant) to introduce enough nutrient into the plant in order to gain a benefit. A person should look upon these types of products with a skeptical eye and weigh the stated claims against known agronomic principles. Oftentimes, one will find that the claims just don’t add up.

There is no doubt that zone sampling saves money versus grid sampling. With grid sampling, in order to ensure an acceptable degree of accuracy, a lot of samples need to be pulled and analyzed which drives up costs. Conversely, zone sampling reduces costs because it is assumed that given areas within a field, as one poster in a thread below so eloquently put it, are homogeneous. In other words, the variance in pH and nutrient levels are minimal so these zones can be sampled as a composite, thus reducing costs. But is this true? Are zones homogeneous enough that we can in fact reduce sampling frequency in order to reduce costs? I have found that the answer to that question is usually a resounding no. Here’s why…..

Over a period of several years, I have had the opportunity to grid sample a number of fields on 1.1 acre grids. This has provided me with the ability to view nutrient variability on a scale not typically seen in the industry. With this density of samples, I not only get an excellent look at field scale variability, but I can also measure the variability within differing soil types within the field. What I consistently find is that with respect to P & K levels, they are not homogeneous within these zones - although pH is a different story.

Here is a field showing sample points on 1.1 acre grids and also the different soil types:

The next image is the field broken into different sampling zones based on the soil types seen above:

Now that the field is broken down into sampling zones based on soil types, an analysis of the samples that fall within each zone can be done.

After breaking down the samples within their respective zones, it becomes quite apparent that there is a lot of variability within the zones themselves. In order to get an idea on how large the variability actually is within the zones, I did a standard deviation calculation on each zone. Keep in mind that the standard deviation is the average variation from the zone average. For P & K (actually P2O5 & K2O), it’s easy to see that the variation is quite large, and for pH, the variation is somewhat smaller. But what does all this mean? And how does it affect the amount of fertilizer that is recommended to be applied?

The next step is to calculate the average amount of error as compared to the zone average:

This chart shows the percent error of the zone average when compared to the individual samples (the chart is labeled incorrectly). In other words, the zone average over/underestimates the nutrient level by the listed percentage. Clearly we can see that for P & K, using the average for the zones results in a large amount of error. A person needs to keep in mind that over/underestimating the level of fertility directly affects the amount of fertilizer being applied by roughly the same percentage. So in effect, if I were to use the zone average as a basis for a fertilizer recommendation, I would be overapplying or underapplying P by approximately 40% and K by 20%. In my opinion, this is unacceptable.

I do think anything under 10% is acceptable, so for pH and the application of limestone, using a composite average by zone is a viable alternative. But not for P & K.

I know someone is going to bring up the fact that this is only one field and I am cherry-picking the data. I have run many of these analysis on different fields it it almost always comes up the same. Very seldom does a composite sample by soil type accurately reflect the P & K fertility within that zone. Again, pH is a different story. In the majority of fields, pH correlates fairly well with soil type, so a zone composite is usually acceptable. But who is going to sample pH by zone and P & K by grid? It’s simply not feasible so grid sampling is the best option and far superior to zone sampling.

I will add one caveat however. Zone sampling for mobile nutrients such as nitrogen may produce acceptable results, but since we do not sample for nitrogen in Illinois, I have not done a similar analysis.

So now, the question becomes: at what point/date should a person make the switch? Leave it to Bob Nielson at Purdue University to come up with some timely information on this very subject!

I would highly recommend everyone read Bob’s excellent article. He not only looks at average frost dates, but he also discusses a not entirely well known phenomena of a hybrids ability to adjust it’s GDU’s downward the later it is planted.

Be sure to check out Bob’s article.

Late Planting/Replanting & Relative Hybrid Maturity

Just a quick note on planting progress…

Corn planting is nearly finished in this area. I would expect by Wednesday, most farmers will be done with corn and starting on bean planting. I’m sure this comes as a disappointment to the ethanol doomsayers who have been predicting a lower yielding corn crop because of planting delays, but the fact is, the corn crop will be just fine. We generally see little to no yield penalty if the crop is planted before May 15.

For the most part, the wheat in this area is mostly good to excellent. I’ve been out in a few fields and at present, there is no disease to speak of. This could change quickly if warmer temps are accompanied by additional rainfall, but for now, diseases are being held in check. It looks like those who chose to make an early fungicide application did so needlessly. If you are considering applying a fungicide at flowering, please use the Wheat Disease Prediction Tool I posted about earlier. This will help to avoid further unneeded applications.

So who’s right and who’s wrong?

I was going to make a long post detailing the answer to this question, but instead, I’ll let you decide for yourself.

 Sources: Historical Crude Oil Prices & Historical Grain Prices