Tar Spot Update


Last week Dr. Damon Smith, with the University of Wisconsin, gave an update on Tar Spot and I thought his findings were extremely valuable and the most relevant information I have seen to date.

Tiny black spots against a brown lesion are a symptom of the tar spot complex in corn.


- Tar Spot can overwinter and has been in WI for 3 years. It is also in Eastern IA. The first two years Tar Spot was in Wisconsin, it did not infect plants until late August. This year it arrived Mid-June.

- There hasn’t been a single plant found with the Monographella version (the really bad type only found in Mexico so far)

- Tar spot is causing yield loss in the absence of any another disease, such as grey leaf spot.

- Hybrid tolerance incredibly variable. Some can handle it, some take a huge yield hit with this disease.

- Early hybrids take less of a hit. Research is showing that at 10% of the leaf area covered with Tar Spot yields are reduced by 8 bu/ac. Longer maturity (103-113 day) hybrids lost 15 bu/ac when 10% of the leaf area was infected.

- University plant pathologist are creating a phone app (the TarCaster) that will hopefully be able to predict the arrival of the disease based on the weather. They already have a similar program for predicting white mold. They expect that to be out for testing this upcoming year.

- Yield losses appear to be dependent on when the plants become infected with Tar Spot. For example, this year infection started between V8 and VT is some regions but in previous years infection did not start until after milk stage.  There is barely a hit on yield if it arrives during the Milk stage.

-Fungicide does help if timed properly, and at least Headline Amp and Delaro are labeled for Tar Spot.

-University plant pathologist plan on releasing a fungicide update around the end of December to show when the optimum time will be for applying fungicides to control/suppress Tar Spot.

What are Liquid Suspension Fertilizers

And Should I Consider Using Them On My Farm?


  • Liquid fertilizers offer some unique advantages compared to dry granular fertilizers:
    • Accurate nutrient application distribution
    • Can be tank mixed with many pesticides
    • Macro and micro nutrients can be evenly blended
    • Can be easily surface or subsurface banded
  • Liquid suspension fertilizers offer the same unique advantages and are cost competitive with dry granular fertilizers.
  • A recent summary of 39 science-based studies showed that banding fertilizer reduced phosphorus fertilizer fixation in the soil, caused roots to concentrate in nutrient rich fertilizer bands, and resulted in increased nutrient uptake and 4.5% higher corn yields.
  • Local on-farm research shows that surface banding liquid suspension fertilizers on 15" centers increases corn yields by 4.2 bu/ac and profitability by 16.7 $/ac compared to broadcasting equivalent rates of dry granular fertilizer.

Liquid Fertilizers – Some Unique Advantages

Liquid fertilizers offer unique advantages over dry granular fertilizers. Liquid fertilizers can be applied extremely accurately, can be tank-mixed with many different pesticides, and micro nutrients can be evenly blended in liquid solutions. These factors result in uniform nutrient application for both macro and micro nutrients, and increased profitability due to higher crop yields and fewer trips across a field when compared to dry granular fertilizers.

Liquid fertilizers offer unique advantages over dry granular fertilizers.

Graphic of two corn kernels.

Liquid Suspension Fertilizers – Unique Advantages at Affordable Costs

Liquid suspension fertilizers provide the same agronomic and economic advantages as clear liquids (starter fertilizer, foliar sprays, those used in drip tape or over the top irrigation systems), but are more reasonably priced than clear liquids.

How can this be?

FIRST: the phosphoric acid used to make the phosphorus fertilizer source in liquid suspensions takes fewer manufacturing/processing steps than the phosphoric acid used to make starter fertilizer-grade clear liquids.

SECOND: in liquid suspensions, a small amount of clay is used to keep fertilizers suspended in a liquid solution. This is particularly important for the potassium source used to make liquid suspension fertilizers.

For example, without the added clay, only about 1 lb of potassium chloride could be dissolved in 1 gallon of water, but with the addition of a small amount of clay, that same 1 gallon of water can hold about 3 lbs of potassium chloride. Liquid suspensions are higher analysis fertilizers (higher % plant nutrients per/gallon material), which reduces transportation costs. When lower transportation cost are paired with more cost-effective raw materials, liquid suspensions can be priced lower than clear liquids, and are cost-competitive with dry granular phosphorus and potassium fertilizers.

Three-panel graphic of corn plant spreading roots into fertilized areas of the soil
Figure 1
Fertilizer Source N-P-K-S-ZN-B Rate lb/ac Yield bu/ac Fertilizer Cost $/ac Net Return $/ac
Liquid Dribble Band 21-50-75-15-0.5-0.2 231.2 47.1 +16.7 $/ac Liquic
Dry Broadcast 227 44.8 Dribble Band

Table 1

Banding Liquid Suspensions for Increased Fertilizer Nutrient Uptake and Crop Yields

Bar graph showing 3% increase in soybeans and 12% more in corn.
Figure 2. Nutrient uptake changes from banding vs broadcasting equivalent rates of ammoniated phosphorus fertilizers. Adapted from Nkebiwe, et al., 2016.

Besides being cost-effective, liquid suspensions are extremely easy to surface or subsurface band.

Banding nutrients achieves two goals: reduced phosphorus fertilizer fixation with Ca2+, Al3+, and Fe3+, and roots become highly concentrated in nutrient-rich fertilizer bands (figure 1). As a result of reduced phosphorous fertilizer fixation (tied up in non-plant-available forms) and increased root activity in nutrient-rich fertilizer bands, the amount of applied fertilizer that is taken up by both corn and soybean crops is increased. In fact, a group of crop scientist recently organized 39 science-based studies with the objective of comparing the effects of banding vs broadcasting fertilizer phosphorus on nutrient uptake and crop yields (Nkebiwe et al. 2016). Averaged over 112 comparisons of banded vs broadcasted phosphorus fertilizer sources, they found that banding phosphorus fertilizer increased nutrient uptake by 12% (figure 2) and corn yields by 4.5% (9 bu/ac or $31/ac at 200 bu/ac yield level) compared to broadcasting the phosphorus fertilizer sources.

Fertilizer Applications—Advantages and Disadvantages

Graphic of a corn plant subjected to broadcast fertilizer

Dry Broadcasting


  • Many acres can be covered rapidly
  • Low application costs


  • Application uniformity is poor and can result in reduced crop yields
  • Broadcasting results in fertilizer fixation in the soil and lower crop nutrient uptake when compared to banding fertilizer
  • Blended dry fertilizers sift or segregate during transportation and handling which can lead to lower or higher fertilizer applications rates than intended
Graphic of a corn plant subjected to subsoild band-applied fertilizer

Subsurface Banding


  • Application uniformity is very consistent
  • Replenishes subsoil plant nutrients
  • Banding reduces fertilizer fixation in the soil, increases root activity in nutrient rich bands, and leads to higher nutrient uptake and often higher grain yields
  • During dry weather, subsurface placed nutrients remain more plant-available than fertilizer nutrients placed on the soil surface
  • Eliminates the chance for fertilizer runoff during high intensity rainfall events


  • 3 to 5 times slower than broadcasting or dribble banding fertilizer nutrients
  • Slower application increases labor costs
  • Initial investment in high horsepower tractors and subsurface placement implements can be high
  • Yield increases when compared to broadcasting or dribble banding fertilizer may not always be high enough to cover added labor and equipment costs
Graphic of a corn plant subjected to dribble band-applied fertilizer

Dribble Banding


  • Many acres can be covered rapidly
  • Application uniformity is consistent for each plant
  • Banding reduces fertilizer fixation in the soil, increases root activity in nutrient rich bands, and leads to higher nutrient uptake and often higher grain yields
  • Low application costs


  • Floaters equipped with high capacity pumps and oversized hoses are needed to apply liquid suspension fertilizers

Liqui-Grow's Local On-farm Research – 2016 & 2017 Results

For the last two crop seasons (2016 & 2017), we have partnered locally with growers to compare what effects broadcasting dry granular fertilizers vs surface dribble banding liquid suspensions fertilizers has had on corn yields. These studies were on-farm strip trials set up as valid experiments with randomized treatments and multiple replications. The dry fertilizers and liquid suspension fertilizers were applied at the same plant nutrient rates per acre. These trials were located in Traer Iowa, Morning Sun Iowa, Washington Iowa, and Roseville Illinois.

In 74% of the side-by-side comparisons, surface-banded liquid suspension fertilizers produced more corn grain than equivalent rates of dry broadcasted granular fertilizers.

We applied the fertilizer, and the farmer cooperator harvested the plots with their commercial combines.

In 74% of the side-by-side comparisons, surface-banded liquid suspension fertilizers produced more corn grain than equivalent rates of dry broadcasted granular fertilizers (figure 3). Moreover, in 68% of those side-by-side comparisons, net returns were higher for the liquid suspension fertilizers (figure 4). Overall we found that yields were increased by 2% (4.2 (bu/ac) and profit per acre was increased by $16.7/ac from banding vs broadcasting fertilizer nutrients (table 1). Our findings are similar to those recently summarized by Nkebiwe et al. 2016, and are yet another example of what effects banding has on fertilizer nutrient availability, crop nutrient uptake, and grain yields.

Banded liquid suspension yield increased graph
Figure 3. Yield increase from using banded liquid suspension fertlizers vs brodcasted dry granular fertlizers in 16 side-by-side comparisons.
Banded liquid suspension net return graph
Figure 4. Net return from using banded liquid suspension fertlizers vs brodcasted dry granular fertlizers in 16 side-by-side comparisons.


Liquid suspension fertilizers offer unique agronomic and financial advantages. These advantages include accurate fertilizer placement and distribution, macro and micro nutrients that stay blended in solution, and a product that is exceptionally easy to surface or subsurface band apply. These factors together result in reduced fertilizer fixation, increased nutrient availability, and often statistically higher crop yields and net returns than broadcasted granular fertilizers.


Nkebiwe, P.M., M. Weinmann, A. Bar-Tal, and T. Müller. 2016. Fertilizer placement to improve crop nutrient acquisition and yield: A review and meta-analysis.
Field Crops Res. 196:389–401.

Fertilizer Placement Effects Corn Vegetative Development

Liqui-Grow is conducting extensive crop management research in the 2018 growing season in northwest, IL and eastern, IA. This year, we have implemented research at 5 different sites and am conducting 25 different experiments. These experiments include simple corn hybrid evaluations, testing new fertilizer formulations, and extensive studies looking at how bacterial inoculations may interact with various fertilization strategies to name a few. In this short educational video, I review observations we’ve made in a fertilizer placement study located in northwest, IL.

– Dr. Jacob Vossenkemper (Agronomy Research Lead)

Are Bio-fertilizers the Next Frontier in Soil Fertility and Fertilizer Technology?

research tractor in the fieldThat is yet to be determined of course, but we do know that the biological and bio-fertilizers market is estimated to grow from a current market worth of $6.7 billion to $12.9 billion by the year 2022. What’s this mean if I am a farmer? A rapidly growing biological market aimed at the agricultural sector means farmers need to become educated about what biologicals and bio-fertilizers may and may not be able to offer them. Over the last 4 months or so I have been browsing the scientific literature educating myself about what we do and do not know about these bio-fertilizers. I have learned that due to advancements in genome sequencing it is now much easier, faster and cheaper to identify and isolate specific bacterial and fungal strains that do in-fact provide services that can improve plant growth and yield.

Some of the agronomically important services bio-fertilizers may be able to provide include: atmospheric nitrogen fixation for cereal crops (corn, wheat, etc..), bacteria that are able to convert non-plant available forms of soil nutrients into plant available forms (phosphorus and potassium solubilizing bacteria), bacteria that can compete with plant pathogenic fungi and other harmful bacteria, and specific strains of bacteria have been shown to produce plant growth regulators (Indole acetic acid and gibberellic acids) that can stimulate root growth and development. See the bulleted list below for more specific details about what bio-fertilizers have been shown to be able to achieve is science-based studies.

Bio-Fertilizers 2018 Field Testing

Tractor in Field for Bio Fertilizer

The unfortunate part is that many of these known benefits of bio-fertilizers have been tested more often under greenhouse vs. actual field conditions. That said, there is an increasing amount of evidence that these bio-fertilizers may, in fact, be able to increase corn and soybean yields in actual field environments, but our knowledge in actual field conditions is clearly more limited than what has been shown in greenhouse studies. On this note, Liqui-Grow has partnered with several biological companies that are leaders in the bio-fertilizer market. We will be testing their most promising bio-fertilizer products at several locations throughout eastern, IA and northwest, IL in the 2018 growing season. My main objective at Liqui-Grow is to identify and investigate (in-formal field research trials) new and innovative products and crop management practices that can make our customers and our company more profitable – partner with us to find out what we learn.

Known Agronomically Important Services Bio-fertilizers Can ProvideBacteria

  • Nitrogen-fixing bacteria can add 25-45 lbs N/ac/yr (Azospirillum, Azotobacter) under optimum soil conditions and thereby can increase crop yields 15-25%.
  • Application of bio-fertilizers results in increased mineral and water uptake, root development, and vegetative growth.
  • Some bio-fertilizers (eg, Rhizobium BGA, Azotobacter sp) stimulate the production of growth promoting substance like vitamin-B complex, Indole acetic acid (IAA) and Gibberellic acids.
  • Phosphate mobilizing or phosphorus solubilizing bio-fertilizers/microorganisms (bacteria, fungi, mycorrhiza etc.) converts insoluble soil phosphate into soluble forms by secreting several organic acids and under optimum conditions, they can solubilize/mobilize about 30-55 lbs P2O5/ac due to which crop yield may increase by 10-20%.
  • Bio-fertilizers act as antagonists/competitors and suppress the incidence of soil-borne plant pathogens and thus, help in the bio-control of diseases.
  • Nitrogen-fixing, phosphate mobilizing and cellulolytic microorganisms in bio-fertilizer enhance the availability of plant nutrients in the soil and thus, sustain agricultural production and farming system.
  • Bio-fertilizers are a cheap, pollution free and renewable energy sources.
  • Bio-fertilizers improve physical properties of soil, soil tilth and soil health in general.
  • Blue-green algae like Nostoc, Anabaena, and Scytonema are often employed in the reclamation of alkaline soils.
  • Bio-inoculants containing cellulolytic and ligninolytic microorganisms enhance the degradation/decomposition of organic matter in the soil, as well as enhance the rate of crop residue decomposition.
  • Azotobacter inoculants when applied to many non-leguminous crop plants, promote seed germination and initial vigor of plants by producing growth promoting substances.

Bio-Fertilizer Services Reference: Agriinfo

Bio-Fertilizers Field Testing

Comparing High Ortho and Conventional Polyphosphate Starter Fertilizers

2017 New Research

High Ortho and Conventional Polyphosphate Starter Fertilizers
Planting starter fertilizer trials near Traer, IA in the growing season of 2016.

Article Summary

  • Orthophosphates are 100% plant available, but a high percentage of polyphosphates in starter fertilizers convert to ortho-phosphate within just two days after application.
  • This quick conversion from poly to orthophosphate suggests expensive “high” ortho starter fertilizers are not likely to result in increased corn yields compared to conventional polyphosphate starters.
  • On-farm field studies conducted near Traer, IA in the 2016 and 2017 growing season found no statistical difference (Pr > 0.05) in corn yield between conventional and high orthophosphate starters in either year.
  • High ortho starters cost more per/ac than conventional polyphosphate starters but do not increase corn grain yields.

Polyphosphates Rapidly Convert to Plant available Orthophosphates

How the Field Trial Was Conducted

Given polyphosphates are not immediately plant available and orthophosphates are immediately plant available, this gives the promoters of “high” orthophosphate starters ample opportunity to muddy the waters. Nevertheless, the facts are, polyphosphates are rather rapidly hydrolyzed (converted to) into orthophosphates once applied to soils, and this hydrolysis process generally takes just 48 hours or so to complete.

In September of 2015, we posted a blog discussing some of the more technical reasons why the ratio of ortho to polyphosphates in starter fertilizers should have no impact on corn yields. For those that are interested in the more technical details, we encourage you to follow this link to the September 2015 blog post.

While we was relatively certain that the ratio of ortho to polyphosphates in liquid starters should have no effect on corn yields, we decided to “test” this idea with on-farm field trials located near Traer, IA in the 2016 and 2017 growing seasons.

How the Field Trial Was Conducted

In these field trials, we used two starters applied in-furrow at 6 gal/ac. Each starter had an NPK nutrient analysis of 6-24-6. The only difference between these two starters was the ratio of ortho to polyphosphates. One of these starters contained 80% orthophosphate and the other contained just 50% orthophosphate. With the remainder of the phosphorus source in each of these two starters being polyphosphate. Each plot was planted with a 24-row planter (Picture 1) and was nearly 2400 ft long. In both the 2016 and 2017 growing seasons the experimental design used was a randomized complete block with 4 or 5 replications.

on farm study near traer iowa 2016
on farm study near traer iowa 2017

Field Trial Results

Averaged over the side-by-side replications there was less than 1 bu/ac difference in corn grain yield between the high ortho and low ortho polyphosphate starters in both the 2016 and 2017 growing seasons. In addition to finding no differences in grain yield between these two starters, the high ortho starters generally cost about $1 more per/gal (so the $6/ac difference in price at a 6 gal/ac rate) than the low ortho starters. So the more expensive high ortho starter clearly did not “pay” its way in our multi-year field trials.

More Trials Planned for 2018

While our findings agree with other research-comparing ortho and polyphosphate starter fertilizers (Frazen and Gerwing. 1997), we want to be absolutely certain that our fertilizer offerings are the most economically viable products on the market. Therefore, we have decided to run this same field trial at one location in northern, IL in 2018, and at one location in central, IA in 2018. Stay tuned for those research results next fall.

Standing in front tractor on Traer, Iowa Farm | Liqui-grow

Want to learn more?

Franzen D. and J. Gerwing. 2007. Effectiveness of using low rates of plant nutrients. North Central regional research publication No. 341. http://www.extension.umn.edu/agriculture/nutrient-management/fertilizer-management/docs/Feb-97-1.pdf (accessed 8 of Sept 2015).

Fall or Spring Nitrogen Fertilizer Sources – Which is More Profitable?

Nitrogen fertilizer is one the most costly crop inputs following seed, and is also quite important for insuring top corn yields. In addition, nitrogen that doesn’t get taken up by a growing corn crop can cause environmental concerns. For these reasons, growers should be concerned with managing this valuable resource carefully. In this educational video Liqui-Grow's agronomy research lead will discuss evidence based research comparing fall vs spring nitrogen sources effects on corn yields and farmer profitability.

Watch on our YouTube Channel

Video Summary

  • Following the 4R’s of nutrient stewardship (the right placement, timing, source and rate) will often lead farmers toward greater crop yields and higher nutrient use efficiency.
  • Applying nitrogen fertilizer for corn production in the spring vs the fall is a great example of the “right” time.
  • Science based studies conducted by the University of Illinois, Minnesota State University and by Iowa State University shows on average a 7.9% yield increase for spring vs fall nitrogen applications
  • Economically these studies clearly show that spring applied nitrogen is the most economical decision for Midwestern corn farmers. In some cases, growers might be able to increase their per acre profit by $43/ac by switching from fall to spring nitrogen sources.

Download the Excel file and use as a tool to plug in your own numbersFall vs Spring Nitrogen Economics

The Nitrogen Grand Challenge

Environmental Stewardship and Liqui-Grow

Environmental Stewardship is essential to what we do at Liqui-Grow. We are extremely committed to helping farmers gain more crop yield per dollar spent on fertilizer while also protecting the environment. Since this is a mission at Liqui-Grow, we’ve decided to take part in the Nitrogen Grand Challenge.

What is the Nitrogen Grand Challenge?

The Nitrogen Grand Challenge, hosted by Tulane University in New Orleans, Louisiana, invites competitors that will provide new and innovative ideas to farmers on managing nitrogen fertilizer for maximum profits and environmental sustainability. The competitors are graded by a formula that incorporates production cost, crop yield, and nitrogen use efficiency; which are all key components of a cost-effective, sustainable nitrogen management program.

There are 3 Phases:

  1. Contestants submit their ideas.
  2. Five best ideas get battle-tested. The five best solutions will go into the ground to see if their idea works on a farm in Northeast Louisiana. They will each get a plot of land to test their specific technology during an entire growing season.
  3. Knockdown drag out fight between two finalists. Judges will determine the winner from the top two contestants.

What is the problem?

“Throughout the world, increasingly fragile coastal and inland lake ecosystems face a common and persistent threat; “dead zones” caused by hypoxia continue to challenge the integrity and productivity of environments that are home to a diverse biota and highly valued natural resources. Dead zones result from excess nutrients flowing from rivers to near-shore areas. Though hypoxia is often thought of as a challenge particular to the northern Gulf of Mexico, dead zones are a problem of global proportions.”

“Hypoxia occurs when the oxygen required to support life becomes depleted, which can result in severe impairment of near-shore fisheries. Consequently, dead zones can also destabilize the businesses, families, and communities that are sustained by fisheries. Further, nutrient enrichment can jeopardize the future of estuaries and coastal wetlands that depend on freshwater and sediment delivery for stability and persistence. In short, clean water is critical to the ecological, cultural and economic well-being of Louisiana, the nation, and the world.”

For more information on the problem, you can visit: http://www2.tulane.edu/tulaneprize/waterprize/the-problem.cfm

Liqui-Grow’s Contributions to the Grand Challenge

Liqui-Grow feels strongly about their customers’ return on fertilizer investment. A high return on every dollar spent on fertilizer often goes hand-in-hand with high nutrient use efficiency and Environmental Stewardship.

As part of our commitment, Liqui-Grow has enlisted their Agronomy Research Lead, Jake Vossenkemper, to participate in the Nitrogen Grand Challenge. Jake is participating on team CropSmith. They have used their innovative ideas on how to manage nitrogen more efficiently to beat hundreds of other teams. They are now competing in the second round of the Nitrogen Grand Challenge against 4 other teams. The winning team will receive a grand prize of one million dollars, but more importantly, they may lead to groundbreaking concepts of nitrogen management that will lead to greater farmer profitability and environmental sustainability.


Fertilizer Placement to Improve Crop Nutrient Acquisition and Yield


  • Fertilizer placement in soil improves plant nutrient-acquisition.
  • Many fertilizer placement techniques have been developed.
  • Fertilizer placement leads to higher yield than broadcast.
  • Fertilizer placement leads to higher plant nutrient-content than broadcast.
  • NH4+ + P or Urea + P placed at 10–20 cm soil depth shows best plant growth effects.

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