Nitrogen Deficiency or Normal Leaf Senescence

Between the R2 and R3 stage, the corn has take up about 75% of the nitrogen for the season. During this time I am often asked “Is my crop running out of nitrogen?”

One common confusion is that many of the symptoms shown in the lower canopy of healthy corn, where there is not a lot of sunlight anymore, falsely resemble a true nitrogen deficiency.

Normal Re-mobilization Nitrogen Deficiency Vs True Nitrogen Deficiency

Even when corn has the optimal nitrogen levels, it’s normal for the very bottom leaves to die off. The corn has out grown those leaves because sunlight cannot reach them anymore. The nitrogen nutrients mobilize and move to the more effective leaves, higher in the canopy.

When taking a closer look, these normal re-mobilization nitrogen deficiencies differ from true nitrogen deficiencies. First, it only effects the very bottom leaves, the next leaf up will be fully green and healthy. Also, you wont see the classic yellow inverted v down the center of the leaf that comes with true nitrogen deficiency. What you will more likely see is just a yellowing on the outside of the leaf that moves it’s way inward.

Armor Spotlight: 0711VT2P/SS

At armor strip trial. To help advance new armor numbers that we potentially bring to market.

One experimental from last year that we are excited to bring to market in 2021 is 0711. It’s had a stellar and consistent performance.

Last year we not only ran the 0711 hybrid through strip trials but also through the first independent seed testing trials. It excelled in both.
In the first trials, located in southern WI and Norther IL, it placed 2nd among 66 hybrids. In the independent first trials located in central Iowa it placed 11th out of 54 hybrids.

From all the trials it has averaged in the top ten hybrids. Besides being reliable, it has shown excellent standability, and it comes out of the ground well.

Stalk Lodging in Potassium Deficient Corn

In July we had over 60 mph winds at our Walcott Iowa research farm and I noticed some stalk lodging.

As you may know, corn with lower than optimal potassium levels, yield less grain. On top of that, potassium deficiency also reduces stalk strength, causing both root and stalk lodging.


Decision Drivers for Foliar Fungicide Application

With the weather forecast in the 90s for July, the most significant disease expected is Grey Leaf Spot. When deciding whether or not to apply fungicide, the gut reaction tends to be based on corn prices. Yes the price of corn has an impact on the profitability of apply fungicide, but there are other decision drivers to consider.

You should consider these big time drivers for fungicide response:

Crop Rotation – If you are on corn after corn, expect a much higher response to fungicide than normal
Tillage Method -Reduced-till, no-till or strip-till create higher amounts of residue that can harbor diseases.

Another helpful tip is understanding the hybrid’s response to fungicide application. We have a great partnership with WinField United and they do several tests comparing hybrids with and without fungicide application. This helps us inform you of the genetic predispositions of various hybrids and their response to foliar fungicide.

If you have any questions, please contact us. We are here to help.


Dekalb 61-40/41 Product Spotlight

The DKC 61-40/41 is a valley girl. She is high maintenance but brings the yield! The hybrid features high drought and heat tolerance, but doesn’t handle water as well. Place it on well drained acres. The roots are narrow and penetrating. Keep the population moderate to prevent the roots mass from dwindling and getting “tippy”.


Corn on Corn Management

photo of rows of corn for decorative purpose


Dr. Brad Bernhard discusses the key management factors needed to overcome the yield penalty when planting corn on corn.


  • Residue Management
    • bury or size the residue


  • Nitrogen Management
    • keep nitrogen fertilizer and residue apart


  • Starter Fertilizer
    • helps plants overcome early season nutrient deficiencies


  • Field Selection
    • select high yielding fields


  • Foliar Fungicides
    • disease protection


  • Hybrid Selectionge
    • stress emergence, yield stability, and disease package

Agronomy Research Summary Book 2019

Since the spring of 2015 we have been conducting research on new products and management practices farmers can potentially use to increase both corn and soybean yields and profitability. By now I have amassed a bunch of results that are finalized and ready to share.

These results are now in the form of a book, which contains research on fertilization products and practices, seed treatments for soybeans, fertilizer additives and much more. These research summary books are now available at all of our Liqui-Grow locations. You can also download the PDF or request a book by calling the main office (563-359-3624) or email Tammie Suhl at

We plan to print updated books every year to keep you well informed.

photo of Dr. Jake Vossenkemper
Dr. Jake Vossenkemper
Agronomy Research Lead

Managing for Higher Corn Plant Populations

photo of rows of corn for decorative purpose

Article Summary

  • Higher plant populations can be managed by planting in narrower row spacings.
  • As plant population increases, the size of each individual root system becomes significantly smaller, which increases the need for better crop management especially fertility.
  • When growing corn at higher plant populations and/or narrower row spacings, it is important to select a hybrid that has a positive yield-response to these more intensive management practices.

Corn yields have increased significantly since the 1930s largely due to genetic improvement and better crop management. Grain yield is the product of the number of plants per acre, kernels per plant, and weight per kernel. Of the three components that make up grain yield, the number of plants per acre is the factor that the grower has the most direct control over. Kernel number and kernel weight can be managed indirectly through proper fertility, weed, pest and disease management to optimize plant health, and weather also plays a major role. Currently the average U.S. corn planting population is just under 32,000 plants per acre and has increased 400 plants per acre per year since the 1960s. If this trend continues, the average U.S. corn planting population will reach 38,000 plants per acre in 15 years and 44,000 plants per acre in 30 years.

Narrower Row Spacings

Today, the vast majority of corn in the U.S. is planted in 30” row spacings, with narrower rows generally defined as any row spacing or configuration less than 30” row spacings.

The most common narrower row spacings include 20” and 15” rows, along with twin rows that are spaced 7.5” apart (22.5” between rows, but are on 30” centers). Narrower row spacings can be used to increase plant-to-plant spacing within a row to reduce crowding at higher plant populations, thereby, allowing the crop to better utilize available light, water, and nutrients
(Figure 1).

In 2017 and 2018, six commercial DeKalb hybrids were planted at 38,000, 44,000, 50,000, 56,000 plants per acre in a 30” and 20” row spacing at Yorkville and Champaign, IL.

30 inch rows of corn and 20 inch rows of corn

Figure 1. At the same plant population of 44,000 plants per acre, greater plant-to-plant spacing is achieved in the 20” row spacing compared to the 30” row spacing.

The management system that resulted in the highest grain yield of 294 bushels per acre was planting 44,000 plants per acre in a 20” row spacing (Table 1). The minimum plant population that maximized grain yield in a 30” row spacing was 38,000 plants per acre. On average, across plant population, plants in a 20” row spacing yielded 12 bushels per acre more than when planted in a 30” row spacing, however, as plant population increased the yield advantage of the 20” rows over the 30” row spacing was greater. Planting 56,000 plants per acre at either row spacing was too high of a population and yield decreased without a sufficient amount of resources such as water or nutrients to support that many plants. Evidence suggests that there is a limit on how high planting population can be pushed in either a 30” or 20” row spacing without any additional fertilizer, crop protection, or irrigation.

Better Crop Management

Management systems that decreased plant-to-plant spacing within a row, such as wider row spacing and higher plant population, decreased the size of the root system. On average, for every additional 6,000 plants planted per acre there was a 15-18% decrease in the size of the root system (Figure 2). However, when planted in a 20” row spacing, the greater plant-to-plant spacing increased the size of the root system by 22%. At higher plant populations, not only are there more plants that require nutrients and water, but each of those plants also have a significantly smaller root system. Crop fertility becomes even more important under these more intensive growing conditions. Placing nutrients directly in the root zone at the right time using the correct source and rate increases the probability that roots will take up and utilize those nutrients.

For every additional 6,000 plants planted per acre there was a 15-18% decrease in the size of the root system.

Comparison of corn roots based on 20 and 30 inch row spacing

Figure 2. Individual plant root size decreases as plant population increases. At a given plant population, the 20” row spacing has a larger root system compared to the 30” root system.

Select the Right Hybrid

Hybrids vary greatly in their response to plant population and to narrower row spacings (Table 2). Hybrids also vary in their plant architecture and leaf trait characteristics. Understanding which hybrids better tolerate higher plant populations and narrower row spacings along with the plant growth and leaf traits that these hybrids possess would help lead the breeding effort for selecting hybrids that will perform even better in these management systems. Hybrids that produced greater yields in response to narrower row spacings and higher plant populations tended to possess the following plant growth and leaf traits: 1) greater above-ground biomass, 2) high leaf area index, 3) upright leaves, 4) thin leaves, and 5) less leafy plants.

Table 1. Grain yield as influenced by plant population and row spacing for corn averaged across six corn hybrids grown at Yorkville and Champaign, IL in 2017 and 2018.

table comparison of yields based on plants per acre and the row spacing

Table 2. Grain yield and profit difference between planting 38,000 plants per acre in a 30” row spacing compared to 44,000 plants per acre in a 20” row spacing for six DeKalb corn hybrids grown at Yorkville and Champaign, IL in 2017 and 2018. Profit was calculated using $3.50 corn and $320.00 per bag of corn seed.

Table with hybrid comparisons


As the trend of increasing planting populations continues, it is important to consider the effects that the reduced plant-to-plant spacing has on the corn plants. Crop management becomes even more important, especially fertility, under these crowded conditions. Narrower row spacings can be used as a tool to reduce the plant-to-plant competition at higher planting populations.

Focus Seed Catalog

Header image for Seed Catalog

Photo of hand holding a seed

Focus: the center of activity, attraction, or attention.


That’s what we are committed to do. We know not every hybrid fits every acre or management style but here are the hybrids we are excited to use in 2020.





   PDF File Download



   Dekalb Corn Hybrids

   Mycogen Corn Hybrids


   Armor Corn Hybrids

   Mycogen Soybean Hybrids

   Asgrow Soybean Hybrids

   Armor Soybean Hybrids

   PDF File Download

New Research Comparing Ortho/Poly-Phosphate Ratios


Blog Banner for Poly Phosphate study


  • Ortho-phosphates are 100% plant available, but a high percentage of poly-phosphates in starter fertilizers convert to ortho-phosphate within just two days after application.
  • This quick conversion from poly to ortho-phosphate suggests expensive “high” ortho starter fertilizers are not likely to result in increased corn yields compared to conventional poly-phosphate starters.
  • On-farm field studies conducted near Traer, IA and Walnut, IL from the 2016 to 2018 growing season found no statistical difference (Pr > 0.05) in corn yield between conventional and high ortho-phosphate starters.
  • High ortho starters cost more per/ac than conventional poly-phosphate starters, but do not increase corn grain yields.

Poly-phosphates Rapidly Convert to Plant available Ortho-Phosphates

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

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

While we were relatively certain that the ratio of ortho to poly-phosphates in liquid starters should have no effect
on corn yields, I decide to “test” this idea with on-farm field trials located near Traer, IA and Walnut, IL  in the 2016, 2017 and 2018 growing seasons.

tractor planting fertilizer

Picture 1. Planting starter fertilizer trials near Traer, IA in the growing season of 2016.


How the Field Trial Was Conducted

In these field trials we used two starters applied in-furrow at 6 gal/ac. Each starter had a NPK nutrient analysis of 6-24-6. The only difference between these two starters was the ratio of ortho to poly-phosphates. One of these starters contained 80% ortho-phosphate and the other contained just 50% ortho-phosphate. With the remainder of the phosphorous source in each of these two starters being poly-phosphate. At the Traer, IA locations the plots were planted with a 24-row planter (picture 1) and were nearly 2400ft long. At the walnut, IL locations the research was conducted using small plot techniques, plot dimensions there were 10 ft wide by 30 ft long. At both Traer, IA and Walnut, IL in each of the 3 growing season the experimental design used was a simple randomized complete block with 4 or 5 replications.

Figure 1. Average corn yield from field trials comparing high ortho vs conventional poly-phosphate in-furrow seed safe starter fertilizers. Yields at each location/year are averaged over 4 or 5 replications.


Figure 2. Partial profit from field trials comparing high ortho vs conventional poly-phosphate in-furrow seed safe starter fertilizers. Yields at each location/year are averaged over 4 or 5 replications. Partial profit was calculated using a grain sale price of 3.50 bu. Cost per gal used to calculate partial profit for the 6-24-6 50% ortho & 50% poly-phosphate and 6-24-6 80% ortho & 20% poly-phosphate was $2.80 and 3.20 per/gal


Field Trial Results

Averaged over the 5 site-years there was only about 1.5 bu/ac yield difference separating the high ortho and conventional poly-phosphate starter (figure 1). Moreover, this small yield difference was not statistically significant (Pr > 0.05). In addition to finding no differences in grain yield between these two starters, the high ortho starter cost about $0.50 more per/gal (so $3/ac difference in price at a 6 gal/ac rate) than the lower ortho starters. So the more expensive high ortho starter clearly did not “pay” its way in our multi-location field trials (figure 2). Lastly, our observations in these studies agree with previously published university findings (Frazen and Gerwing. 1997).


Franzen D. and J. Gerwing. 2007. Effectiveness of using low rates of plant nutrients. North Central regional research publication No. 341. (accessed 8 of Sept 2015).


– Dr. Jacob Vossenkemper (Agronomy Research Lead)