Jake Vossenkemper

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.


Generic Vs Branded Fungicide for Soybeans

One factor at our intensive soybean management trial is a Fungicide/ Insecticide application at R3. This is one of the more consistent measurement factors that you can implement on your farm to increase yield and ROI.

Generic Vs Branded
I understand farmers want to save a few bucks with the generic fungicide. However, that tech was built in the 70s and 80s. Newer fungicides have longer residual, more systemic and multiple modes of action, making them a more reliable investment. In my research and field experience, the extra yield you will receive from branded fungicides exceeds the added cost.


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.


How to Spot Potassium Deficiency in Soybeans

Potassium deficiency in soybean plants can be confusing. Typically in corn we see signs of deficiency worst at the bottom of the plant. This is because the nutrient is very mobile and potassium will prioritize leaves at the top of the plant. However, in soybeans, we often see the deficiency towards the middle to top of the plant with yellowing edges and necrotic leaf margins, while lower leaves can remain healthy and green.

Effects of recent cold rain on corn seedling viability and stand establishment

This morning I am getting lots of questions about what impact yesterday’s cold rain had on corn stand establishment. The short answer is the cold rain likely had very little impact on seed viability or final stands. For a further explanation, I would like to point you to a very well done video explanation by our new DeKalb Technical Agronomist, Nicole Stecklein. She is very knowledgable in agronomy and I encourage you to get to know her after meetings and other co-sponsored Liqui-Grow/DeKalb events.

Late Planting & Fall Killing Frost Concerns

The 2019 growing season has been anything but “normal” thus far. We have had well above normal precipitation, below normal heat unit accumulation and delayed planting. Moreover, the extended 3 month forecast published by NOAA and the National Weather Service calls for higher than normal probabilities of precipitation and lower than normal temperature probabilities thorough out the remainder of the summer (figures 1 & 2).

3 month outlook of precipitation probability for the continental USA
Figure 1. NOAA 3 month precipitation outlook
3 month outlook o3 month outlook temperature  probability for the continental USA
Figure 2. NOAA 3 month temperature outlook.

These facts have resulted in many sales agronomist and growers wondering if the crop will make it to black layer (maturity) prior to a killing frost? To help answer these questions I have used a decision support weather model/tool developed by the Midwest Climate Center and their affiliates to help derive some insights into this question.

To help answer this question I plugged in 3 hypothetical planting dates (May 25th, June 5th and June 15th) into the U2U weather/GDD model, and three different maturities spanning early to full maturity corn hybrids. I also ran the U2U weather tool at 4 different latitudes. A latitude approximating Roseville, IL, Davenport, IA, Clear Lake/Hampton, IA and Elkhorn, WI. While I won’t take the time to carve through all the graphs and data, I will give a brief synopsis of my findings.

Fun fact, the definition of a killing frost is when temperatures reach 28 degrees F or colder. This temperature is usually cold enough to turn water within plant cells into ice crystals. These expanding ice crystals burst cells and are usually lethal to the entire plant. Hence “killing frost”.

Roseville, IL & Davenport, IA Latitudes

In general I found that hybrids ranging from 104 RM to 114 RM have a high probability of making it to black layer prior to a killing frost at the Roseville, IL and Davenport, IA latitudes (figure 3 & 4) when planted by May 25th or earlier planting dates. For hybrids planted on June 5th, it looks like the 104 to 110 day RM hybrids will also have a good chance of making it to black layer prior to a killing frost, but very full hybrids (113 to 114 RM) may experience a killing frost prior to black layer at these latitudes (figure 3 & 4). Any hybrid (104 to 114 RM) planted on or after June 15th at the Roseville, IL and Davenport, IA latitudes has a 50% chance or greater probability of experiencing a killing frost prior to black layer.

Graph to show percent change of killing frost
Figure 3: The % chance of corn hybrids reaching black layer prior to a killing frost for 3 hypothetical planting dates at latitudes close to Roseville, IL, Mt Pleasant, IA & Morning Sun, IA.
Graph to show percent change of killing frost
Figure 4: The % chance of corn hybrids reaching black layer prior to a killing frost for 3 hypothetical planting dates at latitudes close to Davenport, IA.

Clear Lake & Hampton, IA & Elkhorn, WI Latitude

For the latitude’s close to Elkhorn, WI any mid and short-season hybrids (95 to 101) planted on or before May 25th have a greater than 50% chance of making in to black layer prior to a killing frost, but full maturity hybrids (107) even when planted on May 25th have a poor chance of making it to black layer prior to a killing frost (figure 6). If corn was planted on June 5th only the short-season hybrids (95) hybrids have a good chance of making it to black layer before a killing frost at this latitude (figure 6). For regions close to this latitude all RM hybrids (95 to 107) planted on or after June 15th don’t seem to have a good chance of making it to black layer if we have a normal frost date (Oct 18th) for this region. But most full-season hybrids at this latitude are grown for silage, so a killing frost is likely not to be a concern for those silage acres given harvest is much sooner than when harvesting for grain.

Graph to show percent change of killing frost
Figure 5: The % chance of corn hybrids reaching black layer prior to a killing frost for 3 hypothetical planting dates at latitudes close to Clear Lake and Hampton, IA.
Graph to show percent change of killing frost
Figure 6: The % chance of corn hybrids reaching black layer prior to a killing frost for 3 hypothetical planting dates at latitudes close to Elkhorn, WI.

The Good News

While a killing frost sounds devastating to yield, a killing frost when grain yield is still rapidly accumulating during mid and early reproductive growth/development is rare. The more likely scenario is that we may experience a killing frost very late in the grain filling period (also known as reproductive growth period). A killing frost at 35 to 40% kernel moisture usually has negligible effects on grain yield, given all yield has nearly been accumulated. A rarer scenario is that we could experience a killing frost at half milk line, this could result in more severe yield losses, (10 to 15% range), slower field drying, difficulty shelling kernels from cobs and poor test weight. The best scenario for us all would be a warm dry fall.

2019 Nitrogen Loss and Recommendations

How to Correct the Nitrogen Loss

Nitrogen loss will be a big concern in 2019 given all the wet weather. As such and for good reason, there have been many questions regarding how much N may have been lost and what we can do to go about correcting these N loss problems. To address these concerns and questions I have made a video discussing these various issues. As you will learn in this video I will produce a second video with PSNT soil test results and nitrogen model estimations of N loss which may refine my initial thoughts and recommendations. 2019 is off to a rough start, but the more in-the-know you are, the better your yield.

  1. If you had more than 10 inches of rain since N was applied its advised that you recommend applying more. Nitrate soil tests are confirming this.
  2. N models don’t seem to be aligning very well with the nitrate nitrogen tests that I took and some general knowledge about what we know regarding rain fall amounts and precipitation.

Bottom line, N models may be valuable, but they don’t replace good sound experience and agronomic advise. Follow recommendations from N models with caution.


– Dr. Jacob Vossenkemper (Agronomy Research Lead)

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 (liqui-grow.com/farm-journal).

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. http://www.extension.umn.edu/agriculture/nutrient-management/fertilizer-management/docs/Feb-97-1.pdf (accessed 8 of Sept 2015).


– Dr. Jacob Vossenkemper (Agronomy Research Lead)