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Weakly Buffered Soils

When adding lime to acidic soils to increase the soil pH, the lime needs to neutralize the acidity in the soil solution along with the acidity released from the soil’s CEC in the process. There is a pool of reserve of acidity on the soil CEC that is released to maintain equilibrium between the CEC and soil solution. The impact of this reserve acidity held by the cation exchange sites will vary depending on the CEC of the soil.

The rate of lime to apply in the goal of neutralizing acidity is determined by using the buffer pH for soils with a CEC above 7, and organic matter below 20%. The buffer pH is a measurement of all acidity in the soil solution along with the reserve acidity held by the CEC of the soil. As soil CEC decreases so does the pool of reserve acidity. Below a CEC of 7 the reserve acidity is small and has little impact on lowering the buffer pH. Therefore, buffer pH is not a good indicator of lime application rate for these soils.

For weakly buffered soils, lime is applied at 1 ton/acre for each 0.3 - 0.4 of desired increase in soil pH, maximum 2 ton/acre. pH adjustments are usually triggered when the soil pH is 0.3 units lower than the target pH for the field.

A weakly buffered soil can have a CEC in high 6’s to low 7’s. To determine if a soil is weakly buffered, calculate lime rate for soils with a water pH of 6.2 or below using the weakly buffered rate above and an equation using buffer pH, use the higher of the two calculated lime rates. For more information on weakly buffered soil, contact you regional ALGL sales agronomist. 

Different Sources of Phosphorus

To determine the right source of phosphorus, there are several factors that need to be taken into consideration.  First, a background of this macro-nutrient and how it is utilized in the plant.  Phosphorus, or P on the periodic table, has various states in soil.  It can be fixed, active and/or part of the soil solution.  Fixed P is the largest of pools and is not available to the plant.  The conversion of fixed to active is very slow and has little impact on soil fertility.  Active P in solid phase can be released into soil solution easily and replenishes the soil solution as the plant removes.  Phosphorus in a soluble state, or solution, is the only form for plant uptake. 

The role of phosphorus in the plant starts with being the elemental component of ATP-ADP, DNA and RNA.  These are the energy sources for photosynthesis, and transfer energy/nutrients. P plays an important role in fruit set/development and an essential component of cell membranes. 

Manure and biosolids can supply large amounts of P and is usually a direct reflection of their diet.  Before applying these sources, a laboratory analysis must be conducted for proper rates.  Handling, storing and transport of manure sources can be challenging.  This usually creates more inconsistencies from one sample to another.  There are, however, several commercial fertilizer options that are consistent.

Monoammonium Phosphate (MAP; 11-52-0) is water soluble and makes the pH surrounding the granule reasonably acidic at 4-4.5 pH.  This makes MAP one of the more suitable fertilizers in neutral to high pH soils. 

Diammonium Phosphate (DAP; 18-46-0) is one of the most used P fertilizers in North America.  It has a high nutrient content and is easy to handle/store.  Unlike MAP, an alkaline pH of 7.5-8 is formed around the granule.  Ammonium is released from the fertilizer and becomes volatile.  This is only a concern if placed too close to germinating seeds, is not incorporated, or pH is higher than 7.  As bacteria convert the nitrogen to nitrate, the pH is lowered.

Ammonium Polyphosphate (APP; 10-34-0 or 11-37-0) is comprised of orthophosphate and polyphosphate.  50-75% of the P is in the form of polyphosphate.  This makes the other 50-25% readily available for plant uptake.  What is not readily available, will eventually convert to available in a short period of time depending on the environment. 

Triple Superphosphate (TSP; 0-45-0) has one of the highest P concentrations out of all the fertilizers not containing nitrogen.  Over 90% of the total P is water soluble, making it a good choice for fast plant uptake.  This fertilizer will make the soil solution acidic (pH 2-3) as the granule dissolves.  It is a great choice for blending custom applications.

There are several options for phosphorus fertilizers on the market, and these are just a few of the commercial ones available.  When deciding which one to utilize, always apply based on soil test data, and be mindful of the 4Rs (Right Source, Right Rate, Right Time and Right Place). 

Reference: International Plant Nutrition Institute. (2012). 4R Plant Nutrition: A manual for improving the management of plant nutrition (pp. 40-41). Norcross, GA, USA: International Plant Nutrition Institute

Fall Lawn Aeration

Recently the greater Midwest region has been experiencing drought conditions.  This has not made it easy for lawncare, or annual maintenance, that is usually conducted in the fall.  One positive experience when undergoing times of environmental stress is the possibility to see flaws that are usually covered up, or otherwise hidden.  This is a perfect time to access situations like compaction, low grass densities or poor root growth in yards. 

Once a lawn is established, it makes alterations or “fixing” issues very difficult and time consuming.  The good news is that with the right tools, knowledge and some patience most issues if not all can be resolved.  When scouting a lawn during drought conditions the easiest, and most noticeable, concerns will be the different colors.  What makes turf brown, green or a shade in-between starts with the question, why?  Usually, the weeds will still stay green during times of stress, and the grass will go dormant.  This causes large patches to turn brown and if uniform potentially the whole yard. 

This is when the caretaker will notice the sins of the past as well.  There will be brown, or yellow, areas caused by compaction or poor drainage.  This is from the grass not having a vigorous root system due to poor porosity in the soil, or potentially a hardpan from topsoil being brought in then dumped on hard clays during the construction of structures.  High traffic areas will also show signs of abuse as soil moisture declines. 

Compacted areas are difficult to manage in established lawns, however, depending on how deep the compaction is, it can be amended.  For the Midwest, the freezing and thawing over the winter months helps.  If it is surface or shallow compaction, using a core aerator will promote better root development over time and help increase the amount of air in the soil.  There are several different turf aerator types on the market.  Using a ride-on, hydraulic core aerator will be the best option for depth and getting the largest core size especially during drought conditions.

More than likely, this will not be a one-season fix.   Depending on soil type, grass species and severity, it may take several seasons.  The core aerator will promote soil contact with the surface of the grass.  This helps with the breakdown of thatch.  Thatch is a layer of dead grass located on the soil surface.  It is when grass accumulates faster than decomposed.

Once the lawn has been aerated, this is a perfect time to overseed, fertilize and adjust pH if necessary.  Some of the larger aeration tools allow a 5” core to be pulled.  This enables a perfect area for pH buffering materials to enter a lower profile.  Soil is then exposed, creating better seed to soil contact and fertilizing, for example nitrogen, will promote the breakdown of the season’s thatch as well. 

Looking Back to 2012

It is hard to predict the impact of the current dry fall on soil sample results. Only after the sampling season is over can we determine if the dry weather impacted soil test results.  What we can do is look back at previous years and learn from experience.

Soil pH is impacted by an increase in soluble salts in the soil solution that haven’t leached downward through the soil profile during a prolonged severe drought. The soluble salts do not actually change the pH, rather it interacts with the soil pH probes there at the lab leading to the lower reading. Given that the drought set in for most of the ALGL service area later in the year after crop establishment. In our cropping systems the main salt inputs are fertilizers and manures. The salt from application in the fall of 2023 should have leached out of the sampling zone over the winter. While spring rain was not heavy in most areas, there was enough to leach most of the soluble salts resulting from spring 2024 applications from the soil. A simple reference is that when tiles are flowing water, water is infiltrating down through the soil profile and taking soluble salts with it.  

For comparison this year is much like 2012 for many areas. During a severe drought, water pH readings may be 0.1 to 0.6 pH units lower than expected. Looking back, pH data from 2012 does not stand out in the long-term data and indicates that the drought did not significantly impact soil pH in 2012.When soils remain extremely dry for extended periods of time, the space between the layers of shrink-swell clays, those that form large crack in dry conditions, gets smaller. This traps potassium between the clays layers that prevents the inner clay layer potassium from replenishing the available potassium in the soil solution as it is diminished through crop uptake. This can show up as a reduction in the soil test level. Also, potassium is easily leached from crop tissue following harvest. With little rainfall, this potassium reserve could remain in/on the crop tissue. One caveat of this, though, is with inadequate moisture to produce normal yields, less potassium may have been taken up by the crop. Looking back, potassium data from 2012 is slightly below trend, it does not stand out in the long-term data and indicates that the drought did not significantly impact potassium soil test level in 2012.

2025 Soil Fertility Workshop Dates

Dates and locations are set for the 2025 Soil Fertility Workshops. The goal of our workshops is simple: we provide a general overview of fundamental agronomic principles and current university research so our attendees are better able to make nutrient management decisions for their customers or for their own operations. Today’s producers are inundated with information regarding crop inputs and practices. By applying the fundamental principles of agronomy to these inputs and practices, a consultant, agricultural retailer, or producer can evaluate and decide which of those are most applicable for achieving both the short-term and long-term goals of a specific operation.

The workshops are developed and presented by A&L Great Lakes Laboratories’ Agronomy Staff comprised of Certified Crop Advisers, Certified Professional Agronomists, and Certified Professional Soil Scientists whom have a wide range of experience in the agricultural industry.

We will be presenting six workshops January and February in Illinois, Indiana, Michigan, and Ohio. Registration will open later this year, but mark your calendars today!

January 28, 2025 - Fort Wayne, IN

February 4, 2025 - Champaign, IL

February 12, 2025 - Frankenmuth, MI

February 13, 2025 - Waldo, OH

February 18, 2025 - Grand Rapids, MI

February 20, 2025 - Indianapolis, IN (near the airport)

Introduction of The ALGL Client Portal

We have made our new ALGL Client Portal available to customers. The goal of the ALGL Client Portal is to provide account holders with single sign on access to lab tools you are already using, with new and enhanced tools to make working with us even easier and more convenient.

Current features of the ALGL Client Portal include:

• Access reports and data files with enhanced global search functionality. This is like our existing eDocs system that will remain active through the fall sampling season.
• Print and/or email UPS shipping labels utilizing our RS shipping program.
• Order supplies.
• View and pay invoices online (for authorized users).

Additional features and tools are in development and will be released as they become available.

For more information and to access the ALGL Client Portal Click Here.

Soil Acidification

There are several variables influencing the outcome and production of any ornamental, cash crop or landscape. Weather and environment are the largest of variables, and unfortunately that is just the beginning of obstacles. One inevitable, and often overlooked, variable is soil acidity. Where most have been taught soil acidity is a product of using highly synthetic fertilizers or the result of acid rain there are several contributing factors beyond our control. What is acidity and where does it come from?

Acidity is considered one of the most important variables because it affects several biological and chemical soil properties. Soils with lower pH may even experience a higher fungi population. As a result, acidity can even change the physical properties of soil by promoting air and water movement throughout the soil and stabilize aggregate structures  “Acidity (or alkalinity) is usually quantified using the pH scale, which expresses the activity of concentration of H⁺ ions present in a solution.” (Brady and Weil et al. 2016) Where do hydrogen ions come from?

Carbonic acid is one of the most universal contributors to soil acidity  It is formed when carbon dioxide gas from soil air dissolves in water. This is caused by root respiration and the decomposition of soil organic matter by microorganisms. 

Organic acids are generated as microbes break down soil organic matter through biological metabolism.  These acids can range from citric and malic acids to much stronger types like carboxylic and phenolic groups in humic substances produced by litter breakdown. 

Accumulation of organic matter acidifies the soil for two reasons. During this process, cations are lost by leaching when organic matter forms soluble complexes with nonacid cations. The second is organic matter is a source of H⁺ because it contains many acid functional groups where ions can separate. 

The oxidation of nitrogen, or nitrification, is not solely a consequence of human overapplication.  Nitrogen can be oxidized from organic matter as well as fertilizers. The oxidation reaction produces hydrogen ions as a product which can be a result of bacterial and chemical processes. Two H⁺ ions are released for every NH⁺ ion oxidized.

Acids in precipitation is not always a result of pollution. It is a natural phenomenon and is a variety of acids that contribute hydrogen ions to the soil. As raindrops pass through the air, they dissolve CO² forming carbonic acid. This changes the pH of the water from approximately 7 to about 5.6. Pollution, lightning and natural disasters can contribute to a lower pH precipitation (acid rain). 

Plants must maintain a balance of positive and negative charges they take up from the soil. For every positive charge taken up by the plant it can either take up a negative charge or get rid of a positive charge. If the plant takes too many certain cations, it generally will release H⁺ ions into the soil to maintain balance. 

Soil acidification is inevitable. The good news is many growers can contradict these variables through liming practices. This is why it is always important to soil test and maintain a certain balance for crop/soil health and nutrient availability. 

Source: Brady, N. C., & Weil, R. R. (2016).  The Nature and Properties of Soils (13th ed.). Pearson.

Evaluating Nitrogen Management Late Season

As the 2024 corn crop is approaching maturity throughout the Great Lakes region, many producers and crop consultants are starting to question whether they have applied enough nitrogen to finish out the season. A corn stalk nitrate test (CSNT) can be a useful tool in assessing the effectiveness of a nitrogen program.  However, the test results often generate more questions than answers. Remember, when dealing with a natural system, the word always never applies. The general interpretation of a CSNT is that if the result is less than 700 ppm, nitrogen may have limited your yield, from 700 to 2,000 ppm, nitrogen use was optimal, and greater than 2,000 ppm indicates excess nitrogen. However, the CSNT data cannot be used on its own to make future management decisions. It must be utilized as a part of a more holistic approach including crop observations, soil test data, weather history, fertilizer application history, etc.

When a CSNT shows high levels, the most obvious explanation is that too much fertilizer was applied. No, this does not indicate that growers are carelessly over applying fertilizer. It simply means that for the current growing season, a lower amount of applied nitrogen would likely have generated the same yield for reasons that are impossible to predict at the time the nitrogen was applied. Drought stress is one of the leading causes of high CSNT results. Most growers are applying about 1 pound of nitrogen per bushel of projected yield. So, if 200 pounds of nitrogen is applied between a starter and sidedress application expecting to harvest 180-200 bushels, but a late summer drought cut that yield down to 100-120 bushels, the excess nitrogen will accumulate in the lower stalk since there is not enough grain to utilize the applied nitrogen. Another potential explanation is another nutrient deficiency. For example, if the crop was supplied with enough nitrogen to grow 200 bushels, but the plants are experiencing a severe sulfur or potassium deficiency reducing the yield, there will be excess nitrogen in the plants.

On the contrary, a low CSNT does not always mean that the nitrogen was lost or that more applied nitrogen would have resulted in additional yield. There are situations during unusually good growing seasons and the crop yield exceeds the early season expectations. The plants show no physiological deficiency symptoms and the CSNT shows less than 200 ppm. This indicates that the crop was able to efficiently utilize all the applied nitrogen and additional nitrogen would likely add little to no additional yield.

For more information about collecting CSNT samples and understanding the results, please visit our Cornstalk Nitrate Test Fact Sheet.

Corn Root Architecture and Nutrient Management

There have been many studies over the years documenting nutrient placement, rates, and several types of applications. It is not surprising that these must be conducted repeatedly because there has not been a definite answer to the “how, what and when” questions to nutrient management. In conjunction with nutrition, hybrid selection has also been vigorously evaluated. These studies usually compare offensive and defensive hybrids to certain applications. Is there a better way to portray which hybrid family does well to high fertility, drought conditions or sidedress applications etc.? Jim Schwartz, Beck’s Director of Research, Agronomy and PFR, has partnered with Dr. Fred Below, Professor at the University of Illinois, to understand how different root architectures and sizes affect nutrient management decisions.

The Root Reveal project is a new means of hybrid categorization. Its goal is to place each hybrid type into different root classes. A majority of the seed industry understands different root angles, but few have made the correlation between this and nutrient management on a per-farm basis. When selecting a nitrogen program, how often does the conversation happen discussing which hybrid will perform best with which fertilizer application? The common conversation is which hybrid efficiently uses higher rates of nitrogen or has little to no yield response to excessive amounts.  What Jim Schwartz and Dr. Fred Below are setting out to do is make the conversation, “This is the placement of the fertilizer that will most benefit this hybrid’s root architecture”.

To obtain the root architecture and root volume, each hybrid has been undergoing extensive observation. This has been conducted in several different ways. The first way is a more conventional method. The simple in-field root dig. After the root mass has surfaced, it is then photographed and documented. This, however, is not enough. So, it has been taken one step further by creating a photography chamber for each individual root. The chamber spins at high speeds, taking several pictures, giving a 3D makeup of each hybrid root. Researchers can collect the architecture and root volume of each hybrid root in the matter of a few minutes.

The third way to collect more data on each hybrid root type, is by utilizing Corn Root Boxes.  Beck’s Root Reveal Research is capable of growing an individual corn plant in an empty chemical tote.  “These empty chemical totes were shrink-wrapped, covered with boards, and filled with Turface Athletics™. They were then strung with line to help support and maintain the root architecture of the plant. Each cage contained an individual corn hybrid and was then watered and fed the same amount of nitrogen. Once the plants reached tassel, they were cur off form the water and nutrients and left to dry.” The results show how roots perform without restricting variables of different soil types, compaction, etc.

How will this impact nutrient management? Knowing a certain hybrid has a horizontal or vertical root development directs the grower to better management. Applications, such as nitrogen, are taken into the plant through a process called mass flow. Being an anion allows nitrogen to, mostly, move vertically in the soil profile. If we know where the roots will be, we know where to place the fertilizer. A vertical root system needs to be banded in or near the row. A horizontal root system does well with sidedress applications because it can reach below the application area. For more information visit: https://www.beckshybrids.com/about-us/media/becks-root-reveal-research-digs-deep-into-understanding-corn-root-architecture

Be Wise When Cutting Back on Broadcast Fertilizer

When working with a reduced fertilizer budget, some approaches are wiser than others. When evaluating the approach to take in reducing broadcast fertilizer rates this fall, be sure to ask some questions.

• How will this plan impact the higher yielding areas of the field?
• Is this field already have low fertility and will this reduction have a negative impact?
• How long will/can I follow this plan?
• Should the same approach be used with phosphorus and potassium?
• What is the producer’s tolerance to financial and yield risk?

Before answering these questions, let’s look at the basics of fertilizer recommendations. While there are a wide range of fertilizer recommendations structures, they all have some common fundamentals.

Soil Test Levels – Every fertilizer recommendation structure has a target soil test value that internally will lead to the following categories.

• Below this target value there is a strong probability that crop yield will increase with the application of fertilizer. In these areas, applying a minimum of crop removal of P and K is advisable. This means applying an equivalent amount of P and K to replace the nutrients removed from the field in grain, or forage. Without the financial restrictions, this is the area of the field would possibly receive more fertilizer than crop removal to increase soil test levels. The goal is to prevent soil test levels from declining further and gain any possible yield benefit from the application.
• Above the target soil test level, but below an optimum soil test level, the probability of yield increase from the application of fertilizer is diminished and not expected. If the nutrient is not applied the soil test level could decline below the target level over time. The long-term goal for this category is to apply enough fertilizer to keep the soil test level in this range such as crop removal or slightly less.
• Above the optimum soil test level, there is no benefit to increasing soil test levels any higher. This range of soil test levels receive a fertilizer rate less than crop removal, some fertilizer recommendation structures take this category to a zero application rate. The goal for this soil test range is to not build up or maintain, rather utilize the inventory of nutrients in the soil.
• There is a maximum soil test value where applications need to stop entirely. In most cases the soil reaches a point where it cannot retain all of the applied nutrients, and a notable portion of the nutrients will be subject to environmental loss. For financial and environmental benefit, do not apply nutrients to soils at these levels.

Secondly, we need to look at the behavior of yield in each field. One of two scenarios will develop. When fertility is the limiting factor to yield, soil test levels will correlate closely to yield. There will be low fertility in the low yielding area of the field. When fertility, or the soil nutrient in question, is not the limiting factor, soil test levels will have an inverse correlation to yield, it will result in higher soil test levels in the areas of low yield.

Finally, we need to look at the behavior of the nutrients themselves. While the values can vary, it is accepted on average that for every 18-22 pounds/acre of P₂0₅ applied to the soil above crop removal, phosphorus soil test (Bray or M3) should increase by 1 ppm. Research is beginning to show that it takes that amount, or more, P₂0₅ removal to lower the soil test 1 ppm. A very good yielding crop may reduce phosphorus soil test levels 1-3 ppm/year or less.  Conversely it requires an application of 6 to 10 pounds/ac of K₂0 (depending on CEC of the soil) to raise the soil test 1 ppm (ammonium acetate or M3). Recent research indicates that though crop removal, soil test potassium levels can reduce soil test levels by 1 ppm with less than 6 to 10 pounds of K₂0 removal per acre. A good yielding crop can reduce soil test potassium levels by as much as 20-30 ppm/year.

Knowing these factors and how they interact helps begin to prioritize ways to reduce fertilizer application rates and the associated risk from doing so. Some suggestions may include:

• Reduce/stop fertilizer application on soil testing above max and possibly those above optimum.
• For soils testing below the target, consider reducing or removing any fertilizer rates above crop removal.
• Phosphorus rates can be reduced or eliminated for a short period of time with little impact on phosphorus soil test levels. Once the levels do start to decline, it will take a significant application to build back up.
• Potassium levels can drop quickly in high yielding grain or forage fields, application rates below crop removal should be kept to a minimum. More frequent soil testing is advisable to monitor soil test potassium levels during aggressive potassium application rate reductions.
• When soil fertility is limiting yield, be sure to focus on applying at least crop removal on soils below the target level. Using a yield map to better define crop removal rates is advisable.
• When soil fertility is not a yield limiting factor, shift the fertilizer to the higher yielding areas of the field to maintain or increase yield in those areas.
• Consider applying a percentage of crop removal, maybe apply 70-80% of phosphorus above target level and full crop removal below the target.

Evaluating how a cut in fertilizer application rates may impact the situation will lead to wiser budget cutting. The worst thing you can do is simply reduce standard recommendations by a flat percentage across the board. This will usually place the greatest yield production risk on the highest yielding areas. Your ALGL regional agronomist can help evaluate the various options based on your situation.