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Which is Better, Bray-1 or Mehlich-3?

(…another agronomy rant from another agronomist at ALGL, David Henry. Once again, this is not directed at any particular entity or person, just a response to an often-misunderstood topic in the industry.)

Asking which phosphorus extraction (Bray-1 or Mehlich-3) is “better” is like asking if inches or centimeters are better at measuring length. You are measuring the same thing, just using a different scale.

In fact, most people who work routinely work with soil test data, likely have never seen an actual Bray-1 value. This is because the Bray-1 and M3 phosphorus extractions are very well correlated to each other. This means that given either value, you can calculate what the other is with a high degree of certainty. As a result of this, most commercial soil labs adopted the M3 extraction as their routine extraction method 2 or 3 decades ago but can still report a Bray-1 value.

Why is this? You might ask. Well, the M3 extraction is also very good at extracting other nutrients. Like nearly all of them that we are interested in when growing plants. From a laboratory efficiency standpoint, M3 is far superior to Bray-1. For the end user, it really does not matter. As long as you know which value you are working with and are using the appropriate interpretations and equations, one extraction will not give you better crop production results over the other.

Manure’s Impact on Soil pH

Most manure sources can be an incredible addition to row crop farming operations. If it is handled, and applied, in an environmentally conscious manner it will provide long lasting results for multiple growing seasons. When utilizing manure is an option, there are several factors that should be taken into consideration. The species from where it came from, feed, storage, bedding type, and application methods.

The type of manure, from which species it comes from, will have drastically different manure analysis results. To use one example, below is a table from A&L Great Lakes Laboratories depicting the differences between species with both solid and liquid forms of manure and their inorganic to organic comparisons.

Ammonium content, an inorganic form of nitrogen, will acidify the soil as it undergoes nitrification converting to nitrate. On the other hand, there are several manure sources that will increase the soil pH. This is credited to the amount of carbonates and bicarbonates are in the manure.

The type of feed and bedding can have a large impact on the alkalinity of the manure. Some manure from poultry sources, that include calcium carbonate in the feed and eggshells, can increase soil pH for the next several years after application. Bedding can also be a high source of liming material. The sand, in sand bedded dairies, can be sourced from high alkaline parent materials.

It is important to analyze the manure and know the source and type of manure before application. The ammonium content and calcium carbonate equivalent (CCE) of the manure can be determined by lab analysis. Some soil types, topography and soil nutrient levels may impair the use of manure as a fertilizer source.

Late Season Nutrient Diagnostics

It is common for nutrient issues that went unnoticed during the growing season to become apparent as harvest approaches. With the growing season coming to an end, what can be done to diagnose potential nutrient issues as corn and soybean harvest approach? The options become increasingly limited as the plant gets closer to harvest maturity.

While tissue tests are effective for identifying nutrient deficiencies during the growing season, the remobilization of nutrients within the plant, combined with the loss of dry matter due to tissue senescence, can artificially alter nutrient concentrations in the plant sample. This can occur after R3/R4 in soybeans or R3 in corn. Beyond these points, plant senescence will lead to nutrients leaving the plant and alterations in biological processes that will not be reflected in reference data. Dead and/or yellowing tissue will not produce valid tissue test results. Corn that maintains a healthy ear leaf is more likely to produce meaningful tissue test results.

Near these growth stages, “good” vs. “bad,” or perhaps more accurately “bad” vs. “worse,” tissue test comparisons can yield insight into potential deficiencies. These results can also be highly subjective and should be carefully considered. A high tissue test level at this time is not necessarily a good thing. Rather, it is often the result of an associated deficiency in which that nutrient was not efficiently used and remains in excess.

Soil tests can often be more useful at this point in the growing season. Just before harvest often reflects the lowest point of nutrient availability in the soil. Don’t forget to test for micronutrients as well. Sample the negatively impacted area directly, as it may be small enough that it is not reflected in routine soil testing. Again, comparing a “good” vs. “bad” soil test is a good practice in this situation. This may provide additional information to further define the issue, especially when more than one nutrient interaction is involved.

In corn, a stalk nitrate test can provide additional insight into the conditions leading up to the visual symptoms. Late-season issues are often identified by changes in yield parameters, such as the number or size of ears, and nitrogen often plays a role. If the “bad” corn has an excessive stalk nitrate level, the issue likely arose late in the season and limited the plant’s ability to achieve a higher yield goal. If the “bad” corn has a very low stalk nitrate level, either the nitrogen program was limiting, nitrate loss was excessive, or the root system was not developed enough to access nitrogen. Additional data can be evaluated, or additional observations can be made, to confirm or rule out these possibilities.

Digging roots and evaluating stalks should be done before harvest. Limited root development can also be associated with low phosphorus levels. Evidence of a limited root system can provide insight into late-season tissue samples or interactions with limited soil fertility.

Notice that may, may be, should, and could are used frequently in this article. Late-season diagnostic laboratory analysis can be used to help define the cause of an issue; however, a critical evaluation of the data is required. Seasonal environmental conditions and crop physiology can significantly impact laboratory results, and those effects are not predictable.

Fertility Management for Landscape Trees

We have recently seen an increase in homeowners and tree care services interested in testing soil and leaf tissue for better nutrient management for ornamental landscape trees. While these services can certainly improve performance and appearance, fertility management for trees and other deep-rooted plants can be challenging. Please keep in mind that these comments are not meant to replace the advice of a reputable arborist. When establishing new plantings, it is best to select species that are well suited to the climate and soil types in your area.

The proper method for collecting soil samples for trees is not well defined. Some may argue that the sample should be collected to the rooting depth of the tree. Since most trees can root 10 feet deep or more, this is not very practical. A more appropriate method would be to collect the samples to a depth that can be impacted by a fertilizer application. This would be a 6-12-inch-deep sample in most situations. Deeper samples may be helpful to better understand the pH further down in the root zone, but incorporating fertilizer that deep may not be possible. Keep in mind that a tree’s root system has access to much more soil than a typical soil sample represents. So, ideal fertility levels are relatively low. Trees in a well-maintained landscape or lawn setting often do not need additional fertilizer than what is already being supplied around them.

Leaf tissue testing can be an excellent tool to help determine what nutrients may be lacking in a tree. Since soil testing has limitations, the leaf tissue can help fill in the holes. Deciduous landscape trees in the Midwest often struggle with micronutrient availability due to the alkaline subsoils that sit on top of limestone bedrock. Iron and manganese deficiencies are very common. The symptoms of micronutrient deficiency are generally chlorosis of the newer leaves. A challenge in diagnosing a nutrient deficiency visually is that damage from pests and pathogens can look very similar. One way to potentially differentiate a nutrient deficiency from disease is to look for a pattern. A nutrient deficiency is more likely to follow a distinct pattern from bottom to top or top to bottom and on the individual leaves themselves from the outer margins working in or the middle working out. Disease damage tends to be more random.

Unfortunately, one situation where soil and leaf testing does not help much is when an old, well-established tree begins to show decline. Once this has begun, fertilizer is not likely to correct the issue because it is often the result of changes in the surrounding environment.

Fall Sampling Season Checklist

Fall soil sampling season is soon approaching. To ensure as few disruptions as possible once the sampling begins, here are a few points to address now.

1. Contact the lab or your ALGL regional agronomist to update your account if there have been changes in staff, email contacts, or phone numbers. Be sure to consider all those employees involved in the process, samplers, accounting, sales and consulting.
2. Update your Client Portal Access. Those customers who are designated as Account Administrators can add new users to their account and select which portions of the Portal can be accessed. This can be done without contacting the lab.
3. Please let us know if there have been any changes to your normal sampling routine such as hiring a new sampling service or using a new shipping provider. This will help the lab staff to better communicate potential issues to the correct contacts.
4. If you have made a change in software, contact your ALGL regional agronomist so they can modify your account settings to ensure that the data flow is correctly configured. It is also a good idea to do a test with a small sample number to ensure the data flows correctly and any needed changes in procedure are identified before the season starts.
5. Order soil bags and shipping boxes ahead of time. Please coordinate with your ALGL agronomist to schedule delivery or pickup of large orders.
6. Check your UPS shipping labels. Do you need more or have they expired? The expiration date is on the lower portion of your UPS labels. After this date the tracking of the package can become unreliable. If you need new labels contact the lab or your ALGL regional agronomist and they can get new labels on the way. Remember that you can create shipping labels on the Client Portal. This is not necessarily a replacement for ordering preprinted labels but can save a lot of time in a pinch.
7. At the beginning of each year a summary of the previous year’s samples is posted to your eDocs account. That report shows what fields by grower/farm/field that were sampled each year. For example, if you sample every two years, you can look back to the 2024 sampling report to ensure no resampling is missed.
8. If you are sampling fields that you have previously done, take the time now to pre label the soil bags and pre generate labs submission forms.

Your ALGL agronomist is available to discuss your soil sampling protocols and help find ways to streamline your fall soil sampling.

The Rest of the Story…

Editorial by ALGL Agronomist Jamie Bultemeier

Time has faded the memories of Paul Harvey’s radio program, but there was tremendous wisdom within it. The key to his storytelling style was holding back one key fact or element of the story until the end of the program. Paul Harvey revealed the missing link at the very end of the program, making the story or message complete. We don’t always get that missing link in agriculture, and often the audience does not want to find it. They prefer the story as it is.

Each summer, I am fortunate enough to attend and participate in a variety of events as they pertain to soil and crop fertility. Over the past few years, I have found more “data” and fewer statistics and research fundamentals. This is not an article on statistics or research design. The greater concern is the misleading messages supported by this “data.”

I get it. Stats are boring, and taking time to explain the research study behind the data is a buzzkill to a fast-paced presentation. But sometimes we need to slow the pace and fully explain the results so that the “data” is not misleading.

One such example from this summer was a farmer presenting at a field day and sharing the impacts of soil conservation on their farm. One of their key messages was that through no-till, cover crops, and improved management, they had improved soil structure and increased organic matter. The farmer had a data table showing the farm’s average soil organic matter over more than a decade, and it was increasing. This same data table also displayed the averages of several other soil test parameters, and comments were made to illustrate the shifting of soil test nitrogen and phosphorus from inorganic forms to organic forms.

The producer then went on to their next key point, noting that this new farming style afforded them the ability to reduce nitrogen rates by 60% and eliminate phosphorus fertilizer applications. The fertilizer application rates had been decreased in small increments over the past 10–15 years while maintaining yield. The crowd of fellow farmers was buzzing with excitement about the idea of massive reductions in fertilizer application rates. This would be a significant reduction in production costs at a time of low commodity prices. The presenter attributed these fertilizer reductions to improvements in soil health.

The unasked question was, “How is this possible?”

Their soil test phosphorus levels were several times higher than the levels requiring phosphorus fertilizer, and 6–8% Illinois soil did not require 250 units of N to produce an average corn yield to begin with. The farm had historically been over-fertilized, and proper soil testing had now resulted in appropriate fertilizer application rates.

Now you know the rest of the story.

But this story doesn’t end here…

The fertilizer reductions achieved had nothing to do with increased soil health. The nutrient reductions could have been achieved decades ago with sound nutrient management. Because of elevated soil fertility, there was little to no risk in making these cuts.

Most of the farmers in the room did not have the same high phosphorus levels and/or high organic matter levels, nor a critical understanding of soil fertility, yet they eagerly wanted to believe that increased soil health would allow them to make these same nutrient application reductions while maintaining, or even increasing yield.

It may. But what if it doesn’t?

Lime Incorporation Depth and Application Rates

When discussing soil acidity, the conversation starts with the soil pH. pH is the measurement of hydrogen (H⁺) in the soil. It will determine whether the acidity in the soil needs to be adjusted. Next is the buffer pH. This is not recognized by all recommendation sources, but it is a very useful tool when preventing incorrect application rates. Next is the source of lime, depending on the soil analysis, to use calcitic or dolomitic limestone. The calcium carbonate equivalent (CCE) will determine when the product will reach its full potential by neutralizing the given soil acidity and plays a large role in application timing. The last piece of the liming puzzle, although there are many logistical steps not mentioned, is incorporation.

Many recommendation sources include incorporation rates for different tillage, or no-till, scenarios. Why does this matter? When correcting soil pH, it is not just the pH and buffer pH that determines the application rate but there is a volume of soil that makes a large portion of the equation. To interpret a soil analysis, the soil pH will determine is the soil needs lime. The lower the pH number, the more hydrogen or more acidic the soil is. A 5.5 pH is ten times more acidic than a 6.5. The buffer pH will determine how much to apply. The buffer pH is measuring the reserve acidity. A strong buffered soil will have a lower buffer pH analysis. A weakly buffered soil will have a higher number.

A physical lime prill, granule or particle will only neutralize a small amount of its surroundings. If the product is applied to the surface of soil, such as when practicing no-till, it will take an extended period of time for the product to reach the root zone of the intended crop. According to The Ohio State University, lime will only move into the soil profile at a rate of approximately 1” per year. This will be highly dependent on soil type and CEC. Before converting to a no-till system, it is important to start with a manageable soil pH. Or, if the soil is erodible, utilize options such as subsurface applications.

When surface applying lime, most sources will recommend a half, or reduced, rate. This is to prevent the surface soil from becoming overly alkaline. When a seed is planted it starts at the surface level, then it taps into deeper resources as it matures. This can create nutrient availability issues early in the plant’s life, but can outgrow them as a deeper, more robust root system develops. Even though a 6-8” soil core may result in a 6.5 pH, the top few inches could be 8 and the bottom part of the core a 5 pH in a no-till scenario. Tillage, although not applicable everywhere, creates uniformity to the tillage depth. This depends on tillage type, implement characteristics, disturbance level and soil type.

Always follow calibrated recommendation resources based on lab analysis. Lime applications are not an immediate fix and can take even longer depending on application practices, soil type and lime sources.

Johnson, J. W., & Myers, D. (2015). Most asked agronomic questions: Bulletin 760, Chapter 1—Liming and pH. The Ohio State University Extension.

Agronomy Rant - Reading Lab Reports

Editorial Note – This editorial is an overgeneralization of common terms that are often misused in soil fertility. It is not directed at any one entity. It is intended to be informative and mildly entertaining. Please keep in mind that the agronomists at ALGL spend a considerable amount of time with soil and are often isolated from human interaction with the outside world. Therefore, the phrase "mildly entertaining" is highly subjective.

We have all heard the phrase "reading a soil test report" or "reading a tissue test report." Although the apparent task may be readily inferred through superficial observation, such a characterization is wholly inconsistent with the actual procedural and operational semantics of the process. Or, to put it more simply, that may appear to be what is being done with laboratory results, but it is not how the process actually works.

We read text and interpret data. Read means to look at written words and understand their basic meaning. Interpret means to explain or determine what something means, often going beyond the literal words or data.

Like all agricultural laboratory reports, soil and tissue test reports contain data. The data itself has little, if any, meaning without additional interpretive information derived from university- or industry-based research. Once that interpretive information is applied, informed and prescriptive decisions can be made based on the data.

A good example of data interpretation can be found in our blog post, Lab Tests and Fuel Gauges. We can observe data values, but without interpretation we cannot make prescriptive decisions or take meaningful action to influence future outcomes. Without interpretive information, we can only track changes in the data and that is how researchers build the interpretative data.

One does not simply “read a soil test report”, one “interprets a soil test report!”

This concludes the Rant

The Push for Higher Soil Calcium Levels

Calcium, like most recognized soil nutrients, plays a large role in overall plant success. It is the foundation of cell walls, promotes root growth, acts as the plant’s defense, and helps manage stress. This macronutrient is readily available in most Midwest soils, however, there has been a movement to increase the soil calcium levels regardless of soil test levels. Have you ever experienced calcium deficiency?

Having adequate calcium levels is necessary for the most productive crop, but what happens when soil levels are excessive? The goal of increasing soil calcium levels is to remove magnesium from the soil colloid in hopes to maximize flocculation. Flocculation is when clay particles clump together forming aggregates, or larger clusters of soil particles. Calcium binds to the soil colloid stronger than magnesium and can form larger aggregates such as blocky formations. This is crucial for water drainage, root penetration and pore space but creating excessive soil calcium nutrient levels is unnecessary.

What is the correct calcium to magnesium ratios and levels? When discussing these two ranges of sufficiency levels, it is entirely dependent on soil type, parent material and region. The parent material, or the original base layer of the soil, is constantly being weathered and breaking down. This releases nutrients such as magnesium depending on the type of parent material. When examining soil test results, a 1:1 ratio of calcium to magnesium involves alternate management decisions. This is often switching from dolomitic limestone, which consists of about 11% magnesium and 21% calcium, to a high calcium lime like calcitic limestone, which contains about 40% calcium and .2% magnesium.

In The Great Lakes Region, higher magnesium to calcium ratios is not unheard of but exist in certain concentrated areas. These areas usually have a lighter CEC, or cation exchange capacity. This creates another challenge for applications and rates. If the CEC is low, there are fewer exchange sites on the soil colloid. Once a high calcium lime is spread, it can dramatically reduce the number of other cations on the colloid. Other cations, such as magnesium and potassium, are then leached away with calcium remaining on the exchange site. Magnesium is the center of chlorophyll. The main energy source for all living plants. Negative impacts of high application rates can reduce yields at a much greater rate than trying to achieve a better calcium to magnesium ratio.

Before making a management decision, there are some questions to answer with appropriate responses. Is the soil pH where it needs to be? Are calcium and magnesium in the sufficient range? What is the CEC? How many sampling events are providing this data, and are the levels consistent? It is recommended to not apply more than 2.5 tons of liming material in one application for most soil, and 2 tons for soils with lower CEC.

Tips for Summertime Lawn Care

The hot, dry, late summer months can be stressful on lawns. Lawns throughout the Midwest and Great Lakes regions are generally comprised of cool season grass varieties such as fescue, ryegrass, and bluegrass. While these varieties are adapted to surviving cold winters and thrive in cooler spring and fall conditions, they can struggle to maintain the desired appearance during the hottest times of the year. Here are a few tips to keep your lawn looking its best.

Fertility – A properly fertilized lawn is better able to withstand the stress of hot, dry weather even though it may still turn brown. The difference is that a nutrient deficient lawn is more likely to die under heat stress, where a healthy lawn may go dormant and quickly rebound when conditions improve. However, once a lawn has gone brown, fertilizer applications will not fix the problem if the weather is still not fit.

Nitrogen – Most lawn care programs will recommend nitrogen targeting about 4 pounds of nitrogen per 1000 square feet split into 3 or more applications throughout the growing season. Fertilizer products formulated for lawn use are generally treated to slow the release of nitrogen and may contain some potassium and traces of other nutrients such as sulfur and iron. This is a great start since grass responds well to nitrogen, but they generally do not address all the fertility needs of a healthy lawn.

Phosphorus and Potassium – P and K both play several important roles in plants. The most important roles for promoting a healthy lawn are that P stimulates root growth and transports energy and K regulates water movement within the plant. Residential lawns are often deficient in P and K since the soil used to construct the lawn is usually subsoil left from the construction of the house. A routine soil test will indicate if P and/or K fertilization is needed. Lawns should have a Bray P1 around 25 to 40 ppm and K around 150-200 ppm. If P and K are needed, the recommended amounts should be applied in the spring and/or fall when temperatures are cooler and soil moisture tends to be higher as these are generally fertilizer products with a high salt index that have the potential to cause damage to growing plants if they are stressed. Once desirable levels of P and K are reached, if the clippings are not removed from the lawn, little or no additional P and K are needed to maintain the levels.

pH – Management of the pH is critical for assuring nutrient availability. A routine soil test will indicate if the pH needs adjusted. Lawns perform well in a pH range of 6.3 to 7.3. If the pH is lower (acidic) it can be easily corrected with lime. Alkaline (high pH) soils are common due to the subsoils that make up many yards. High pH is much harder to correct but can be done through repeat applications of elemental sulfur in the spring and fall, but it may take 2 or more years before a noticeable change happens.

Aeration – One of the challenges with hot, dry conditions is that the soil is generally hard and crusted and what little precipitation there is often comes in short, intense events that quickly runoff or evaporate before the moisture can soak into the root zone. Having a will aerated lawn will help to improve water infiltration and utilization.

Irrigation – Irrigation certainly has the potential to minimize the effects of the stressful summer heat, but it is important to make sure that the water being used is not causing any additional problems. Most well and municipal sources of water will have a high pH. Continuous use of alkaline water can cause nutrient tie-up in the soil. Avoid using softened water. Softened water, from conventional treatment systems, will contain sodium which at high levels can be toxic to plants and destroy soil structure. Irrigation systems are generally plumbed separately from the interior plumbing to avoid this, but if using an outdoor spigot to run a sprinkler, this water may be softened. If so, bypass the softener while irrigating.

The key thing to remember to keep your yard looking its best is that most lawn care services do not address the P, K, or pH needs of your lawn. They generally apply only nitrogen fertilizer and insecticide and herbicides when needed. A lawn can look very good with frequent nitrogen applications but can quickly fail when stressed. Managing the other aspects of the lawn are generally up to the homeowner.