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Spring Tissue Sampling for Wheat Nitrogen Management

Spring tissue sampling of winter wheat can be a very useful management tool. The timing of wheat sampling does not correspond to a specific growth stage though. The important factor when determining the appropriate time to sample wheat is that the wheat has broken dormancy and is actively growing again. Generally, wheat will be at a growth stage of Feekes 3 or 4 when this occurs. The appropriate method for collecting wheat samples at this stage is to collect 25 or more whole plants from ½ inch above the soil surface. One of the benefits of early season wheat sampling is to fine tune a “green-up” nitrogen application based on the nitrogen content of the plant at Feekes 5 (please visit the Purdue Extension News Release for more information). 

Image: Feekes 5 wheat. Source: Kansas State University

Once the plants reach Feekes 6 and beyond, indicated by stem elongation and jointing, only the most recent fully developed leaf should be sampled. The most recent fully developed leaf is the highest leaf on the plant with a fully developed collar. Once the plant begins heading (Feekes 10 and beyond), the flag leaf should be sampled. Generally, 40 to 50 leaves should be sampled at these growth stages.

Accurate plant tissue testing begins with proper sample collection and handling. Make sure to collect the proper plant part for the current growth stage of the crop and collect the proper number to make the sample. This information can be found on the plant analysis page at algreatlakes.com. Always avoid soil contamination in your plant samples. Package samples in paper bags. If shipping is delayed, store samples in a cool location, but do not freeze. Never include roots with a plant sample. If you have any questions on proper plant tissue sampling, please contact the lab for assistance.

Fertilizing Fruit Trees

Fruit trees are a perennial, woody addition to any landscape, homestead or commercial operation.  Selection of varietals depends greatly on the intended use for the tree(s).  Ranging from landscape designs of flowering hedge rows to the intense production in commercial orchards, fruit trees have always been a part of America’s history.  Even though the term fruit tree is a very broad category, fertilizing them does not have to be. 

The first step to utilizing fruit trees is to select varietals that are suitable for that specific environment.  This is often referred to as climate zones, but this goes much further than a number on a map.  The environment also includes soil types and fertility, location, and drainage.  After a suitable location has been established, a representative soil sample(s) must be analyzed.  This is the point in a tree’s life that the soil environment can be both economically and efficiently amended for the best start.      

Soil pH is the priority when considering any soil amendment.  The pH directly impacts the availability of nutrients to plants.  Certain plants thrive in different soil acidities.  Blueberries, for example, do well in acidic soils.  A pH of 4.0-5.5 makes nutrients like iron more accessible.  Without the acidity of the soil nutrients are left unavailable to the plant.  Fruit trees grow and thrive in a soil pH of 6.0-7.0.  One careful note when analyzing soil acidity is that some nutrients levels become toxic at different pH levels.

Often, a grower will “amend” the soil in the newly dug rootzone.  The hole is generally dug wide and deep enough that the roots do not touch the edges when held in place.  Some will recommend mixing sand, compost, peat, coir, or different soil in the new tree bed.  This is a quick fix for certain problems such as drainage, nutrient requirements, and/or water retention but in some cases not the best option for long-term health.  This can lead to trees needing to be staked for proper growth direction from the root bed being too loose or soil surface being too low.  Some additions can lower the pH too much, and breakdown over time.  Creating a micro-climate for the root bed can lead to roots wrapping around the edges or not penetrating the outside walls into native soils.  The best option is to choose the right place to plant and add the native soil back to the hole.

If a soil test shows deficiencies of certain nutrients, it is important to know how much and of what specific fertilizer to address the issue(s).  There are fertilizers that are immediately available for plant uptake and others, like elemental sulfur, that are not. Some deficiencies could be from inconsistent watering/weather.  After two years from planting young fruit trees, regular watering should be less and less depending on climate.  This allows the roots to develop and not become too shallow and grow vertically rather than horizontally.  This is especially important in high wind environments where a deep root system provides stability. 

Early spring is the best time to fertilize fruit trees.  This allows the application to leach down into the rootzone from the ample, seasonal moisture.  Depending on the fertilizer used, it will give it time to convert to available forms.  Nutrients need to be in an inorganic formulation for uptake.  If a composted manure is applied to each tree, or blanket spread on the landscape, it will need time to mineralize.  The same process allows soil organic matter to release nutrients such as nitrogen and sulfur through mineralization.

Applications made in late spring, summer and/or fall may cause rapid growth too late in the season.  These later fertilizer applications can inhibit fruiting while producing vegetative growth and possible winter injury.  All living plants need nutrients, but production crops where the fruit is harvested requires knowing what is already available and what needs to be supplemented for that crop.

Impacts of the Dry 2024 Fall

During the dry soil sampling in the fall of 2024 there were quite a few questions about how the drought conditions in much of the ALGL trad area were impacting soil test data. At the time it was very hard to predict the impact on soil sample results. The resulting 2024 data has a much clearer picture. While the data presented in this article is for the entire ALGL trade area, like in 2012, the entire ALGL trade area was impacted by drought in 2024.

During extended periods of dry weather / drought, 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 of 0.1 to 0.6. Given that the drought set in for most of the ALGL service area later in the year after crop establishment the impact should have been reduced. 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 below the sampling depth. A simple reference is that when tiles are flowing water, water is infiltrating down through the soil profile and taking soluble salts with it.  

Looking at the soil pH data for 2024, the soil pH on average was not notably different than past years.

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 support optimum plant growth, less potassium may have been taken up by the crop. Looking to the 2024 potassium data, it resulted in above average soil test results and comparable to 2023. While isolated regions/area may have been impacted more, on average the dry soil conditions do not appear to have had a significant impact on soil test K results.

What is interesting about the 2024 potassium data is that there appears to be an upward trend in soil test potassium developing. Over the past 5 years the soil test K levels have increased on average with a corresponding decrease in the percentage of low testing soils. While it is still too early to make that statement with this data set, the trend may be developing.

Boron Management Basics

Soils in the Great Lakes Region are naturally low in boron. Over 60% of the samples analyzed at ALGL are rated as either low or very low, which is less than 0.6 ppm. Most crops respond best at a soil test level around 1.0ppm. While boron may only make up a small percentage of crop biomass, it can have a big impact on yields when applied correctly.

Boron is critical in building cell walls. So, it is important in all growth stages, but the greatest demand for boron is early in the reproductive stages when corn is forming pollen tubes and soybeans are flowering. Foliar boron applications need to be targeted a couple of weeks ahead of entering reproduction. Early season applications may not last long enough to maximize the benefits, and late season applications are not likely to produce a response.

Managing boron availability can be challenging. Boron is taken up by plants as boric acid, H₃BO or H₂BO₃^-₃. Being an acid, boron availability is greatly reduced on alkaline soils. Also, being a negatively charged anion means that it is prone to leaching. Foliar products should be used on alkaline and/or well-drained soils.

Broadcasting dry boron fertilizer products can be effective but needs to be applied carefully. Common application rates for boron target from 0.5 to 2.5 pounds per acre and common products range from 10-15% actual boron. This means that a very small amount of product needs to be uniformly spread over a large area. Boron can very easily become toxic even with a small over-application. A simple overlap in a spread pattern has the potential to lead to toxic levels. Some crops can experience toxicity at 2-3 ppm in the soil while corn and soybeans can tolerate boron levels up to about 5 ppm. In the case of an over-application, liming the area can be an effective means to reduce the availability of the boron.

Since boron toxicity is a very real concern, it is advisable to utilize foliar and broadcast application methods. Boron should not be used in any banded applications such as in-furrow, 2x2, or sidedress. The concept of banding fertilizer is to saturate a small zone in the soil to ensure availability, but in the case of boron it could easily lead to toxicity.

Contact your regional ALGL agronomist if you have questions about boron management.

Lab Questions – Impact on Hydrogen and Calcium Base Saturations When Lime is Applied

A question came to the lab. The base saturation numbers look a little out of whack on the soil test. The averages are: Ca-55%, H-23%, K-4%, and Mg-18%. Avg pH is 5.5 but is fairly uniform. Will a lime app bring the Ca% up and the H% down?

Keep in mind that the base/cation saturation will add up to 100% and the base saturation values are calculated from the soil test results (ppm or lbs/ac) of these nutrients. In some cases the hydrogen saturation is not reported so the reported numbers do not add up to 100%, but the hydrogen saturation is part of the calculations even if it is not reported. Adding any one of these nutrients should lead to a higher soil test result. These higher results will lead to a larger contribution to the base/cation saturation calculation for the applied nutrient and thus a higher percentage. Since the base/cation saturation must add up to 100%, when the percentage of one nutrient increases, the others must go down.

The H% is calculated from the buffer pH (or soil pH if calculated from TEC), as the soil is limed, the soil and buffer pH increases, leading to a lower calculated hydrogen percent. The reduction of the H%, leads to increases in the other cations. Addition of magnesium or calcium in the liming materials will also increase the soil test of these nutrients and effectively increase the relative percentages of both.

The Right Source of Potassium

Potassium, or K, is unique in a way that soils have a relatively large amount in the Midwest region.  Some soils can range from 15,000-20,000 ppm total K.  Even though there are large amounts of this macronutrient, it must be in an exchangeable form.  It is estimated to be only 1-5% is available and most soil contains approximately 1-3 ppm in the soil solution. 

Why is potassium so important?  Afterall, when reviewing commercial fertilizers, it is listed as the third number in the grade or analysis.  The functions of K in the plant are numerous.  It plays a key role in cell growth, photosynthesis, stomata function, enzyme activation, nutrient absorption and water retention just to name a few.  Using corn as an example, K deficient plants can experience marginal leaf necrosis, reduced plant height, poor reproduction and stalk lodging. 

There are multiple variables to consider when evaluating soil K levels.  Weather, residue, soil type and sampling habits can all play a large role in test levels.  Weather will affect the uptake of accessible soil potassium simply by not having enough moisture for uptake.  It is important to understand just because the crop is showing signs and experiencing symptoms of K deficiency, that environment dictates uptake of this macronutrient. 

When choosing the right source of potassium, or potash, do not over think what type of K is correct.  The K is nutritionally the same in all fertilizers.  However, many commercial fertilizers are not only K.  Some crops are sensitive to individual nutrient salts.  There are many soils with insufficient amounts of individual nutrients, and this is why it is important to select the correct type of fertilizer for individual cropping systems, soils and maintenance programs.

Here are some examples of potassium fertilizers and their composition.  Potassium chloride (KCI; 0-0-60) This is the most common for bulk blending and row crop agriculture.  This would not be a good choice for crops such as almonds since they are sensitive to Cl^-.  Potassium nitrate (KNO₃; 13-0-44) is an additional source of nitrogen and a good choice for chloride sensitive crops.  Potassium magnesium sulfate (K₂SO₄•2MgSO₄; 0-0-22) used to supplement magnesium and sulfur with K.  Potassium sulfate (K₂SO₄; 0-0-50-18) has a low salt index and includes sulfur.  Potassium thiosulfate (K₂O₃S₂; 0-0-25-17) is a liquid fertilizer and can be used in sidedress applications in dry conditions.  Potassium hydroxide (KOH; 0-0-75 has a high pH.  Often used as a liquid fertilizer that is absent of chloride and best used in acidic soils.   

Sample timing is critical when accessing K levels.  It is advised to pull samples after the same crop each time.  Soybeans, for example, will release potassium back into the soil much faster than corn.  As soon as the cell ruptures K is released and available.  It does not take a microbial process for availability.  This is why soil test levels vary greatly depending on sampling time and previous crop. 

Extreme, dry conditions can also impact soil test K levels as they become tightly bound to clay particles.  When making management decisions for potassium, always sample at the same time of year, after the same crop type, at the same depth/location and be mindful of current weather/environmental conditions when analyzing data.

Source: 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

Cutting Phosphorus Fertilizer Applications Without a Soil Test?

The current farm economy has driven a wide range of crop budget conversations. How to produce more with less is the key to the economics for 2025. But the key to that statement is twofold, we need to focus on maintaining and increasing yield while cutting costs. All crop inputs are in the cross hairs, but $800 per ton phosphorus products seem to have a bullseye painted on them.

Phosphorus is key in maintaining yield, so cuts to phosphorus inputs need to be made wisely. The idea of reducing phosphorus rates without a soil test is a recipe for problems, however there are producers looking to do just that. We have all heard of examples of producers getting good yields on soils testing low in phosphorus, so why fertilize? Why soil test?  The answer to this question is in data.

Often in publications, soil fertility data like this is summarized with the red line that leads the reader to think that as soil test phosphorus increases, yield increases. This can be misleading. When reviewing more detailed data, there are soils testing low in phosphorus (left side of the scatter plot) that are yielding near 100% of relative yield, and some at 60%. As soil test phosphorus levels increase (moving to the right), the top end yields do not change much (green line), but the low-end yields (yellow line) increase significantly.

Applications of phosphorus on low testing soils may not always increase yield but can mitigate the risk of low yields. This data also suggests that there is no value in building/maintaining a soil test above 40-50 ppm M3- ICP and soils testing less than 20-30 ppm M3- ICP are still potential candidates for phosphate applications.

A soil test can identify those fields that can forgo an application of phosphorus, and those fields that should have phosphorus applied to maintain yield potential, especially if the spring of 2025 soil conditions challenge early season root development. If you have any questions about phosphorus management, be sure to contact your ALGL agronomist.

Great Lakes Yield Enhancement Network

For growers and crop advisors in the Great Lakes Region looking to improve their wheat production, don’t miss the opportunity to participate in the Great Lakes Yield Enhancement Network (YEN). This program was developed not only to help growers increase yield, but also to improve wheat quality and profitability through collaboration among growers, crop advisors, and university researchers. Now entering its fifth year, this program has grown from about 50 farms to well over 200 and they would like to continue to grow. Many of the current farms enrolled in the YEN are in Michigan, but other states are welcome to participate.

There is a cost associated with participation in this program, but it includes multiple soil, plant tissue, and grain tests throughout the growing season. Each participant is given a detailed report about their wheat production and how many of their own metrics compared to the other participants at the end of the year. What makes this program unique is that it is not purely a yield competition. Growers are encouraged to openly share their practices and observations with other participants.

If you are interested in learning more, please visit greatlakesyen.com. The deadline for registration is nearly here to register for the 2025 season, but will reopen for 2026.

The Right Place for Potassium

For the past decade, agriculture personnel have been noticing the decline of soil potassium levels.  It is no surprise that as the yield potential for crops increases, so does the demand for more nutrients.  In many circumstances, these required removal rates are simply not achieved with current recommendations.  There may come a point where the correct crop removal rate is not affordable, creates too high salt concentration, soils are unable to support such rates, and/or equipment cannot apply these rates efficiently.  Choosing the right place to apply potassium can lend aid is such times. 

Most potassium (K), or potash fertilizers are spread on top of the surface of the soil.  They are generally blended in with products such as DAP or MAP for a fall or early spring application.  Most potassium fertilizers are soluble but do not move in the soil like other applied fertilizers.  This is because K is a cation and much of the soil, primarily clay and organic matter, is negatively charged.  The process of binding soil particles and K is known as adsorption.  This is why it takes the correct placement of the fertilizer.  It would be counterproductive to place a K application where the roots of the desired crop will not be. 

Crop types and rotations should affect applications.  Some root systems can reach deep into the soil profile, while others are shallow and grow more horizontally.  Already stated above, K is not very mobile in the soil profile.  There are many different cropping techniques and systems that all require potassium for a successful crop.  Let’s use corn as an example.  A majority of the K is surface applied as a dry product.  Once the fertilizer has been spread, or blown on, it must be incorporated. 

How fast the applied product gets to the root zone of the intended crop relies heavily on the product used, soil type, precipitation and current nutrient values.  When the product is mechanically incorporated, it is fairly simple to achieve even distribution.  Tillage makes it easier to apply higher rates without experiencing stratification of K fertilizer.  Although it can happen at shallow working depths.  Fertilizer stratification is when nutrients are unevenly distributed.   Often a surface application in no-till conditions will concentrate the nutrients on the surface, rather than in the root zone. 

In a no-till system, surface applied nutrients must be incorporated with water.  This makes it especially difficult when trying to raise pH and applying K fertilizer.  Both are being concentrated near the surface, binding to negative soil particles.  Soils with a lower CEC, cation exchange capacity, will be able to achieve nutrient accommodations lower in the soil profile much sooner than high CEC soils.  Once the exchange sites are full, nutrients like potassium will infiltrate deeper.  If large amounts of K applications are made near newly planted seeds, salt damage can occur. 

A management strategy to combat nutrient stratification, potential erosion issues with conventional tillage and dispersing inadequate rates via broadcast is strip-tillage.  This is essentially banding the product in, or just below, the root zone.  Some describe it as the best of both worlds, but it too has its challenges.  It can require expensive equipment.  Not only the strip-till bar, but the distribution system, meters, rate controllers, plumbing and enough tractor to have it effectively work.  It can also be slow depending on rate, product, soil type and terrain. 

With any potassium application, it is important to implement the 4Rs for the best environmental practices and return on investment.

2024 In Review - A Lab Perspective

Editorial by Agronomist Jamie Bultemeier

It seems as if the past few years have found new and intriguing ways to challenge agriculture. 2024 was up to the task and on par with that trend. This year has brought a wet spring for some, a dry summer and fall for most, and a shortened growing season for all. These challenges have also impacted the lab.

The spring soil sample season began early this year in January. There was a very brief pause between 2023 fall soil sampling finishing up in late December and spring 2024 soil sampling starting in early January. January 2024 produced the 2^nd largest January of soil samples in lab history. January was followed by record February and March sample volumes. The spring rains were just enough to delay planting, but not soil sampling. Strong spring soil sample volumes continued through April and May when in-season sampling began. In season sampling carried the strong soil sample volumes through the month of June.

About the time the spring soil sample season was slowing, plant tissues began. A week or two earlier than normal. There was no break between the two seasons. The rapid fast paced operation of the lab continued without a break at record plant tissue test sample volumes in July.

While soil samples did set more monthly records in the summer months, the lab staff did get a very short, but needed break, in sample volumes in August. However, the break was short lived. The hot dry weather accelerated crop development from north to south in our trade area and the fall soil samples arrived early and without delay. Usually fall soil sample volume ramps up over a 3-4 week period, not in 2024… The lab went from a few thousand to full capacity in about a week. This fall there was no widespread or regional rains to delay or slow soil sampling. The samples came fast, in large numbers, and constantly for weeks. Breaking more monthly sample volume records in September and November necessitating the need for the staff to work several weekends in the pursuit of maintaining a reasonable sample turn time for our customers.

All of the 2024 weather challenges compounded for the lab, yet 2024 was a great year. For the first time since 2020 we had a complete staff, and great fall seasonal staff that stuck with the lab for the entire season along with many that returned from last year. We had amazing support from our customers with unparalleled kindness that grew as the year progressed into fall soil sample season. The positive notes written on shipping box flaps, submission forms, and extra notes shipped with the samples had a bigger impact than you can imagine. We had fun through social media noting the staff’s fondness for candy, and the candy that arrived in sample boxes made the long day easier and gave them more purpose in their work.

Reflecting back on 2024, I sit in awe of what we accomplished in partnership with our customers. While the term partnership is often overused, it is the only term I have to describe the working relationship between the lab and our customers. I can recount numerous examples of the lab and customers working together in full cooperation to meet the needs of our collective customers, breaking records all along the way.

As the year draws to a close, I am reinvigorated with the potential in this industry. The level of professionalism in our customers is outstanding and it only reinforces that we are fortunate to have a great customer base that we can grow alongside.