News

“Good’ Vs. “Bad” Tissue Test Data in a Challenging Growing Season

Tissue samples are often submitted to the lab with the sample ID ‘s of “good” and “bad”, and sometime the tissue test data results are very similar. The dry weather this year has increased the appearance of these samples. Sometimes the “bad” sample will have higher nutrient concentrations than the “good” sample.

It is advisable in tough growing conditions to take both a “good” and “bad” sample. In some cases, the samples should be labeled “bad” and “really bad”.  Even the better appearing plants may be struggling and result in low tissue test values, just not as low as the poor appearing plants.

Tissue testing lab methods are a complete acid digestion of the plant materials. The concentration is the relative amount of a given nutrient within a defined volume of plant biomass. Changing either the total amount of nutrient in the plant or changing the overall volume of plant biomass will impact the results.

The impact of nutrient uptake and plant size on tissue test results when comparing two samples.

If nutrient availability in the soil is not limiting, there is no reason to expect the tissue test data between a “good” and “bad” sample to be significantly different. If a plant is limited by physical or environmental factors leading to reduced plant growth, the biomass volume of the impacted plant will be less.  Equally decreased nutrient uptake by the impacted plant will lead to a less total nutrient in the plant tissue tested. Often the decrease in plant biomass is correlated to the relative decrease in nutrient uptake. This leads to a very similar sample nutrient concentration. If the plant biomass is severely impacted while nutrient uptake continues, the impacted plant could result in elevated nutrient levels. Notes and pictures taken at the time of sampling can be very valuable in interpreting plant tissue data.

When a nutrient deficiency is occurring, it normally only impacts one or possibly two nutrients. When all or several of the nutrients are shifted, then external forces like lack of water limiting mass flow uptake of nutrient or soil compaction reducing root mass may be the cause. This is why taking a soil test close to the sampling location of the tissue test is very helpful. If the tissue test is low and the soil test is low, there is a lack of supply. If the tissue test is low and the soil test is good, then there is a lack of access.

Getting a tissue test report back from the lab showing that both the “good” sample and “bad” sample have adequate nutrient concentrations to support plant growth does not mean the tissue test did not tell you anything. It means the issue affecting the growth of the “bad” sample is most likely not directly related to specific nutrient deficiency. Contact your ALG agronomy representative for support using plant tissue data in diagnosis situations.

How is the Dry Summer Impacting Your Lab Results?

While much of the Great Lake’s region was fortunate to get some rain in the last couple of weeks, we still remain well below average for the growing season. These dry conditions are having an impact on the results of some soil and plant tissue tests.

One of the most noticeable trends is very low potassium levels in corn tissue samples. When testing the most recently mature leaves of corn in the V5 to V7 growth stages, the normal potassium level ranges from 2.0% to 2.5%. This summer most corn samples are below this range with a surprising number of samples showing severely low levels below 1.0% potassium.  While potassium soil test levels have been steadily declining for several years, that is not the likely cause of these low tissue tests. The plants simply cannot take up the potassium that is there. Plants take up potassium through two main mechanisms, mass flow and diffusion. Both require adequate soil moisture to occur. This means that adding more potassium to these fields is not likely to correct these deficiencies until we get some more rain.

Another common trend is high testing soil nitrate levels. This is the result of there being just enough moisture for the soil microbes to mineralize and nitrify the nitrogen from soil organic matter and manure, but not enough moisture for efficient plant uptake or to leach the nitrate through the soil profile. This has made it very difficult to decide how much additional nitrogen should be used in a sidedress application. Traditional PSNT interpretations will say that no additional nitrogen is needed when soil test levels are greater than about 25 ppm. In a season with adequate moisture, soil nitrate levels are often 20-40 ppm. This season nitrate levels have commonly been between 50-100 ppm. Some will take a conservative approach and not apply any more nitrogen with the expectation yields are likely to be reduced with the dry season. Some will still apply some additional nitrogen while there is an opportunity to make the application in hopes we will get more moisture as the season progresses. Either approach is justified. Unfortunately, we might not know if we made the right decision until the combine goes through the field this fall.

Routine soil tests so far this season do not seem to be impacted by the dry conditions. However, should the droughty conditions continue, this could potentially change as samples are collected following wheat harvest and into regular fall sampling season. The two most common measurements impacted by drought conditions are potassium and pH. The potassium levels will be lower due to collapsing of clay particles trapping potassium inside. The pH can possibly come back lower than it should be due to excess salts in the sample that interfere with pH electrode readings. Fortunately, it takes a severe drought to have extreme impacts on routine soil tests. We have not seen this level of drought since 2012, and hopefully won’t anytime soon.

Tips for Getting the Best Possible Results from Plant Tissue Analysis

Plant tissue testing continues to grow in popularity as growers and crop advisors work to fine-tune their fertility programs. With the ever-increasing costs of inputs, it is important to identify which ones are necessary and which ones work. Plant tissue analysis can help in several ways. It can potentially identify a nutrient deficiency prior to the development of visual symptoms. It can be used as a general monitoring of an overall fertility program. It can be used as a comparison between areas of a field that are obviously performing differently. Whatever the reason for collecting a plant tissue sample may be, it is critical to get a good quality sample to the laboratory. Here are some tips to help ensure that you receive reliable data back from the laboratory.

• Be sure to correctly identify the growth stage of the crop. There are numerous guides and diagrams available from university extension programs as well as commercial companies. Compile a small library for the crops that you routinely scout.
• Collect the proper plant part for the current growth stage. For the common row crops in our region, the proper plant part to sample changes throughout the growing season. Failure to submit the correct plant part will result in erroneous sufficiency ratings.
• Never send plants with the roots still attached. Early season plant samples often call for collecting the “whole plant”. This means the above ground portion. Plant should be cut off about ½ inch above the soil surface. Including the root material will result in contamination of the sample with soil primarily impacting the iron and aluminum levels in the results.
• Package your sample correctly. Always pack plant samples in paper bags. If you do not have the sample bags provided by the lab, brown paper lunch sized bags work as well. Do not use plastic bags for plant samples. Plastic bags seal in the moisture and speed up the decomposition of the plant material.
• When shipping multiple samples in a box make sure that the sample bags are secured so the samples do not dump out of the bag and do not over fill the shipping box. Stuffing too many plant samples into a box will also speed up the decomposition.
• Avoid shipping plant samples over the weekend, especially a holiday weekend. Packages shipped over the weekend are generally stored in trailers. During the heat of summer this could be detrimental to plant samples.
• Ideally plant samples are collected and shipped to the lab on the same day and only spend one or two days in transit. This is not always possible due to logistics and the weather. If necessary, let the plant material start to dry out. Spread the plant material out in a dry location and let it begin to airdry then repackage the sample and send it to the lab when it is convenient. All nutrient analysis is done on dried plant material. Starting the process will not impact your results.

If you have any questions or concerns about plant sample collection or shipping process, please do not hesitate to contact us. The customer service and agronomy staff will be more than happy to assist.

So Why Did the Label Position on the Soil Bag Change?

There have been quite a few questions about the label position on the new soil bags. Below is a picture of the new soil bag on the left and the previous soil bag on the right.

The area for those clients using pre-printed bag labels was moved to the top of the bag from the bottom while leaving the area for handwritten bag labeling in about the same place. There was good reason for the change.

When the bags are in the inbound process we call “layout”, the bags are lined up in submittal form order on tables. This process allows lab staff to verify that all samples listed on the submittal form are present and accounted for. Before the samples are placed into drying containers, the order of the samples is verified. The information at the bottom of the soil bag is very hard to see. Most inbound samples use pre-printed labels on them and are difficult to check when placed at the bottom of the bag. Below is the view of a staff member verifying sample order when the labels are at the bottom of the bag.

If you find the label position at the top of the bag problematic for your sample collection procedures, please place the label as high up on the bag as possible.

Potential Nitrogen Loss When Wheat Was Top-dressed With Urea or UAN

Questions have been coming into the lab about potential nitrogen loss from urea-based wheat top-dress applications made this spring. Many of these questions are being raised due to weather patterns around application timing.  Early spring applications were often followed by heavy rain fall, while late applications were followed by warm dry soils. While nitrogen loss is always difficult to predict, there are some basics taking place in these situations. To start, both dry urea and liquid UAN, which is 50% urea-based nitrogen, are subject to three nitrogen loss mechanisms, volatilization, denitrification, and leaching.

The naturally occurring urease enzyme in the soil converts urea into ammonium, the ammonium can be lost to the atmosphere as a gas during this process if the ammonium is not captured by the soil. Conditions that promote this are surface application on very dry or moist soil with delayed or light rainfall (less than 0.2”-0.3”, following application), heavy residue, and high humidity. These conditions impact dry materials greater than liquid, especially when the liquid is concentrated in bands. These low moisture situations can lead to the dry granule dissolving and not having enough moisture to move into the soil. Dry urea requires about 0.5” rain to incorporate into the soil where the urease released ammonium can be captured by the soil. Liquid UAN takes less rain to incorporate and even less when branded/streamed. Steady winds, delays between light moisture events, high soil pHs, and warm air temperatures above 70 degrees Fahrenheit will accelerate urea nitrogen loss to urease volatilization.

The next potential loss of nitrogen is from the rapid conversion of ammonium-nitrogen to nitrate-nitrogen that can be lost through leaching or denitrification. For urea-based nitrogen sources, the conversion of urea to ammonium is slowed by cold soil temperatures reducing the overall amount of ammonium nitrogen subject to conversion to nitrate that can be lost. For UAN half of the nitrogen is in ammonium or nitrate forms to start and can be subject to loss quicker than pure urea in dry forms. Short spells of warm weather can lead to rapid conversion of ammonium to nitrate. Warm saturated soils are needed for denitrification and leaching to occur.

Volatilization can be significantly reduced with the use of Agrotain (NBPT), which is commonly used on dry urea. Denitrification can be slowed greatly with the use of Instinct (nitropyrin), usually used with UAN to delay the conversion of ammonium to nitrate. Research has shown that ammonium thiosulfate is not as effective as these products but appears to have significant activity in reducing nitrogen loss by both mechanisms.

This Spring early season wheat top-dress had warmer soils, but the time periods of saturated soil were very short. There was some denitrification, it was most likely limited. Late applications were made to moist soils followed by low humidity dry weather with warm temperatures. Volatilization losses without the use of Agrotian or ammonium thiosulfate could have occurred where rain was limited, dry urea would have been at greater risk than streamed UAN. While conditions indicate that the loss was not excessive the use of soil nitrate and ammonium testing where the condition favored accelerated volatilization, along with wheat tissue tests, may be needed to monitor the crops’ nitrogen needs.

The ALGL Agronomy staff took their own advice and pulled a couple of nitrate samples. Streamed UAN with ammonium thiosulfate and nitropyrin in late application made before a dry spell with low humidity on soil with an elevated pH resulted in approximately a 7% nitrogen loss two weeks after application in the Fort Wayne area. More information on making these determinations cab be found on our blog post "Making Sense of Soil Nitrate and Ammonium Values."

What's in Your Tank?

Not that long ago, creeks, rivers, and ponds were an acceptable source of spray water. This practice seems unthinkable today, given our understanding that products like glyphosate are rendered inactive by clay particles and other impurities in the water. Through research it has been demonstrated that most pesticide chemistries are impacted, often negatively, by the various dissolved minerals and pH of the water used as the carrier.

Weed resistance, rising input costs, the need for effective cover crop kills, increased use of companion products such as foliar fertilizers, along with an increase in spray solution modifying adjuvants reaching the market have increased the need to quantify the quality of water used for pesticide dilution. Currently it is more common to analyze spray water quality after something has gone wrong rather than proactively testing to identify potential problems. 

The stability of pesticides in the spray tank is often directly tied to the pH and the presence of dissolved minerals in the spray water. Depending on the pesticide chemical formulation, the active ingredient can be rendered inactive by either reacting with hydroxyl groups at high pH or with additional hydrogen ions at low pH. These chemical alterations of the active ingredient can also drive chemical reactions with the dissolved solids in the water rendering the pesticide inactive.

Herbicide products like dicamba and 2-4,D amine can be unstable at pH’s above 7.0. Insecticides and fungicides are even more sensitive to spray water pH.  For example, some can be stable in the spray tank for days to months at a water pH of around 5, while at a pH of 9.0 are stable for only minutes. Many of your brand name pesticides that are pH sensitive are buffered in the formulation; however, this is not the case for all generics. Adjuvant manufactures have been addressing this need with a wide array of spray water modifiers to buffer pH concerns and tie up dissolved minerals before they impact the pesticide performance.

Analysis of your spray water will greatly improve the success in identifying the right adjuvant and using the product at the correct rate. The use of ammonium sulfate (AMS) with glyphosate applications is a good example of this. When spraying glyphosate, the label rate for AMS is 8.5 to 17 pounds per 100 gallon of spray water. By testing your spray water, you can pinpoint the rate needed for the application, possibly saving on the cost of excessive AMS while still ensuring adequate product to protect the efficacy of the glyphosate. If you are interested in seeing where your spray water stands, please contact the lab for sampling kits and for more information.

Predictions for Nitrogen from Fall-Applied Sources

The nearly perfect weather conditions during the fall of 2022 lead to one of the most efficient harvest seasons in recent memory. The dry soil conditions provided the opportunity for many producers to apply manure or anhydrous ammonia earlier and on more acres than they would in an average year. Now with planting underway throughout much of the region, growers are beginning to question how much of the nitrogen is still there.

An ideal scenario for retaining fall applied nitrogen is a winter that starts off cold and stays cold with relatively low precipitation. Unfortunately, that was not the case for most of the Eastern Corn Belt. Through the months of February and March, the temperatures were a roller coaster. This is very obvious when viewing the National Weather Service’s monthly ice and snow report for February 2023. Fortunately, we did not have excessive precipitation during this time, but most areas still saw average to slightly above average precipitation. So, what does this mean for nitrogen retention? It means that much of our region has had the potential to experience significant nitrogen loss since last fall. Soil testing for nitrate and ammonium is going to be critical this season for those fields with fall applications. For more information on potential winter losses of nitrogen please visit our article  from last spring.

Pelletized Lime vs. Ag Lime

The agronomy staff at ALGL is often asked what are the differences between pelletized lime and regular ag lime? Which one is better? Which one should I use? Is pelletized lime worth the extra cost?

Let’s start with the similarities between pelletized and al lime. Both forms of lime are a mixture of calcium carbonate and magnesium carbonate. The amount of calcium and magnesium vary based on the limestone mineralogy from which the material was mined. Both forms neutralize acidity through the same chemical reaction.

The differences between the two are the physical properties of each. Ag lime is simply crushed limestone and is comprised of particle sizes ranging from a fine powder to small pieces of gravel. For the lime to work, it must dissolve in the soil solution. The smaller the lime particle, the faster it dissolves and begins to neutralize the acidy. The benefit of having various particle sizes is that the small particles will start the process and the larger particles will continue to work for several years.

Pelletized lime is very finely ground limestone that is mixed with a binding agent and pressed into spherical pellets. The concept behind this is to produce a lime with the ability to react quickly but is easy to apply since it can be spread with any equipment used for spreading traditional fertilizer products.

One of the misconceptions about pelletized lime is that you get the same results as ag lime while using only a fraction of the amount. In the short term, this may be true since it does react faster, but it will also run out much faster. So, over the course of several years, it will take the same amount of lime to manage the soil pH, it just needs to be applied at lower rates more frequently. Typical application rates for pelletized lime usually do not exceed 500 pounds per acre and may only be effective for 1 to 2 years. Whereas an application of ag lime may be as high as 3 to 4 tons per acre in a single application and may effectively manage the pH for 4 to 8 years.

For large scale lime applications, it is hard to justify the additional cost of pelletized lime to completely replace traditional ag lime. However, pelletized lime does have its place in pH management. For small fields and wildlife food plots, where access prohibits a large lime spreader, it is a great fit. For land that may only be secured by a grower for a short period, pelletized lime may provide a short term improvement in soil pH without the long term investment of ag lime. Pelletized lime can also be blended with other fertilizers and be spread in a single application when only a low rate of lime is needed.

When it comes to deciding which form of lime to use, it is not about which form is better than the other. Pelletized lime and ag lime are both good products. It is about selecting the form that fits the situation in which it is being used.

Starter Fertilizer and Crop Injury Potential

Starter fertilizer can be an important part of a crop fertilization program when managed properly.  Nutrients placed in close proximity to the developing plant are readily available for uptake.  Early plant development and crop uniformity is encouraged, which can lead to increased yield and/or lower harvest moisture.   However, there are potential injury risks associated with starter fertilizer that must be managed.

Virtually all fertilizer materials are salts and they need to salts to become plant Available. When they dissolve in the soil they increase the salt concentration of the soil solution.  An increase in salt concentration increases the osmotic potential of the soil solution.  The higher the osmotic potential of a solution, the more difficult it is for seeds or plants to extract soil water they need for normal growth. When a fertilizer referred to as a “low salt fertilizer” it is not that fertilizer has less salt, it means the fertilizer has a low index or low salt impact.

Renewed interest in placing fertilizer in or close to the seed row makes it important to remember that an increase in salt concentration in the fertilizer band can cause seed and seedling injury.  Placing fertilizer at least two inches away from the seed can usually prevent injury.  Excess fertilizer application in a starter band can still produce injury, especially under dry conditions.

The accompanying table shows starter fertilizer application method and rate guidelines from Purdue University.  It should be recognized that these are for “typical” growing conditions.

 Fertilizer Placement and Rate Guidelines - Corn

 2x2 Placement – banded 2” beside and 2” below the seed 

• Sandy soils - maximum of 30 lbs N+K₂O
• Heavier soils - maximum of 60 lbs N+K₂O

 Seed-row – applied in furrow, directly on seed. 

• Sandy soils - maximum of 5 lbs N+K₂O
• Heavier soils - maximum of 8 lbs N+K₂O

 Although university guidelines in the region don’t directly mention sulfur (S), it is a salt and should be included (N+K₂O+S) so that the amount applied does not exceed the limit shown in the table.

 Care should be taken when applying fertilizers (urea, MAP, DAP, UAN, ammonium sulfate, ammonium thiosulfate) that produce free NH₃ in direct seed contact.  Soybeans are especially sensitive, and seed row placement of fertilizer should only be done with extreme caution.

The addition of micronutrients in starters should also be done with caution. Elements like boron, copper, and zinc can be toxic to plants in high concentrations. While the safety tolerance on zinc is quite high, boron and copper can create zones of potentially toxic levels when high rates are concentrated in a band close to the row. This is of greater concern in heavier soils with poor drainage. For example, a common annual broadcast application rate of boron is 0.5 to 1.0 pounds per acre. If that same rate was applied in a 2x2 it would effectively increase the concentration of boron in the band 10 to 30 fold. A 10 pound per acre rate of boron would be toxic to most crops.

A great detailed reference on fertilizer salt index can be found at: https://extension.soils.wisc.edu/wcmc/understanding-salt-index-of-fertilizers-2/

Impact of Manure on Soil pH

A growing issue in the portions of our region is manure applications leading to unexpected or undesirable increases in soil pH. The secondary challenge is that once this issue is identified, and manure applications have been stopped, the soil pH will continue to increase for several more years.

This situation arises with the use of sand bedded dairy manure or layer poultry litter. Often the sand used to bed dairy cows is not actually silica sand, rather limestone (calcium/magnesium carbonate) sand. Any sand passing through separation processes functions the same as course lime.

Layer chicken flocks have calcium carbonate added to their diets to support eggshell formation and avoid calcium deficiencies in the hens. The excess calcium carbonate passes through the digestive track of the bird and feed waste is added to the layer litter. Broken eggs can also be in the litter from accidental breaks in the layer barn. If the layer operation produces liquid egg materials, the eggshells are often added back into the layer litter for land application.

The bedding sand, calcium carbonate feed additive, and eggshells are slow to dissolve and increase soil pH. It often goes un-noticed for several years of application. However once the rise in soil pH is noted, the soil pH will continue to increase for several years after application of the materials has stopped.

The pH increase of these materials is also a very useful tool when used on low pH soils. To better estimate the impact of these manures on soil pH we can test the manures for CCE (calcium carbonate equivalent) the same as a ag lime. While the interpretation of the CCE data is not defined, it does give a relative understanding how quickly and severely the soil pH might increase. For more information on testing the CCE of manures, contact your ALGL regional agronomist.