While we are finishing family vacations, county fairs, and getting ready to send the kids back to school, it is also time to begin preparing for the fall soil sampling season. As you begin to layout your sampling strategy and processes, please keep the lab in mind.
Planning makes the season go much better for everyone involved. If you find yourself rushed in season to get soil samples collected and then fertilizer recommendations complete, we encourage to you consider sampling a season in advance. For example. If the client spreads fertilizer in the fall, collect the soils sample in the spring so that the recommendations can be made outside of the soil sampling season.
Dry weather this year has stressed the crops enough in many areas. This additional stress has made many underlying issues visible that were normally masked with good growing conditions. Elevated populations of soybeans cyst nematode (SCN) are being found in areas of stunted and yellow soybeans. Especially in light textured soils with a history of frequent soybean crops. Other species of nematodes are impacting corn.
The best time to sample for SCN is in the fall just prior to harvest to determine max population levels in whole field sampling. Diagnostic sampling for SCN focuses samples to be collected in a smaller area where the soybeans are affected during the growing season. This earlier testing may not indicate maximum seasonal population but can identify the location and relative severity of SCN infestations. Collect a minimum of eight 0-8” deep cores near the affected soybean rows to make a composite sample. It is best to collect another sample just outside the impacted area, near the soybean rows, to determine if the injury is due to an isolated population in the field.
When collecting and shipping nematode samples to the laboratory, do so quickly and avoid exposing the samples to extreme temperatures. Overnight shipping is not required. Nematode samples sent to ALGL should request the NCYST test package that will return SCN adult and cyst numbers, along with interpretations of potential percent of yield reduction. For other crops, request the N3 package which is an adult only count of a wide variety of nematodes that impact other crops. This test will also yield an interpretation of crops that maybe impacted by the species of nematodes present.
Not All Nematodes Are the Same - Corn Nematodes
Wheat grain and fertilizer prices have been variable recently. If you are faced with the decision of whether to remove the straw or leave it in the field, take a few minutes to calculate the value of the nutrients that will be removed with the straw. Make sure you are adequately compensated for the replacement costs of these nutrients.
IPNI nutrient removal data shows wheat straw removing 12 pounds N, 3.3 pounds of P2O5, and 24 pounds of K20 per ton. An 80 bushel per acre wheat crop will produce on average 4 ton per acre of straw with a low harvest cut height.
Be sure to calculate the cost to replace those nutrients when pricing the straw product. The cost to replace the P and K removed in the straw is approximately $50 per ton. The replacement cost of the N, P, and K is about $55 per ton. These prices will vary with the fertilizer market. Several factors can affect the actual removal rates such as rainfall following harvest and prior to bailing that will leach a portion of the potassium back to the soil.
If you would like to submit a straw sample to the lab for testing, we can help you more accurately estimate the nutrients removed and your ALGL regional agronomist can help you with the calculations if needed.
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.
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.
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.
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.
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.
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."
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.
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.