John Breker

Troubleshooting Problems with Plant Analysis

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A green growing crop is a delightful sight, and it is used by many people as an indicator of crop nutrient status. If you have fields with some yellow areas or slow growth, these symptoms may indicate a nutrient deficiency. Most commonly, yellow-looking plants may be deficient in nitrogen, sulfur, or both. If detected early, there may still be time for rescue treatment.

Plant analysis is not a magic or foolproof tool, but it can provide useful information in diagnosing problems when combined with soil analysis and good field scouting. During the summer, our technical staff receives many questions from agronomists, crop consultants, and farmers on troubleshooting problems in their fields. The following tips and tricks will help you identify potential nutrient deficiencies early.

Troubleshooting nutrient deficiencies based on visual symptoms can be difficult if symptoms look similar (yellow for nitrogen and sulfur deficiency in the early season) or indistinct (slow growth for phosphorus deficiency). Proper troubleshooting requires you to collect paired plant and soil samples from the area with poor plant growth and an adjacent area with good plant growth. A single plant sample from the poor area is seldom enough information to accurately identify the nutrient deficiency. A soil sample from the same area is needed to determine if the soil nutrient supply is truly lacking or if reduced plant nutrient uptake is caused by another factor (e.g., soil saturation, soil compaction, cool temperature, disease).

With paired plant and soil samples from both good and bad areas, you can compare the results and determine if the symptoms are caused by one or more nutrients or non-soil issues. This comparison is particularly important for secondary and micronutrients that may also reduce plant uptake of other nutrients such as nitrogen, which could otherwise misidentify the deficiency and lead to the wrong corrective treatment (a common problem when only one plant sample is collected). Plant and soil samples should be collected within 7-10 days of symptom development to identify the nutrient deficiency and to have enough time for a rescue fertilizer application if possible. Plant samples collected after this window may be suspect as other issues may develop and confound the results.

The picture below shows patchy yellowing in a spring wheat field during tillering stage. Plant and soil samples (good and bad) determined that sulfur was deficient in yellow areas, and the grower still had options for applying sulfur fertilizer to correct the deficiency. This is a great example of paired plant and soil analysis helping the farmer choose the right corrective action, rather than blindly putting more nitrogen on yellow wheat.

Yellow wheat showing potential sulfur deficiency (upper leaves yellowing first), but there might be soil nitrogen losses too. A paired plant and soil sample is the best way to decide the right corrective action.

Collecting plant and soil samples for troubleshooting nutrient deficiencies:

  1. Collect one plant sample in the area with possible nutrient deficiency symptoms (bad) and one plant sample in an adjacent area (~50 feet) into the crop that looks normal (good).  Collect the correct plant part for that plant growth stage (see instructions on plant sample bag or plant sampling guide).
  2. Collect one soil sample (0-6 inch) from each location where you collected the “good” and “bad” plant samples.
  3. Take photographs of individual plants that show distinct leaf symptoms (not landscape photographs) from each location where you collected the “good” and “bad” plant samples. Keep these photographs for your records; these will help in interpretation of plant analysis results.
  4. Submit plant and soil samples for Complete Nutrient Analysis (also called Option F for soil samples).

If you have fields with areas of poor plant growth, now is the time to collect plant and soil samples to determine if a nutrient deficiency is the issue. The troubleshooting procedure outlined above will help you detect nutrient deficiencies early and decide upon the proper corrective action if needed. To learn more about proper plant and soil sample collection and interpreting reports, please see the resources below.

Plant Analysis Guides
Plant Sampling Guide
Interpreting Plant Analysis Reports 

Soil Analysis Guides
Soil Sampling Guide
Interpreting Soil Test Reports

Brent Jaenisch

Early Summer Grid Soil Sampling

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The interest in early summer topsoil grid sampling (1.0- to 2.5-acres per grid) continues to increase, especially in traditional corn-soybean growing areas. In Minnesota alone, 30-40% of all grid soil samples are now collected in the summer months. The early summer period (late May to late June) is an excellent period of time to collect grid soil samples, instead of waiting until after soybean harvest when workload and time constraints are heavier.

These early summer soil samples are collected from unfertilized soybean fields, and the soil samples are collected when the soybean plants are in early vegetative growth stages while you can travel across soybean fields with ATVs or UTVs without causing unnecessary damage. These are fields that would have been fertilized two years prior ahead of corn planting, and the fertilizer rates were high enough to cover the following soybean crop as well.

The early summer timeframe works well for 0-6 inch soil sampling and analyzing non-mobile nutrients and soil properties. The commonly tested nutrients and soil properties are P, K, Ca, Mg, Na, B, Cu, Fe, Mn, Zn, pH, buffer pH, salts, organic matter, carbonate (CCE), CEC, and base saturation. It is not applicable for 2-ft residual nitrate-N testing, which must wait until after the crop has been harvested. The mobile soil nutrients like nitrate-N, sulfate-S, and chloride should wait for fall soil sampling.

Advantages to early summer grid soil sampling

  • High-quality soil cores with consistent depth (moist and firm soil profile)
  • No more chasing around in the fall trying to soil sample fields that have been harvested and before any fall tillage occurs
  • More time in summer to develop fertilizer management plans with growers
  • Fields can be fertilized immediately after harvest
  • Avoid post-harvest soil sampling rush in the fall
  • More available labor (interns) in the summer timeframe compared to the fall season
  • On-ground assessment of soybean stands, especially if iron deficiency chlorosis (IDC) is observed

You will want to avoid soybean fields that have been fertilized or manured in the fall or spring prior, as the recent fertilizer or manure application can skew soil test results. In these situations, it is best to wait until after the soybean crop has been harvested to collect soil samples in the fall. In small grain production areas, if soybean or pulses will be planted next year (both crops not requiring nitrogen fertilizer), the early summer timeframe can also offer another opportunity to accomplish grid/zone sampling in the early vegetative growth stages of the small grain crop (barley, oat, wheat), just make sure to avoid any fertilizer bands (seed-row or mid-row fertilizer bands).

John Breker

Protecting Spring-Applied Nitrogen Fertilizer from Ammonia Volatilization

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As the spring planting season gets underway, agronomists and farmers are asking about the best ways to protect spring-applied nitrogen. How much nitrogen might I lose if I cannot incorporate it? Does vertical tillage incorporate fertilizer enough? We have compiled some resources to help answer those questions.

There are three ways to lose nitrogen fertilizer: ammonia volatilization, denitrification, and nitrate leaching. In excessively wet soils, nitrogen can be lost through nitrate leaching and denitrification. However, for spring-applied nitrogen, ammonia volatilization is the main concern with dry soil conditions and unpredictable precipitation forecasts.

When you apply ammoniacal fertilizers (e.g. anhydrous ammonia, urea, UAN, ammonium sulfate) to the soil surface without sufficient incorporation, some amount of free ammonia (NH3) can escape to the atmosphere. Sufficient incorporation with tillage or precipitation is needed to safely protect that nitrogen investment below the soil surface.

Ammonia volatilization risk depends on soil and environmental factors (Table 1) and the nitrogen fertilizer source (Table 2). Typically, we are most concerned about ammonia volatilization for surface-applied urea or UAN. It is not easy to estimate how much nitrogen might be lost, and sometimes the losses can be substantial. Although you cannot change the soil type or weather forecast, you do have control over the nitrogen source and application method (Table 2) to protect your nitrogen investment.

Table 1. Relative risk factors for ammonia volatilization
Factor High risk Low risk
Soil pH >7 <6
Soil moisture Moist Dry
Soil temperature >70 °F <50 °F
Rainfall, irrigation Little or none, heavy dew >0.3 inch after N application
CEC (cmol/kg) <10 >25
Soil surface residue >50% residue cover (no-till, pasture, turf) Bare
Application method Surface broadcast Incorporated, subsurface band
Havlin, J.L., S.L. Tisdale, W.L. Nelson, and J.D. Beaton. 2014. Soil fertility and fertilizers: An introduction to nutrient management. 8th ed. Pearson, Upper Saddle River, NJ.
Table 2. Estimated ammonia volatilization for different nitrogen sources, application methods, and rainfall scenarios on soil with pH > 7 (high risk).
Fertilizer source Application method Precipitation after fertilizer application
> 0.5 inch rain within 2 days Little or no rain likely within 7 days
% fertilizer nitrogen lost
Urea or UAN Broadcast 0-20 2-40
Dribble 0-15 2-30
Incorporated 0-10 0-10
Ammonium sulfate (AMS) Broadcast 0-40 5-60
Incorporated 0-10 0-30
Ammonium nitrate Broadcast 0-20 5-30
Incorporated 0-10 0-20
Anhydrous ammonia Injected 0-2 0-5
Messinger, J.J. and G.W. Randall. 1991. Estimating nitrogen budgets for soil-crop systems. In: Follett, R.F., D.R. Keeney, and R.M. Cruse, editors, Managing nitrogen for groundwater quality and farm profitability. SSSA, Madison, WI. pp. 82-214.

Practices to reduce ammonia volatilization for urea or UAN, in order of most effective practice

  • Apply urea in subsurface bands at least 3 inches below the soil surface. A shallow urea band (1 or 2 inches deep) acts like a slow-release anhydrous ammonia band, and nobody should ever apply anhydrous ammonia that shallow.
  • If nitrogen will be broadcast with incorporation, make sure the fertilizer is sufficiently incorporated at least 2 inches below the soil surface to ensure good soil coverage. A chisel plow or field cultivator are good incorporation tools. The popularity of high-speed disks (vertical tillage) has led some people to think that it counts as a meaningful incorporation event. In reality, it just moves soil and crop residue around on the soil surface without really incorporating the fertilizer. Take a look after you run across the field and you will see white urea granules remaining on the soil surface. Do you remember the old soil-applied herbicide incorporation videos from the 1970s? Those classic videos provide great examples of what a thorough incorporation job really requires. NDSU Extension has posted them online: https://vimeo.com/216680310/e843149fdd
  • If nitrogen will be broadcast without incorporation, try to time the fertilizer application right before rain (at least 0.5 inches of precipitation). Soils with good crop residue cover (no-till) may require more rain to sufficiently move urea or UAN into the soil.
  • If no rain is forecasted in the near future, consider applying a urease inhibitor on urea or UAN to provide temporary protection until rain arrives. The active ingredient NBPT has been widely researched and shown to reduce nitrogen losses; make sure the active ingredient rate is 1.3 to 1.8 lb NBPT per ton of urea to ensure effective NBPT activity and protection. NBPT begins to break down after 7 to 14 days. In addition, it is important to remember that nitrification inhibitors like nitrapyrin and DCD do not protect against ammonia volatilization.

These practices should also be considered if you will be applying in-season nitrogen fertilizer later in the summer. It is always best to apply nitrogen below the soil surface, such as injected anhydrous ammonia or coulter-injected UAN, to protect nitrogen fertilizer. For surface-applied urea or UAN, you should time the fertilizer application just before a rainfall or consider NBPT to extend the rainfall window.

The higher ammonia loss potential for ammonium sulfate (Table 2) often surprises people (and we get questions about it). On calcareous soils with high pH, the initial reaction products of ammonium sulfate [(NH4)2SO4] and calcium carbonate (CaCO3) can produce free ammonia, which may be lost if ammonium sulfate is lying on the soil surface. This is a similar reaction process to free ammonia formation with diammonium phosphate (DAP, 18-46-0) applied to calcareous soils. This is why AMS and DAP are not suggested as seed-placed fertilizers on calcareous soils because of the ammonia toxicity risk to seedlings. Please note that urease inhibitors like NBPT will not protect ammonium sulfate from ammonia volatilization.

Helpful resources

Nitrogen extenders and additives for field crops (NDSU) https://www.ag.ndsu.edu/publications/crops/nitrogen-extenders-and-additives-for-field-crops

Should you add inhibitors to your sidedress nitrogen application? (Univ. Minnesota) https://blog-crop-news.extension.umn.edu/2020/06/should-you-add-inhibitors-to-your.html

Split the risk with in-season nitrogen (AGVISE Laboratories) https://www.agvise.com/split-the-risk-with-in-season-nitrogen/

John Breker

Switching More Acres to Soybean?

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The spike in nitrogen fertilizer prices over the past month has prompted many growers to think about switching more acres to soybean in 2026. The high nitrogen fertilizer prices are squeezing the potential profitability of any crop requiring nitrogen fertilizer, such as corn, dry bean, canola, or wheat. The symbiotic nitrogen fixing behavior of soybean is an impressive feat of nature that helps reduce nitrogen fertilizer expenses in farm budgets.

If you do plan to plant more soybean acres in 2026, remember that soybean still has its own crop nutrient needs and removal, like phosphorus and potassium, that cannot be ignored for the soybean crop or across the crop rotation. In addition, iron deficiency chlorosis (IDC) is a common problem in soybean fields across the region, and soybean cyst nematode (SCN) can debilitate and cripple soybean yield now and into the future.

Before you plant soybean on any acre, it is important to have current soil test information for IDC and SCN. These two problems are best managed with the right soybean variety, and there is a nice window before spring planting to collect soil samples.

Soybean Fertility (Phosphorus and Potassium)

Soybean does not respond to phosphorus as dramatically as grass crops like corn or wheat do. Nevertheless, medium to high soil test P is required to achieve good soybean yields. Soybean responds to broadcast P placement better than seed-placed P or sideband P. In no-till regions where soybean is often planted with air drills, seed-placed P or sideband P is often the only opportunity to apply phosphorus in the system. You must pay special attention to seed-placed fertilizer safety with soybean.

Soybean removes far more potassium in harvested seed than canola or wheat. Soybean yielding 50 bu/acre removes about 60 lb/acre K2O, while wheat yielding 80 bu/acre removes only 25 lb/acre K2O. Pay close attention to potassium removal across the crop rotation. After soybean is added to the crop rotation, cumulative crop K removal over numerous years increases greatly, and declining soil test K is observed over time.

Do not place potassium fertilizer with soybean seed; delayed seedling emergence and reduced plant population can occur. Any potassium fertilizer should be broadcasted or banded away from seed.

Soybean Iron Deficiency Chlorosis (IDC)

Soybean is very susceptible to iron deficiency chlorosis (IDC). Soybean IDC is not caused by low soil iron but instead by soil conditions that decrease iron availability and uptake by soybean roots. Soybean IDC risk and severity are primarily related to soil carbonate content (calcium carbonate equivalent, CCE) and worsened by salinity (electrical conductivity, EC). These primary risk factors (carbonate and salinity) can be measured with routine soil testing.

Soybean IDC is common in the upper Midwest, northern Great Plains, and Canadian Prairies, where soils frequently have high carbonate and/or salinity. Within a field, IDC symptoms are usually confined to soybean IDC hotspots with high carbonate and salinity; however, symptoms may appear across a field if high carbonate and salinity are present throughout the field. Soybean IDC severity is made worse in cool, wet soils and soils with high residual nitrate-N. Soil pH alone is not a good indicator of soybean IDC risk because some high pH soils lack high carbonate and salinity, which are the two principal risk factors.

Guidelines for managing soybean IDC

  1. Soil test each field, zone, or grid for soil carbonate and salinity. This may require soil sampling prior to soybean (possibly outside of your usual soil sampling rotation), or consult previous soil test records.
  2. Plant soybean in fields with low carbonate and salinity (principal soybean IDC risk factors).
  3. Choose an IDC tolerant soybean variety on fields with moderate to high carbonate and salinity. This is your most practical option to reduce soybean IDC risk. Consult seed dealers, university soybean IDC ratings, and neighbor experiences when searching for IDC tolerant soybean varieties.
  4. Plant soybean in wider rows. Soybean IDC tends to be less severe in wide-row spacings (more plants per row, plants are closer together) than narrow-row spacings or solid-seeded spacings.
  5. Apply chelated iron fertilizer (high-quality FeEDDHA or FeHBED) in-furrow at planting. In-furrow iron fertilizer application may not be enough to help an IDC susceptible variety in high IDC risk soils (see points #2 and #3).
  6. Avoid planting soybean on soils with very high IDC risk.

Soybean Cyst Nematode (SCN)

Soybean cyst nematode (SCN) is the #1 pathogen causing soybean yield loss in the United States. It is a microscopic parasitic worm that lives in soil and attacks the roots of susceptible soybean and dry bean varieties. Soybean cyst nematode is found across the soybean-growing regions of the United States; it first reached Manitoba in 2019.

Soybean cyst nematode is best managed with crop rotation and SCN-resistant soybean varieties. Soil sampling for SCN is your best tool to learn if you have SCN and also if the SCN resistance traits in your soybean varieties are still working. In recent years, AGVISE Laboratories has documented failing SCN control with PI8878 resistance (most common type) and a continuing increase in SCN egg counts across the region. In some places, the SCN egg counts are so high that no soybean crop (resistant or not) should be planted for multiple years. Once you have it, SCN is nearly impossible to eliminate from fields. A current SCN soil sample will help you choose the right SCN-resistant soybean variety and manage SCN populations now and into the future.

John Breker

USDA-NRCS CEMA 216: A Cost-sharing Program for Soil Health Testing

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Soil health assessment includes more than traditional soil fertility analysis. Soil health encompasses physical, chemical, and biological soil properties, which all come together to provide a healthy, living soil for optimal plant growth. Traditional soil fertility analysis, supported with university research, is still the approved practice for assessing plant nutrient requirements and determining fertilizer rates. Yet, soil health assessment can complement your knowledge and practices to improve soil management.

In January 2026, the USDA-NRCS released an update to Conservation Evaluation and Monitoring Activity (CEMA) 216 – Soil Health Testing. The CEMA 216 program has special soil health testing requirements that AGVISE Laboratories is able and prepared to provide to our clients. The CEMA 216 program focuses on five core soil health measurements and requires water-stable aggregate (WSA) classes, total organic carbon, permanganate-oxidizable carbon (POXC), 24-h CO2 respiration, autoclave citrate-extractable (ACE) protein, soil pH, and soil texture. We have created a soil test package called Option SH216 to meet these requirements. The soil sample collection also requires special instructions and submission forms, which you can find at Resources >> Submission Forms. If you have any questions about soil sample collection and submission for CEMA 216, please contact AGVISE before you collect or ship the soil samples.

Contact your local USDA-NRCS office for more details on CEMA 216, program eligibility, and sign-ups. AGVISE Laboratories also meets the CEMA 216 requirement to choose a laboratory approved through the Performance Assessment Program (PAP) of the North American Proficiency Testing (NAPT) Program.