Is PI 88788 Working in Your Soybean Fields?

Soybean Cyst Nematode (SCN) is the number one yield-reducing pest in soybeans. Potential yield loss to SCN is expected to rise as more and more populations of SCN overcome the PI 88788 source of resistance. The Peking source of SCN resistance is not near as common as the PI 88788 source but is used in several soybean varieties.

If you want to see how the SCN resistance source in your soybeans is holding up this growing season, you can do an early and late SCN soil test. If the egg count increases substantially between the early and late SCN sample, your SCN resistance source is likely failing.

Here are the 4 steps to this simple test:

Early SCN sample (June): 

  1. Choose a spot in a current soybean field
  2. Collect 8 to 10 0-6″ soil cores taken within the soybean row at that spot
  3. Mark that spot with a flag or GPS so you can get back to that spot to sample later in the season

Late SCN sample (mid to late August): 

4. Go back to the same spot you collected a soil sample from in June and repeat step #2

Once you’ve conducted this simple test, you will get an idea of whether or not the SCN resistance source in your soybean variety is holding up or if it is time to change the resistance source in next year’s varieties. AGVISE completed a field project using a similar procedure in 2019 and 2020. The data showed that the PI 88788 trait was not preventing SCN populations from increasing in some field sites tested in Minnesota. You can read more about our project here.


Data from the AGVISE SCN field project, 2019-2020

A silver bullet for managing SCN does not exist and will likely never exist. Do your due diligence and figure out if your SCN resistance source is working in your own fields.

You can order SCN submission forms from our online supply store here.

Additional resources:

SCN in Iowa: A Serious Problem that Warrants Renewed Attention

Iowa State University – SCN Resources

 

 

 

Soybean cyst nematode: Failing resistance traits, increasing SCN populations

Originally featured in the Winter 2020-2021 AGVISE Laboratories Newsletter

In 2019, AGVISE Laboratories investigated if popular soybean varieties with PI88788 or Peking SCN-resistance traits were effectively providing protection from soybean cyst nematode (SCN) and found that a number of the varieties failed to do so. We expanded the project in 2020 with cooperation from agronomists in west-central Minnesota.

For over 20 years, PI88788 has been the primary SCN-resistance trait in over 95% of soybean varieties. In the past few years, university research is showing that PI88788 is losing its effectiveness at controlling SCN. Detecting SCN-resistant trait failure with the naked eye is impossible, unlike the detection of failed pesticide control, where you can still see a herbicide-resistant weed that is growing vigorously. Therefore, we wanted to demonstrate how you can measure SCN resistance with soil sampling, even though you cannot see it with your naked eye.

In the project, we had 41 soybean fields with SCN-resistant varieties, 35 with the PI88788 trait, and 6 with the Peking trait. In each field, a location was flagged and soil sampled for SCN egg count in early (June) and late (September) parts of the growing season. From June to September, the SCN egg count increased by 4.9 times on average across all 41 soybean fields (individual field reproduction factor ranged from 1.2 to 12.9). In some fields, the high SCN reproduction rate shows that SCN were successfully reproducing on soybean plants and the SCN resistance trait is failling. We also learned that soybean varieties with the Peking trait had much better control of SCN than those with the PI88788 trait. One cooperator from Benson, MN grew both PI88788 and Peking soybean varieties on his farm. He noted a 2.5 bu/acre soybean yield advantage with the Peking soybean variety (56.5 bu/acre) over the PI88788 soybean variety (54.0 bu/acre).

The project showed that SCN soil sampling in the early vs. late growing season was a simple way to detect a failing SCN resistance trait. The simple protocol only takes a big flag to mark the spot, then a set of soil samples in June and September to compare the SCN egg count results.

 

Feed Nitrate Testing in a Drought Year

Drought is an unwelcome but well-known phenomenon on the Northern Plains and Canadian Prairies. Rainfall has been sparse and scattered across the region, and high temperatures exceeding 90 to 100° F (32 to 38° C) have already caused stress to young crops. These same stresses have also wracked pastures, prompting livestock producers to think about alternative feed options for cattle. Believe it or not, we have already received questions from farmers and ranchers about decisions to cut and bale or graze small grain fields for livestock feed.

When drought-stressed annual crops (e.g., wheat, barley, oat, corn) are cut or grazed, producers must exercise caution about livestock nitrate poisoning when feeding these forages. Drought-stressed crops often accumulate nitrate because plant uptake of nitrate exceeds plant growth and nitrogen utilization. Nitrate is usually concentrated in lower plant parts (lower stem or stalk). When livestock, particularly sheep and cattle, ingest forages with a high nitrate content, nitrate poisoning can occur if large amounts of nitrate convert to nitrite in their digestive system.

Dry soil conditions and high soil nitrate levels favor plant accumulation of nitrate. There is one upside to very dry soil conditions: Some soils may not have had enough soil water to convert all nitrogen fertilizer from the ammonium form to the nitrate form, especially if nitrogen fertilizer was applied in a concentrated band that delays nitrification. Therefore, this may limit the amount of soil nitrate available for plant uptake and accumulation. Regardless, there is still variation across the landscape, and a feed nitrate analysis is the best method to assess livestock nitrate poisoning risk.

When collecting plant material for nitrate analysis, collect the plant parts that the livestock will eat. If plant material will be grazed, recall that lower plant parts contain higher nitrate concentrations; monitor grazing height closely. If plant material will be cut and baled, you should collect plant material above the cutter bar height. Alternatively, plant material can be sampled with a hay probe after being baled.

For the fastest turnaround, submit feed materials for nitrate analysis using a plant sample bag. Write “feed nitrate” for crop choice and select “nitrate-nitrogen” as the analysis option. 

AGVISE Laboratories offers next-day turnaround for feed nitrate analysis. Rapid turnaround on nitrate analysis is important for producers debating to cut and bale or graze small grains or corn as livestock feed.  We also provide livestock water analysis, which includes total dissolved solids, nitrate, and sulfate, to assess livestock drinking water quality. Please call AGVISE staff in Northwood, ND (701-587- 6010) or Benson, MN (320-843-4109) with questions about nitrate, feed/hay quality, or water analysis. We can send you sampling supplies if needed.

AGVISE Laboratories Online Supplies Store

Scouting Shorts: Soybean Iron Deficiency Chlorosis (IDC)

As soybean plants emerge and add trifoliate leaves, keep your eyes peeled for soybean iron deficiency chlorosis (IDC). Through the upper Midwest and into the Canadian Prairies, soils with high pH and calcium carbonate pose a special problem for soybean plants and iron uptake. If you encounter soybean IDC, you will start to notice soybean plants with distinct interveinal chlorosis (yellow leaf with green leaf veins) in the newest leaves. The unifoliate leaves typically remain green.

Look for characteristic symptoms of soybean IDC (above photo).

When to scout

Right now! Soybean IDC symptoms begin to appear as soybean plants enter the first- to third-trifoliate leaf stage. You will often see soybean IDC symptoms appear after a period of cool, wet weather.

Where to look

Soybean IDC symptoms are usually confined to soybean IDC hotspots with high carbonate and salinity. Soil pH is not a good indicator of soybean IDC risk because some high pH soils do not have high carbonate or salinity, which are the two principal risk factors. The soybean IDC hotspots often occur on landscape positions with moderate to poor drainage, but soybean IDC symptoms may appear across the entire field if high carbonate and salinity are present throughout the field. High residual soil nitrate-nitrogen can also make soybean IDC worse, so take an extra look at fields that were fallowed last year (e.g. Prevented Planting) and had higher soil nitrate-nitrogen than normal.

What soybean IDC can be confused with

Nitrogen deficiency: Pale green and yellowing is uniform across the entire leaf and veins (not interveinal like soybean IDC). Yellowing appears on older leaves. It is sometimes observed when poor inoculation or delayed nodulation occurs. Look at soybean roots for active nodules (bright pink-red center) or take plant and soil samples to confirm.

Potassium deficiency: Yellowing starts at the outer leaf margin, works its way inward with some brown mottling. Yellowing appears on older leaves during early growth stages and sometimes on upper leaves during pod fill. Take plant and soil samples to confirm.

Soybean cyst nematode (SCN): Aboveground symptoms are virtually invisible during the early growing season. Visual SCN symptoms only occasionally appear in late July or August, or if dry soil conditions occur. Look at soybean roots for small white-colored SCN cysts or take an SCN soil sample including infected root material to confirm.

More information on soybean IDC symptoms, causes, and management: https://www.agvise.com/soybean-iron-deficiency-chlorosis-symptoms-causes-and-management/

Sidedress Corn Using the Pre-sidedress Soil Nitrate Test (PSNT)

As the corn crop begins to emerge, it is time to prepare for sidedress nitrogen applications. Sidedress nitrogen for corn can be applied any time after planting, but the target window is generally between growth stages V4 and V8, before rapid plant nitrogen uptake occurs. Split-applied nitrogen has become a standard practice in corn to reduce in-season nitrogen losses on vulnerable soils, such as sandy and clayey soils. More and more farmers now include topdress or sidedress nitrogen as part of their standard nitrogen management plan. These farmers have witnessed too many years with high in-season nitrogen losses through nitrate leaching or denitrification.

The target timing for PSNT sampling is when corn is 6 to 12″ tall. Twelve-inch corn is often V4 or V5 (like in the picture above). Do not hesitate in collecting soil samples for the PSNT; the target window for sidedress-nitrogen applications in corn is between the V4 and V8 stages. 

Whether your nitrogen management plan includes a planned sidedress nitrogen application or not, the Pre-Sidedress Soil Nitrate Test (PSNT) is one tool to help make decisions about in-season nitrogen. You may also hear this test called the Late-Spring Soil Nitrate Test (LSNT) in Iowa. PSNT is an in-season soil nitrate test taken during the early growing season to determine if additional nitrogen fertilizer is needed. PSNT helps assess available soil nitrate-nitrogen prior to rapid plant nitrogen uptake and the likelihood of crop yield response to additional nitrogen.

The Pre-sidedress Soil Nitrate Test (PSNT), taken when corn is 6 to 12 inches tall, can help you decide the appropriate sidedress nitrogen rate. The PSNT requires a 0-12 inch depth soil sample taken when corn plants are 6 to 12 inches tall (at the whorl), usually in late May or early June. Late-planted corn may not reach that height before mid-June, but PSNT soil samples should still be collected during the first two weeks of June. The recommend soil sampling procedure requires 16 to 24 soil cores taken randomly through the field, staggering your soil cores across the row as you go. All soil cores should be placed in the soil sample bag and submitted to the laboratory within 24 hours or stored in the refrigerator.

You can submit PSNT soil samples using the online AGVISOR program by choosing the “Corn Sidedress N” crop choice and submitting a 0-12 inch soil sample for nitrate analysis. AGVISOR will generate sidedress nitrogen fertilizer guidelines, using the PSNT critical level of 25 ppm nitrate-N (0-12 inch depth). If PSNT is greater than 25 ppm nitrate-N, then the probability of any corn yield response to additional nitrogen is low. If spring rainfall was above normal, then the PSNT critical level of 20 to 22 ppm nitrate-N (0-12 inch depth) should be used. Iowa State University provides additional PSNT interpretation criteria for excessive rainfall, manured soils, and corn after alfalfa.

If the PSNT is taken after excessive rainfall, the soil cores will be wet and difficult to mix in the field. Therefore, it is best to send all soil cores to the laboratory to be dried and ground, ensuring a well-blended soil sample for analysis. Although in-field soil nitrate analyzers have improved over the years, the difficult task of blending wet, sticky soil cores in the field still remains. The only way to get accurate, repeatable soil analysis results is to dry, grind, and blend the entire soil sample in the laboratory before analysis. AGVISE provides 24-hour turnaround on PSNT soil samples. The soil samples are analyzed and reported the next business day after arrival. Soil test results are posted on the online AGVISOR program for quick and easy access. With AGVISE, you get not only great service but also the highest quality data with four decades of soil testing experience.

Pre-Sidedress Soil Nitrate Test (PSNT) resources

Please call our technical support staff if you have any questions on PSNT and interpreting the soil test results for sidedress nitrogen application.

How Much AMS Does Your Spray Water Need?

AGVISE Laboratories Spray Water Analysis

Hard water is a fact of life for those of us in the northern Great Plains and Prairie Provinces. It is why our homes have water softeners, why our well water tastes funny (or delicious), and one reason we need to add AMS (ammonium sulfate) or UAN to our spray tanks to optimize weed control.

When we talk about conditioning “hard water” for herbicide applications, we are preventing dissolved salts (calcium, magnesium, sodium, potassium, and iron) in water from antagonizing, or binding, the pesticide we’re putting in the tank. Dissolved salts bind to weak-acid, salt-formulated pesticides and reduce their efficacy (e.g. glyphosate [RoundUp], growth regulators, ACCase inhibitors [Select, Axial, etc.], ALS inhibitors [Pursuit, Express, etc.], HPPD inhibitors [Callisto etc.], and glufosinate [Liberty]).

A water conditioner like AMS prevents salts in spray water from binding to pesticides. AMS is most often recommended at rates from 8.5 to 17 lb/100 gal spray volume on herbicide labels. This is a wide window, however, and handling dry AMS can be a pain. So, how do you know how much AMS you should add to the tank to overcome antagonism?

A spray water analysis!

An example of an AGVISE Laboratories spray water report

AGVISE Laboratories provides fast and convenient analysis of spray water used for pesticide applications. The Spray Water Analysis package includes calcium, magnesium, sodium, iron, pH, salt, hardness, and SAR (sodium adsorption ratio). The spray water report uses NDSU data to determine the recommended amount of AMS required per 100 gallons of water to overcome antagonism. You will want to test each water source you use for pesticide applications. This information can help avoid problems throughout the spraying season.

Give us a call in either Benson, MN, or Northwood, ND and we will send you a water sample kit. Each kit contains a water collection jar and a sample information sheet. Water sample tests are completed within a week and results are emailed to you, so you have information on your water source right away.

Don’t let salts take away from your weed control this summer – get your spray water tested!

2021 Plant Nutrient Deficiency Troubleshooting Project

Plant analysis is a valuable tool for managing plant nutrients and troubleshooting agronomic problems. Being certain that a specific plant nutrient is causing deficiency symptoms is difficult with visual symptoms alone. Many causal agents unrelated to soil fertility can cause symptoms that appear to be nutrient-related. There are also some plant nutrient deficiencies that are impossible to determine visually so we call them a “hidden hunger.” For troubleshooting situations, you will need a pair of good and bad plant samples, along with good and bad soil samples, to discover the real answer to what is happening in the field (nutrient deficiency or something else).

To help you troubleshoot problem areas and get familiar with plant analysis, AGVISE Laboratories is sponsoring the Plant Nutrient Deficiency Troubleshooting Project in 2021. We are looking to work with 50 to 100 customers this summer who see apparent nutrient deficiency symptoms in one of their fields and want to be involved in this educational project. Volunteering in this project will help you figure out if a problem area in a field is caused by a plant nutrient deficiency or something else. If you want to volunteer, contact one of our agronomists or soil scientists in Northwood (701-587-6010) or Benson (320-843-4109) as soon as you have a problem area you want to troubleshoot for this project. Immediacy is key for good data. The results may be inconclusive if you wait to take plant samples 7 to 10 days after symptoms first appear because new problems can arise.

Once you have spoken with one of our staff and described the problem in your field, we will send you the supplies packet to submit good and bad plant samples, as well as good and bad soil samples (0- 6 inch). If you can provide us with good photographs to aid in the problem diagnosis, we will cover the soil and plant analysis fees (two complete tissue analyses and two complete soil analyses; $151.20 USD retail value).

It is important to catch plant nutrient deficiencies early while you still have time to make a rescue fertilizer application. Take advantage of the AGVISE Plant Nutrient Deficiency Troubleshooting Project and solve those problems the right way… right away.

New Address for AGVISE Laboratories Canada Receiving Facility

The AGVISE Laboratories Canadian Receiving Facility has moved across the street from its former location in Winkler, Manitoba. What this means for customers sending samples to our Canadian Receiving Facility:

  • The new address is 380 Kimberly Rd Winkler, MB R6W 0H7
  • If you’ve dropped off samples at the receiving shed in Winkler, the shed is now across the street in the Winkler Construction parking lot
  • We will be changing the address on all future printings of AGVISE documents, such as Purolator shipping labels
  • If you have pre-printed Purolator shipping labels that have the old address (375 Kimberly Rd), you can still use these. The Purolator delivery professional knows where the shed has been moved to. 

If you have any questions, please give us a call at 701-587-6010.

Protect Nitrogen Fertilizer from Ammonia Volatilization

Recent rain and snow have brought much-needed precipitation to the northern Great Plains and upper Midwest regions. Some degree of drought conditions stretch from Alberta to Iowa, and agronomists and farmers are wondering the best ways to protect spring-applied nitrogen as the planting season continues. 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 fertilizer nitrogen: ammonia volatilization, denitrification, and nitrate leaching. In excessively wet soils, denitrification and nitrate leaching are a concern. However, for spring-applied nitrogen, ammonia volatilization is the main concern with dry soil conditions and unpredictable rainfall 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. With dry soil conditions, this is important to remember because we must balance the need to protect nitrogen fertilizer while conserving soil water for seed germination and emergence.

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.

Practices to reduce ammonia volatilization, in order of most effective: 

  • Apply urea in subsurface bands at least 3 inches below the soil surface. A shallow urea band (1 or 2 inches) 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 is usually needed. 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 any fertilizer. Take a look after you run across the field and you will see white urea granules everywhere. There are soil-applied herbicide incorporation videos from the 1970s that show what a thorough incorporation job really requires.
  • If nitrogen will be broadcast without incorporation, try to time the fertilizer application right before rain (at least 0.3 inch of precipitation). Soils with good crop residue cover (no-till) may require more rain to sufficiently move urea or UAN into the soil surface.
  • 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 university research-proven urease inhibitor is NBPT, available in products like Agrotain (Koch) and its generic cousins. For generic products, 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 breakdown 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 to corn or wheat 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 will want to time the fertilizer application just before a rainfall or consider NBPT to extend the rainfall window.

Resources on ammonia volatilization and urease inhibitors

Nitrogen extenders and additives for field crops, NDSU

How long can NBPT-treated urea remain on the soil surface without loss?, NDSU

Should you add inhibitors to your sidedress nitrogen application?, University of Minnesota

Split the risk with in-season nitrogen, AGVISE

Livestock Manure Sampling and Analysis

As you develop crop nutrition plans for the upcoming year, it is important to include spring manure application in the crop nutrition budget. Manure is an excellent source of plant-available nutrients and offers nice economic savings, especially with high fertilizer prices. When manure is applied properly, you can maximize the nutrient value, reduce nutrient losses, and comply with government regulations.

A proper manure nutrient management plan starts with soil and manure analysis. AGVISE Laboratories provides both soil and manure analysis as routine services to help you develop the right manure nutrient management plan. You might find “book values” with average manure nutrient contents for different manure types, but there is a lot of variability among manure sources from farm to farm. Would you purchase commercial fertilizer without knowing the nutrient analysis? I do not think so! The manure nutrient concentrations vary widely because of dry matter/moisture content, livestock species and age, bedding type, and feed rations. Each year, AGVISE analyzes thousands of manure samples, and the nutrient content range can be very large (Figure 1). A manure analysis is a quick way to know the dollar value in your manure.

Figure 1. Manure nutrient characteristics of manure samples sent to AGVISE Laboratories, 2013-2020. For any nutrient and manure type, there is substantial variability from manure source to source. The box-and-whisker plot represents the median (middle) nutrient content at the thick middle bar, the 50th-percentile range within the box, and the minimum and maximum variability with the whiskers. 

A good manure analysis starts with a good manure sample. Here are a few tips and tricks in collecting a representative manure sample. AGVISE provides manure sample containers at no cost, so please contact us if you need manure sampling supplies.

Solid Manure

Collect several small manure samples using a shovel or pitchfork in the manure pile or bedding area, place in a clean plastic bucket. Avoid the top or edges of the pile where a crust has formed. Mix the bulk sample well, then submit one subsample for analysis in plastic jar (about 1 pint). Store in refrigerator or freezer until shipped. Place in tightly sealed plastic bag to prevent leakage in shipment. Multiple samples may be necessary if the storage area includes manure for different lengths of time.

Liquid Manure

Before sampling, the liquid storage system must be agitated to mix liquid and solids. Collect several samples in a clean plastic bucket. Mix the bulk sample well, then submit one subsample for analysis in a plastic jar (about 1 pint). Store in refrigerator or freezer until shipped. Place in tightly sealed plastic bag to prevent leakage in shipment.

 

Once the manure analysis results are back, you can begin creating a manure nutrient management plant with the soil and manure test results. The soil test results will determine the crop nutrient requirements to maximize crop yield and profitability. Then, subtract the amount of crop nutrients provided in manure, and apply any remaining crop nutrient requirements with commercial fertilizer. A good manure nutrient management plan will help you maximize economic return on manure inputs. In addition, check with local and regional government agencies for any special requirements in your area.

In recent decades, regulation and public concerns have changed the way we handle manure nutrient management. It is a valuable nutrient resource, which when managed properly, can increase profitability, improve soil properties, and protect the environment.

For additional information on manure analysis and land application, these are some helpful online publications. If you have any questions on manure analysis, please contact the AGVISE technical support team.

Manure Sampling and Nutrient Analysis (University of Minnesota)

Step-by-step Manure Rate Calculations (University of Minnesota)

Manure Application Methods and Nitrogen Losses (University of Minnesota)

Manure Management Guidelines and Fact Sheets (Manitoba Agriculture)