Plant Sampling Basics – Sampling, storing, and shipping plant samples

Plant sampling season is in full swing. Agronomists submit plant samples for analysis for a number of reasons: to confirm visible nutrient deficiency symptoms, to detect “hidden hungers”, and to monitor or fine-tune fertilizer plans. For whatever reason you plan to take plant samples, here is a quick refresher on sampling, storing, and shipping plant samples to AGVISE Laboratories.

Sampling

Collecting the correct plant part is critical for interpreting plant analysis results. Make sure to identify the current plant growth stage and follow the directions for that specific crop and growth stage, displayed on the back of the AGVISE plant sample bag. Do you need AGVISE plant sample bags? You can request them here. If you are sampling a crop not listed on the plant sample bag, please call one of our laboratories for instructions.

 

Plant sampling instructions on the back of AGVISE Laboratories plant sample bag. Please use an AGVISE Laboratories bag to submit plant samples for analysis. We send them to AGVISE customers at no charge. Request them here.

Collect the number of plants or leaves indicated in the instructions. This ensures you have a good sample and that we have enough plant material at the laboratory to analyze. About 2 cups of plant material are typically enough.

Roughly 2 cups of plant material (above) are what we require to complete the laboratory analysis.

Storing – Plant Sample Care

  • Brush off excess soil from plant material before placing it in the bag.
  • PLEASE use AGVISE plant sample bags to submit samples. The backside has the required submission form.
  • If you do not have an AGVISE plant sample bag, use a paper bag with holes poked in for ventilation.
  • DO NOT use plastic bags. Plastic bags trap moisture, increasing the likelihood of plant material decomposition during storage and transit.
  • If you are unable to ship plant samples to the laboratory immediately, store them in a refrigerator (do not freeze).
  • It is okay for plant samples to sit outside of a refrigerator in a ventilated bag.
  • Ensure all plant samples have your AGVISE account number in the submitter section. If you do not have an account number, please include your name, phone number, and address on the sample bag.

Shipping – United States Customers

United States customers can send their plant samples to either AGVISE laboratory. Shipping addresses for both are listed at the end of this email. You can ship samples to us via your preferred parcel carrier (e.g. USPS, UPS, FedEx, Spee-Dee, etc.). The sooner the sample arrives at the laboratory after being collected, the better. If you are sending multiple samples together in a box, do not pack samples too tightly in the box; leave room for some airflow.

Shipping – Canadian Customers

Canadian customers can drop off plant samples at any of the four Manitoba AGVISE dropbox locations: Portage la Prairie, Carman, Altona, or Winkler (see location info here). During the summer, the AGVISE route truck picks up samples from these locations on Tuesdays, Thursdays, and Saturdays. It is best to place your sample(s) in the dropbox the night before the route truck is scheduled. As long as the plant sample bag is ventilated, the sample will be okay sitting in the dropbox overnight. Samples dropped off in Winkler and Portage la Prairie can be placed inside refrigerators at the dropbox locations.

If you are located farther away from the Manitoba dropbox locations, please send your plant samples by Purolator ONLY to AGVISE Laboratories, 380 Kimberly Road, Winkler, MB R6W 0H7.

Additional information on sampling, storing, and shipping plant samples to AGVISE Laboratories can be found in the AGVISE Plant Sampling Guide.

Please contact us if you have any questions on plant sampling and analysis or need any supplies.

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.