How to Take Soil Samples for SCN
We’ve mentioned before that soil sampling is key to saving soybean yields from soybean cyst nematode (SCN). But which method should you use, and when should you use them?
There are 2 recommendations for how often to perform soil sampling for SCN: either every 3-5 years or every second or third soybean crop cycle. About the only time not recommended for SCN sampling is when the soil is muddy, as this condition makes the process of egg extraction more difficult.
Depending on what crop was grown previously, growers may want to consider a couple of different schemes for where to take samples from in the field:
- If growing beans after beans, samples should be taken from directly within the harvested crop rows.
- If the previous crop is a non-host, like alfalfa or corn, wait until after the fall tillage and sample irrespective of the row.
With either one of those schemes, sample the top 8 inches of soil. The more soil cores that are taken from an area, the more accurately the SCN level will be represented.
Grid Sampling vs. Conventional Sampling
SCN is not uniformly distributed and shows up in hot spots through fields; because of this, take sub-samples combined from across a field. There are 2 types of soil sampling that can help determine the level of infestation: grid sampling and conventional sampling.
Grid sampling is performed based on the process already in place for soil fertility sampling. Since GPS has enabled much more targeted fertilizer applications, many soil cores are taken from a systematic grid pattern across a field to determine where soil is not as fertile and where it is very fertile. As those cores are pulled for fertility sampling, an extra core or 2 are pulled and kept in a separate bucket. The accumulation of those samples in a composite from across approximately 20 acres is the basis for the SCN sample.
In conventional sampling, the grower would take 15-20 cores in a zigzag pattern from an area that represents about 20 acres or fewer, including areas near waterways, trees or any natural agronomic features of the land. The goal of each sampling method is to collect samples from many areas of the field.
Where to Send Soil Cores for Testing
Soil samples contain biological material, and for that reason, you may not ship soil or plant material across state lines without proper USDA phytosanitary permits. Samples should be sent to the home state’s land-grant university nematode lab.
We recommend that growers stick close with local lab recommendations. Nematode lab websites also contain useful information for growers on management and maintenance, along with sample submission forms for the nematode clinic or lab. You can visit the websites of nematode labs of land-grant universities at the following websites:
- University of Minnesota
- North Dakota State
- University of Nebraska
- Iowa State
- University of Missouri
- Kansas State University
- University of Illinois
- The Ohio State University
- Purdue University
- Michigan State University
- University of Wisconsin
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