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How can the variability in my soil sample results be explained?

(from Dr. Terry Niblack , University of Illinois at Urbana-Champaign & Dr. Pat Donald, University of Missouri)

Soybean cyst nematodes (SCN) are not evenly distributed in a field. For example, in a single field with an average number of eggs of 50,000, the actual number of eggs in any one section of that field might be anywhere from 0 to 100,000. Due to this natural variability in the distribution of SCN, it is very important to take a sample. Some of the questions we've received about this variability in SCN egg counts are given below, along with the answers.


How do I interpret my soil test results?

Soil sampling for the soybean cyst nematode (SCN) has increased dramatically in the last couple of years. Several private soil fertility laboratories have begun to offer SCN soil analysis as a service. As growers continue to increase their sampling for SCN and begin to compare results from various fields and various laboratories, there are six questions that may be asked to help them interpret their soil sample results.


What is the best time to sample for SCN?

If a grower simply wants to sample a field to check for the presence of SCN, I'd recommend sampling the field after soybean harvest. The chances of finding SCN after a soybean crop are greater than sampling after a corn crop because soybeans are a host for SCN. Of course, if the grower discovers SCN in a soil sample taken from a field in which soybeans were just harvested and corn will be grown the next year, he or she also should collect another sample after the corn harvest in those fields if soybeans will be grown again following the corn crop.



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Cyst Tech® products are mixtures or blends of seed from two or more soybean varieties.

According to the company, Cyst Tech® level A (CTA) is a blend of seed of both SCN-susceptible and SCN-resistant varieties and Cyst Tech® level B (CTB) is a blend of seed from two or more SCN-resistant soybean varieties.



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CystX® varieties are soybean varieties with single sources of SCN resistance.

CystX® SCN-resistant soybean varieties were developed by Purdue University scientists from the University of Missouri SCN-resistant soybean variety ‘Hartwig,’ which possessed SCN resistance from the soybean breeding line ‘PI 437654’ (“PI” stands for “plant introduction”).