USDA GIPSA Sampling and Testing Guides
Understanding the quality and condition of your grain is critical, and accurate sampling at many points along the grain chain is necessary to ensure that confidence.
Perhaps the most important aspect of any grain-testing program is obtaining a representative sample from the truck or barge being tested. The USDA has outlined guidelines for effective sampling in a document called Inspecting Grain: Practical Procedures for Grain Handlers.
Section I of the document addresses the importance of proper sampling techniques in order to obtain representative grain samples. They recommend taking at least two probe samples from lots that are 600 bushels or less. For larger lots, draw at least three probe samples. Probe samples should be drawn at random locations from grain sampled at rest, using hand or mechanical probes. Refer to the USDA website for further information on representative sampling methods, techniques and materials.
Once a representative sample is obtained it will be helpful to obtain a smaller yet representative sub-sample for use in the test. A splitter can be used to randomly separate the probe sample(s). By repeatedly taking one of the resulting split samples and re-running it through the splitter, the sample can be reduced to a manageable size for grinding and blending, while still maintaining the representativeness of the original sample.
Alternatively, if using a larger capacity grinder, the entire probe sample can be ground and a representative sample taken from the uniform ground probe sample
USDA/GIPSA has developed a useful tool to assess the probabilities associated with detecting different concentrations of GM varieties in a sample based on different assumptions and sub-sample sizes.
Additional links for USDA GIPSA background documents regarding separating and sampling grain:
Book I, Grain Sampling Handbook, sets the policies and procedures for sampling grain in
accordance with the regulations under the United States Grain Standards Act.
Inspecting Grain: Practical Procedures for Grain Handlers This guidance document can be viewed at the USDA website.