Spring tissue sampling of winter wheat can be a very useful management tool. The timing of wheat sampling does not correspond to a specific growth stage though. The important factor when determining the appropriate time to sample wheat is that the wheat has broken dormancy and is actively growing again. Generally, wheat will be at a growth stage of Feekes 3 or 4 when this occurs. The appropriate method for collecting wheat samples at this stage is to collect 25 or more whole plants from ½ inch above the soil surface. One of the benefits of early season wheat sampling is to fine tuning a “green-up” nitrogen applications based on the nitrogen content of the plant at Feekes 5 (please visit the Purdue Extension News Release for more information).
Image: Feekes 5 wheat. Source: Kansas State University
Once the plants reach Feekes 6 and beyond, indicated by stem elongation and jointing, only the most recent fully developed leaf should be sampled. The most recent fully developed leaf is the highest leaf on the plant with a fully developed collar. Once the plant begins heading (Feekes 10 and beyond), the flag leaf should be sampled. Generally, 40 to 50 leaves should be sampled at these growth stages.
Accurate plant tissue testing begins with proper sample collection and handling. Make sure to collect the proper plant part for the current growth stage of the crop, and collect the proper number to make the sample. This information can be found on the plant analysis page at algreatlakes.com. Always avoid soil contamination in your plant samples. Package samples in paper bags. If shipping is delayed, store samples in a cool location, but do not freeze. Never include roots with a plant sample. If you have any questions on proper plant tissue sampling, please contact the lab for assistance.