When to sample – The ideal time to sample is when the first bloom appears. However, if problems develop prior to bloom, a sample can be taken. Do not sample after the first pods begin to fill.
Sampling at Seedling Stage (6-12”) – Collect all the above ground portion of the plant. Collect 20-30 plants at random from the field or problem area.
Sampling prior to pod filling – Select the first fully developed trifoliate leaf below the top of the plant. The Trifoliate leaf includes three leaves on one stem or petiole. Do not use upper leaves that have not developed to full size. Remove one trifoliate leaf per plant from 30-40 plants selected at random from the field or problem area. Remove and discard stems or petioles as shown in Figure 1.
Figure 1: Pinch leaves from stem or petiole as shown by broken lines.