Rufus Akinrinlola's original blog post can be found
Scouting for soybean cyst nematode (SCN) is checking to see if your soybean field is infested with SCN, or if your SCN–resistant soybean variety is suppressing SCN reproduction in your field. This activity can be performed starting from 6 weeks of planting to 4 weeks before harvest. During this period, if present, SCN will be actively feeding and reproducing on soybean roots. So they can be easily seen.
To do the scouting, use a shovel to dig up stunted or yellowish soybean plants, digging from 6 to 8 inches away from the plants to ensure digging out both the roots and the soils attached to them, making sure the roots are not cut by the shovel into the soil.
Please note that pulling out soybean plants with your hands would not work when scouting for SCN. Doing this would make most of the roots lost in the ground, and you may find little to no SCN female on the roots since they are withdrawn into the soil in the process of pulling.