Yes, you are correct, CGM is essentially insoluble, but not completely. What I was referring to was the compounds specifically isolated and related to the herbicidal properties as detailed in the Updated patent: During studies designed to isolate and identify one or more active components of corm gluten we unexpectedly found that hydrolyzed protein from corn gluten provided an effective water-soluble preemergence herbicide that is much more active than the corn gluten meal itself. and the study conducted on corn gluten hydrolysate: Isolation and Identification of Root-Inhibiting Compounds from Corn. Gluten Hydrolysate And in this research summary: If the material is applied too early, weed control is less effective. This is likely due to microbial degradation of the active component of the CGM. And also noted in this article: Making its way to the marketplace: A natural product for the control of annual weeds Continuing field work has shown that rates of corn gluten meal in the range of 20 Ibs./1,000 sq. ft. will reduce crabgrass infestation in Kentucky bluegrass turf by 50 to 60 percent in the first year. As rates are increased, almost total control can be achieved. However, timing is important because microbial activity is known to destroy the activity of the active component. Therefore, it is recommended that the application be made close to the time of weed germination. Moisture is necessary to activate the material, but extended wet periods can reduce its effectiveness, as is the case with synthetic preemergence herbicides.