I have to ask...is anyone out there still using corn gluten as a product to control weeds, or as a crabgrass pre-emergent?
If the answer to this question is "yes", then in my opinion, you are wasting your time and money.
If you want to use it as a fertilizer then be my guest. However, as a control?....forget it.
Lets explore this product further: at 20 lbs per 1,000 square feet, with an average lawn size of 2,500, you have to put down approximately 1 bag @ $35.00 (my cost).
You, as a homeowner, can expect to pay, after you factor in truck, technician, product etc. about twice that plus HST for a small to average sized lawn.
All this from an organic that gives you about 6 weeks of protection and then in mid June when corn gluten has lost the effectiveness you get crabgrass and weeds anyway. It gets even worse if you aerate after the application. Aerating post CG punches holes in the protective barrier you just applied and expedites the process.
You are better off raising your mower height to 3 inches to keep the soil temperature cooler and the lawn shaded instead of using this product. You'll have a better chance of stifling germination and it won't cost you nearly as much.
Once, I too, because there were no alternatives, blew my brains out on corn gluten, in both granular and liquid, only to realize what a cash dump it really was. Needless to say, I have not used it since. Now I concentrate more on overall lawn health and working in conjunction with the homeowner to keep pesky crabgrass from overtaking your lawn.
Corn is already in everything else from fuel to most of the groceries you buy, you can at least have the last say and keep it off your lawn.