I've used corn gluten meal at 20 pounds per 1,000 every month throughout the growing season and saw incredible grass growth and no apparent change in weed pressure.

The CGM used by Iowa is the same CGM used in feed lots and bagged at feed stores. You might find it pelletized which makes it easier to apply with a spreader.

Thanks dchall, but the link in the other post connects to an article that claims that the corn meal is somehow processed with a special patented process. I have no idea whether or not it's really different that the regular animal feed corn gluten.

It is different, and a major reason people who use cgm from feed stores say it doesn't work. Because the concentration of protein is not the same.

http://www.gardensalive.com/product/corn-gluten-meal?ai=753

There's no difference. Here's a quote from the patent.

Corn gluten meal is a commercially available material extracted from
corn meal. It is commercially available from many sources such as Grain
Processing Corporation of Muscatine, Iowa, 52761. Generally, as those
skilled in the art know, corn gluten meal is made by drying the liquid
gluten stream separated from corn during corn wet milling processing.
While its composition can vary, it commonly contains about 60% protein
and is rich in xanthophills. It is a mixture of protein, lipid,
carbohydrate and ash material. While corn gluten meal is known, and has
been commercially available, in the past its primary usage has been as a
feed substance for use with broilers, etc.

It is important to note in accordance with the present invention
that the material applied as a preemergence herbicide is corn gluten
meal, not corn meal. Corn gluten meal, as earlier stated, differs
considerably from corn meal in that it is extracted material made by
drying the liquid gluten stream separated from corn during the corn wet
milling processing. Thus, it represents a fortified material in
comparison with corn meal. Corn meal itself has been tried as a
preemergence herbicide for use in the present invention. Corn meal is
somewhat effective, but corn gluten meal is much more effective.

It is not known precisely why corn gluten meal functions
effectively as a natural preemergence herbicide. While applicant does
not wish to be bound by any theory, based upon investigations to date,
it is believed that the corn gluten meal when applied to a soil plot,
selectively stops root development of annual grassy weeds almost
precisely at the time of germination. As a result, as soon as the plant
begins to grow, it will undergo root stress and die. Thus, for some
unknown reason, while the corn gluten meal does not prohibit
germination, it nevertheless does not allow the root structure to
develop sufficient that the weed can grow to a healthy plant. As a
result, it dies from the lack of root growth. It is possible that some
as of yet unidentified allelopathic compound is present in the corn
gluten meal. If this be the case, it may also be possible to isolate the
compound, and use it in a highly fortified manner. Alternatively, such a
compound could be chemically synthesized and used or perhaps even
produced biotechnically by bacterial substances.

There is a later patent where they mixed CGM with citric acid and/or with ammonium sulfate (another acid when moist) to increase the effectiveness. Both of those are chemical compounds yet Dr Christians refers to this as a "natural product."

You can patent anything including this.

Organic lawn treatment and fertilization program

US 6264714 B1

Abstract

A method of treating and fertilizing a lawn
comprising separate applications of corn gluten, 100% poultry manure
organic lawn/plant fertilizer and milky spore organic soil conditioner
in controlled amounts at specific times over a three year period, the
times being early spring, late spring/early summer, mid to late summer
and late fall or about 50 to 60 days apart commencing in early spring
while forsythia is blooming but before lilacs bloom.

So if any of you are doing those things to your lawn, you should be paying royalties to the patent owner. That seems pretty crazy to me.

The Gardens Alive link states the following at the bottom of the page.
Labeling: "Corn gluten meal" sold as animal feed is not the same thing.
It is not licensed by Iowa State, so the university is not compensated
when you buy it; and it often does not contain the right protein
concentration to achieve seed death. I have received many emails from
listeners who thought they were getting a huge break on the price, only
to discover they were simply feeding their emerging crabgrass.

Products
licensed by Iowa State will say something like "pre-emergent herbicide"
on the label, have the correct protein concentration, and carry
complete instructions for proper use. They are more expensive than
animal feed CGM because they use a much higher quality gluten—which
sells at a premium—and the manufacturer pays that fee to the university
to fund research to find more cool stuff like this. Bylaw, animal feed
gluten cannot say anything about herbicidal effects and will not have
directions for any weed-killing use. It also might not work—did I
mention that?

That is pure marketing. The only difference between a bag of Iowa State CGM and animal feed CGM is the $5 license fee to put the marketing materials on it. Corn gluten meal has been made the same way for decades. It was an agriculture waste material - the byproduct of the making of corn syrup, until it was realized to be high in protein and a possible animal feed. You can find corn gluten meal at any feed lot in a giant orange pile...like this one.

I normally don't like Paul Tukey's limited perspective on natural lawn care, but his opinion on CGM mirrors mine.