Well, the clock is ticking. Pretty soon it'll be time to apply preemergent herbicide. I only use organic, natural products on my lawn ever since I had a horrible experience with some synthetic herbicides--and since synthetic chemicals kill the soil's natural, microscopic life like the beneficial bacteria and fungi that your grass depends upon to grow strong. Who wants weed-free grass if your grass isn't strong.
Here's a copy of world-renowned Doctor Nick Christians' instructions for the use of Corn Gluten Meal (CGM) as a preemergent herbicide. Dr. Christians discovered the preemergent qualities of CGM. Thank you Dr. Christians!
HOW TO USE CORN GLUTEN MEAL
Iowa State University
Corn gluten meal works by inhibiting the root formation of germinating plants. It generally does not inhibit the roots of mature plants or transplants until your [sic] reach very high rates (80 pounds/1000 ft2 or higher). It should be applied before germination of the weeds. The weed will germinate and usually forms a shoot, but does not form a root. After germination, a short drying period is needed to kill the plants that have germinated but have not formed a root. Timing is critical. If it is too wet during germination, the plants will recover and form a root. (This is also true of chemical preemergence herbicides).
It is preemergence only, there is no postemergence effect on established weeds. In fact, it makes a great fertilizer for germinated weeds.
If it does not rain in 5 days of application, water it in with approximately 0.25 inches of water. Then leave a drying period after germination.
It will usually work for about 5 to 6 weeks following germination.
[ZoysiaSod's Note: Not sure but maybe Dr. Christians meant to say "following application"--not "following germination?" Or maybe he absolutely meant to say "following germination." It's hard to say. Consider the following passage from Paul Tukey's Organic Lawn Care Manual (Page 179), especially the sentence I highlighted below:
"....[CGM] must be on the ground two to three weeks prior to the expected germination of the target weed. For crabgrass in the North, that date can vary from early April to early May, whenever the forsythia and daffodils begin to bloom. For crabgrass in the South, the product should be applied around mid-March, when the flowers open on dogwood trees. If your target weeds generally emerge in different seasons from crabgrass, corn gluten may be also be [sic] utilized at other times of the year....The product inhibits seed germination of all types and therefore cannot be used within six weeks of overseeding a lawn. That means that in any given spring or fall, you will usually decide not to apply corn gluten but rather to spread new grass seed."
Now consider this quote from David Mellor's Lawn Bible:
"[CGM] should be applied four to six weeks before the time the seeds germinate."
By the way, Mellor's statement differs slightly from Tukey's "two to three weeks prior."
So these three authors raise two different questions in my mind.]
Back to Dr. Christians, the discoverer:
Rates will vary depending on crop and target weed. I generally recommend 20 lbs product per 1000 ft2. This provides about 1 lb [sic: 2 lbs?] of nitrogen per 1000 ft2. Some crops that are grown in rows can be treated in bands in the row and weeds can be tilled between rows. This makes it more economical to use in crop production. Test the material at rates from 10 lbs/1000 ft2 in 10 pound increments to as high as 80 lbs/1000 ft2.
It does not work well with seeded garden crops unless they are seeded deeply (radishes seem to be the exception and there may be others). Transplants or mature plants generally work well. Some producers put down a band, work it into the upper inch of soil, and then put the transplant in the band.
In garden and crop production, growers generally work out their own system, depending on their understanding of the crop they are growing and the weeds they are trying to control.
The material is generally about 10% nitrogen by weight. One hundred pounds has 10 lbs of nitrogen. [ZoysiaSod's note: "That's why I used 'sic' above after 1 lb."]
The nitrogen will release slowly over a 3 to 4 month period after application.