I was posed that question yesterday while making a site visit for a future project. Here is a photo of the field:
The answer - The green turf is a tall fescue blend. The brown turf is a combination of crabgrass and goosegrass. This site had 2 frost events in the last 2 weeks. Thus, the crabgrass and goosegrass is turning off color. How much cragbrass is our your field? Maybe a crabgrass preventer is warranted in '13.
To learn more about crabgrass, click HERE to see an article from SportsField Management Magazine.
Go to j-dturf.com to learn more about J&D Turf.