On 18 Jan, 13:33, hammond wrote:
Any tips on avoiding this sort of thing?

http://img228.imageshack.us/img228/3831/dscf2175pv2.jpg

Depends on the cause.
* Did you use a "feed and weed" applicator and miss some strips?
* or over-apply something ditto? It looks like a trundle applicator
where you have overlapped in places.
* are there irrigation lines or drainage tiles burried under the soil?
* was the picture taken at the end of a wet or dry period?
* if dry, did the stripes re-grow after rain?

There's not a lot to go on. The straight lines are obviously a human
issue, and my money would be on mis-handling some sort of lawn
chemicals. can't say a lot more without knowing a lot more.