How to blend old lawn and new seeded lawn section?

[sixdogs]

Part of my lawn in pretty rough so I am thinking tilling and re-seeding a big section of it---maybe an acre. I have the tools to do it with a big tiller and correct seeder so it's a mechanized process except for doing the edges. I can till a a few feet away from the tree line and edges but I can't get exactly to the edges and will leave a strip and some pockets of old lawn undisturbed.
Do I need to do anything about this or will it blend in over time? Maybe I should over-seed it with some new seed and hope it catches? Any other thoughts and bear in mind I'm really don't wan't to do any hand work with rakes and such. Any advice appreciated.

 

[s219]

I wouldn't even worry about it. I have renovated large sections of lawn, and by late spring of the following year it blends in perfectly. Just make sure you're using the same type of grass of course.

I would not overseed the old section unless it has bare spots, and then only hit those areas. You can accidentally put down too much grass seed in an area, in which case it will suffer in dry conditions and all die (new and old). So keep a good sustainable cover.

I guess the only other factor would be the soil conditions. If you do anything to dramatically alter the soil (amendments, lime, etc) then you would probably notice a difference between new and old sections. If soil compaction is an issue, thoroughly aerate the old section and that will have a better chance blending.