Need help with lawn!

Does anyone know how long vinegar will affect the ph of soil? We are doing some work on my in-laws house and the backyard is all weeds, no grass. Since we do not want to use any chemicals, poisons, etc. on the weeds, I was thinking about dousing the yard with vinegar to kill the weeds.
I've been looking on the internet, and some sites say that the soil will be affected for 6 months, others say for a few days. I suppose I could do a test spot and see if anything continues to grow, right? If the weeds grow back fairly quickly, that means that the ph is back to normal, and that we could grow grass after we get the weeds killed, right? If we use the vinegar to get the weeds under control, and find the ph of the soil is still off after a couple of months, can that be easily corrected?
Basically we want to kill the weeds along the borders of the yard, and maybe smother with plastic the middle part of the yard that we intend to grow grass on.
Other options are tilling, but that sounds like a pain, and pulling the weeds is not an option, as there are way too many of them. Also, the amount of time we have available to spend on the yard is rather limited.
If anyone knows the answer to the vinegar question, that would be greatly appreciated, and if anyone has any other tips to get the yard under control, I would be forever grateful!
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Last I heard about vinegar for weed control was that to be effective, it had to be a stronger concentration, more like 24%, than what is available at the grocery store, usually 5%. Also, it can change the pH of the soil (temporarily) and doesn't do a good job of killing nasty weeds such as thistles at the root. Here's some interesting info from Iowa State about the use of vinegar for weed control: http://www.weeds.iastate.edu/weednews/vinegar.htm .
Also being an older hippie chick -- think '60's -- I can understand your reluctance to use "chemicals." But keep in mind that even vinegar is a "chemical." What I will assume you're looking for is the least toxic solution to your problem. That said, the most environmentally-friendly method is to cover the ground with something thick enough to block out light and water -- two basic needs for all plants. You could use heavy plastic, layers of newspaper and the like. The 2nd most non-chemical solution is to mow the plants over and over until they do not have enough stored energy left to regrow. That, however, could take a whole summer, depending on the target weed. As far as tilling, it will get rid of whatever weeds are present, but has the disadvantage of bringing weed seeds to the surface, which means new weed plants.
There is a chemical alternative that is not long lasting in the soil, and one of the few things I would consider in terms of herbicides for getting rid of weeds with very little labor -- glyphosate, the active ingredient in RoundUp. It does not persist in the soil (breaks down within a few days), and is absorbed by the plant leaves, tranlocated to the roots where it kills the plants for good. You have to follow the label as to temperature to apply and be very careful not to get it on plants you do not want to get rid of as it is a nonspecific herbicide, meaning that it will kill any plants it is applied to (by the way, the strong solution of vinegar is also a nonspecific herbicide). If you're concerned about losing desirable plants you can apply it by dipping a gloved hand into the solution and wiping it on the plants you don't want or apply it with a sprayer set to stream aimed at the new leaves -- anything but a fine mist.
Suzy in Milwaukee, WI, Zone 5 -- "The way to avoid housework is to live outside." -Sandra Blacksmith, 1901

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Thanks for the info! We're not worried about losing any desirable plants, as the ENTIRE backyard is a weed. Thankfully, the front yard is in good shape. Maybe we'll use RoundUp on the borders, and put down plastic on the rest of the yard.
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Maybe better to use a small paintbrush to do this but regardless, get the heavy rubber gloves made specifically for working with chemicals.
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hippiechick wrote:

You married into the wrong family.
;-)
--

Travis in Shoreline (just North of Seattle) Washington
USDA Zone 8b
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You make laugh! :)
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