Hi there, I'd like to use a weed killer to clear out all of the weeds in a section of our backyard so that I can later plant grass without having the weeds come back. The most commonly used product for this seems to be Roundup, which I understand contains the chemical glyphosate among other compounds. We have a young daughter who will most likely play in the new grass after it has had a chance to take root for several months. My wife is deeply concerned about the active compounds lingering in the soil and possibly being ingested by our toddler. I have heard that the compounds in Roundup have a relatively short halflife once applied, but I was wondering if you could tell me how much residual glyphosate might remain and for how long and whether any potential residue might pose a significant risk to young children or adults for that matter. Additionally if this method poses significant risk, could you perhaps recommend another method of weed removal that is as effective as Roundup? Thanks! Steve Davis Assistant Professor History Department University of Kentucky
I can provide you the factual information about glyphosate. Ultimately you and your wife will have to decide your comfort level with your daughter from this info. Be aware that using glyphosate will only kill existing vegetation. Immediately afterwards the seed bank in the soil will produce a whole new crop of weeds which will germinate with your grass seed. Often removing the competing grass and exposing the bare ground to sunlight will produce far more weeds that were present in the turf. Many will be annuals and die with cold weather. For the perennial ones,you can use selective herbicides like 2,4-D products once the grass is a few months old.
Here is a link to more information regarding glyphosate.
Hope this is helpful.