RU has a rather low residual availability unless it's been mixed with a surfactant (those "new" lasts-months formulations). It's not very persistent at all.

Unless you're drinking it or breathing it in at or close to time of application (or it's in your water table) it's very little to worry about...especially the amount home gardeners apply.

As long as you are just talking about RoundUp, which is never supposed to be applied to the soil, as opposed to any number of other herbicides...you should be fine.

Did he apply any insecticides or fungicides to the soil?

Most of the chemicals available to home gardeners, like roundup and sevin insecticide, break down within weeks in the soil. If he sprayed round up a year ago, there shouldn't be any glyphosate in the soil, it will have broken down by now.

To get a certification to sell and label your vegetables as "organic" the USDA requires that your soil be chemical free for 3 years. While you probably are not looking for certification, that time frame is a very conservative estimate for how long most of the farm chemicals used today take to break down. With something like Roundup, it's already out of your soil.

The EPA, when it was testing roundup for certification as an acceptable chemical to approve, found that Glyphosate ultimately breaks down into carbon dioxide, and it has a half life of 32 days. Glyphosate first breaks down into AminoMethylPhosphonic Acid, which is not toxic to plants. AMPA then breaks down into CO2 and other inert compounds.

Those studies were performed on regular farm fields, which have 2-3% Organic matter in the soil. With a garden, having more organic matter in the soil means you have more microbial activity, which would break down any chemical and amendment to the soil faster.

Here is a link that might be useful: Roundup

nc-cm & Chris CL - Thank you, thank you! I had been concerned and in a quandry for weeks, and now I am so relieved. I will have a soil test and get going with my planting.

rhizo - Thank you for responding. I'm glad it was only Roundup. So relieved!