I have actually drilled grass seed and then the same or next day sprayed Round Up and had excellent success with germination.

The half life for glyphosate in soil is typically a month or so depending on conditions.

If you are worried about uptake in the plant you should know that there are glyphosate resistant cultivars of different food crops that are sprayed with Round Up during the growth cycle.

The soil was safe to use 3 years ago.

I have never seen any issues in soil due to Roundup. I kill weeds one day and in a couple days there are more weeds in the same area. Now who knows if there is some unknown effect in the future, but I have so many trees and their mulch circles, with weeds popping up often, I use Roundup and can't imagine life without it.

Here's the deal. On one side you have glyphosate proponents saying that Roundup only lasts a couple days in the soil. On the other side you have detractors saying that it can last for up to a year in soil. Who is right? Both. If you have typical garden soil that is moist then it will degrade quickly. If you live in the Mohave desert that is incredibly arid and you don't irrigate at all, then it can hang around alot longer. But 3 years is right out. It has been gone for a long time.

According to many people the glyphosate does not stay in the soil and does not change soil. However, there is research that shows otherwise. There is also some evidence that the inert ingredients used with the glyphosate causes a synergy that creates more problems,

Here is a link that might be useful: glyphosate in soil

kimmsr, that article about changes in ag soil after years and years of glyphosate use, has little or nothing to do with the OP's question about a single application of glyphosate 3 years ago. Obviously she does not want it in her vegetables so would not continue to use it. I don't see why an article about studies on roundup ready GM crops has to do with her garden.

OP, you have been misled by the reactionaries. That soil was safe to plant in at the time you applied.

Two different points of view are clashing a little bit, and some of it's deliberate. The soil was safe after only a day or less, those three years ago. Safe for plants.

However, it is true that glyphosate and it's breakdown residues can be detected a year later, but that's very rare. Since most applications of the poison are on or neatly at the surface of the ground, the "residue" is subject to weather,. It breaks down very thoroughly in the sun right away and by other means in at most, say, a week or so. Those are highly scientific times! I swear! I read it on the Internet and they can't lie on the Internet.

So, depending on how you look at it, both points are valid in their own specific way.

An arborist I hired to look at my trees said it breaks down really fast - thus if you leave the bottle in the sun, it will lose its effectiveness. She's a super hippy gardener type and said she'd researched it like crazy and in the end felt like it was fine for casual garden use and didn't have long-term effects.

And I agree that the commercial usage of roundup (and the ensuing botanical arms race of resistant crops, resistant weeds, etc etc) is a very separate issue with larger implications for mass food production - but this should be a different (very important imo) discussion.

So, enjoy your garden OP! ;)

"scientia est potentia", knowledge is power. I keep in mind always that the people that want to sell something may not always tell you what you really need to know. There is just too much evidence available that says these glyphosate products are not the benign things the manufacturers and sellers way they are.

Well put slowjane. It is definitely a different discussion.

She's a super hippie gardener type

Well, hell! if she's a SHGT (hey! I resemble that remark!) she must be right! ;)
Actually, I am a SHGT, but have no idea, but I do use round up out of necessity! I live surrounded by horse fields, and there is no "weeding" the yard in the spring!
I do keep the RU out of the raised garden beds and use cardboard during the winter to keep the weeds down.
As soon as it's warm enough and weeks before planting I'll RU the paths around the beds.
If I have something actively growing, I hold cardboard up in the spray area, so not to spray on whatever winter stuff is still growing.
I've neglected my garden while on a 2 week trip to Hawaii, so I may have to do a mid-summer squirt of the nasty stuff just to catch up! Nancy

haha i think SHGT should be a thing....let's start it! lol.

yeah i use SHGTs as a barometer on matters like this I suppose - ;) I'm pretty close to one myself but I have a skeptical streak that keeps me questioning everything so SHGT's are a good counterpoint to the BBS/MG types....

There are different kinds of Round-up, but All of them should be out of your soil after 36+ months.

Safe to eat the plants grown in it? Maybe. But what about the long term health of your soil's rhizosphere? Neat word, eh? Think of it in terms of your plants' gut flora.

I've converted more than one yard from weed killer culture to organic. Regardless of climate, the change is always the same, from heavily compacted clay, poor root systems, opportunistic weeds, impossible to pull out by the roots,...to fluffy dark earthworm rich soil with deep root systems and yet weeds easy to be pulled out by the roots with just a tug. All I did was add a deep layer of mulch and let it break down.

Now I just found an article on some science behind my experience.

Maybe out of desperation, one application of RU isn't a big deal. But if I want to optimize the soil for plants, I'll go with mulch, earth worms, and nitrogen fixing native legumes. If I am eating these plants for nutrition, I don't want to use chemicals that bind with essential minerals, either. That's another story I just found. I'll post it in a follow up.

Here is a link that might be useful: glyphosate effect on rhizosphere

From the article linked:

'Biological
amendment with glyphosate-resistant organisms (Mn reducers and
N fixers) needs further study, as well as more effective means of
detoxifying glyphosate in the rhizosphere. Alternate weed control or
the use of non-systemic herbicides should be considered to minimize
impacts on soil organisms and predisposition to disease.'

None of this is conclusive for me. Whenever scientists are asking for more study, I think they are either not comfortable with the current findings, or they want more grant money.

I feel safest eating vegetables grown on soils known to be organic, including not contaminated by heavy metals, etc.

Sorry if I come across so hair-splitting, but I've had some serious health problems that remained a mystery until I addressed some gut flora and mineral deficiency problems.

Here is a link that might be useful: glyphosate and manganese