Can someone explain to me why dilution rates differ from watering can and bar, versus spraying.?
I'm typically seeing 'x' amount in to 5 litres for watering can and the same 'x' amount into 1 litre for spraying to cover the same area of ground.
For Roundup for instance this area is 20m^2 and I do see difficulty in spraying 1 litre of mixture evenly over that area.
In the end you are putting down the same amount of weed killer for the area, so why the dilution variation?
Rob
The rate at which a pressure sprayer dispenses is much lower volume for a given time than for a watering can and bar, if you made the mix as strong with a can as you do with a sprayer, you'd have difficulty eaking it out at all, let alone evenly.
The spray mist is much finer than a dribble bar drops. To get the same application rate the weedkiller needs to be more concentrated.
You can sometimes do better with a slightly over diluted mixture but it takes longer to do its stuff (better for deep rooted weeds). But if you cut it too fine then it doesn't kill the weeds at all and overuse will get you into the US GM crops bind where they now have several serious and pernicious weeds that are immune to glyphosate due to crass overuse.
Aerosol size and dispersion via wind?
Brian
I suspect that somewhere here I'm missing the point or being (unusually!) thick.
If it takes 20ml of Roundup to treat 20 m^2, then the concentrate of the dilution is unrelated to how the chemical is applied, as long as it all goes evenly over the weeds in the area.
My difficulty is that if I only have 1 litre of mix for a spray, that is going to be quite difficult to spray evenly over a rough area that is 4m x 5m. I see no reason why I can't dilute the spray to say 5 litres, as long as the whole 5l goes on the weeds in the area. I can box off the area and as long as I can see that I have used half the 5l by the time I've done half then I'm doing the job OK - but judging that for only a 1 litre mix would be nigh impossible
Where is my logic going wrong?
Rob
You will find out if you actually try it that 1L in a sprayer goes a long long way. I usually mix about 2L and that is enough to spot weed about an acre of ground (as opposed to complete kill on 20m^2 (which is a 5x4m rectangle and not really all that big).
Generally you find that application with a watering can is a lot more hit and miss and wasteful compared to a weed wand backpack sprayer.
The thing you have to get right is the dose to individual plants. I would not waste glyphosate in a watering can. Some things like PathClear are only suitable for a watering can as too much partially dissolved stuff would clog the jets.
Other thing I found is that it's most cost effective to buy the super-concentrate RoundUp which is a litre bottle at 360gm/litre of glyphosate. Last one took 10 years to get through. Only place I've seen it is B&Q, where they *only* have the empty bottles on the shelf - you have to ask for a full one. Canterbury store had 10 bottles but they all got nicked. Cannabis growers like it, for some reason, so they said.
I spray mine with the nozzel set to a fairly coarse spray - with care (and not doing it in significant wind) it seems to be OK.
It's also worth noting that to kill a plant with glyphosate seems to require most of the foliage is covered. Getting half the plant kills that half of the foliage but does not seem to necessarily kill the whole plant (species dependant).
That was my observation when blatting the weeds in my garden a couple of months back.
Also worth noting that glyphosate:
1) Has a slow "knock down" time - as much as 2 weeks before you can be sure if it actually worked;2) Best bought in concentrated amounts - I got mine from:
You can get it even cheaper if you buy the truely "industrial" version.
Your local agricultural merchant will have it in bulk containers and high strength. I refuse to buy Monsanto branded Roundup because of their arrogant attempt to force GM Roundup Ready crops on the world - any generic glyphosate mixture is just as good.
The funny thing is that US farmers have destroyed the effectiveness of glyphosate in commercial farming in less than a decade as a result.
It is a great shame they have ruined a very good weedkiller by overuse.
Any possible explanation as to why cannabis growers would need it?
I came across some information which might help those interested in experimenting...
I hit my brambles with 8% sol of off-paten Round-Up-alike and nothing happened. Everything else died, but the brambles remaine apparently untouched. In October, a good couple of months later, they all suddenly died off. I mean really died off; dead, Jim.
yep. When i did super dose the same thing happened, except it only took a couple of weeks.
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