AM trying to track down details of the use of (I think) 3 per cent
sulphuric acid applied as a spray to onion beds to reduce the need
for hand weeding. I think this is an old-fashioned method, but at
least it is organic. Can you help?
per cent sulphuric acid was once used many years ago to control
weeds in onion beds, but the hazards of diluting the concentrated
acid with water were so dangerous its use has been discontinued.
Even if you could get hold of the acid, I wouldn't recommend you
try it. The shape and biological make-up of onion leaves are such
that the acid did not damage them, but it did affect the weeds.
Modern-day organic weedkillers,
like Nature's Way Greenscape, work on a similar leaf-destructive
basis. They are fatty acids and, if applied at strong enough concentrations,
will damage all plants they come in contact with. However, it is
perhaps possible that you may be able to dilute one of these weedkillers
to a point where it may have no effect on onions but still affect
seedling weeds. You could carry out some trials to see if the idea
works, but be prepared to lose some onions! Let me know what happens.
Gardener, Issue 164, 2005, Page 24
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.