I recently talked to a gentleman who visited an Amish greenhouse. He mentioned they were pouring vinegar (by the jugs) into the water supply to their plants. What does vinegar have to offer plants?
The only reason I can think of would be as an herbicide (I can't stand the smell on vinegar), but this use is rather hypocritical and has it's fair share of inconsistencies. It also could've been for lowering the pH of the soil (Acetic acid is in low conc. in vinegar).
Actually, there are quite a few reasons they might use vinegar. One would be that their water supply may be quite hard. It seems plants have a very hard time of absorbing nutrients in extremely hard water. (Mine is off the scale above 8.5 for ph) Second, vinegars like old fashioned apple cider vinegar (the kind that is cloudy looking because they don't filter out all the residues and pulp etc) contains a great deal of minerals and other items that are very good for plants. HOWEVER, you do need to significantly water down the vinegar, because vinegar used straight or in too high of a concentration will kill plants very quickly. For evidence, I found the following quote on another web site: I can't find my other quote right now, but I remember reading that the old fashioned type of apple cider vinegar will also encourage and feed beneficial bacteria and other soil organisms - which in turn will better feed your plant. I'm just experimenting this year with using natural materials - non-animal based - as fertilizers. It is quite amazing what you can find out with a little persistent digging online. I am going non-animal because I have a horrible time keeping the critters from digging up all my plants when I use animal based material. I'm glad that happened, or I'd never have discovered the wonders of alfalfa, molasses and even dandelion greens and flowers for steeping a "tea" to feed my plants. It's only been a month or so, but my plants have reacted more positively to this gentle fertilizer than anything I've ever fed them before. But I digress - you asked about vinegar. My point is, if the gentleman is using vinegar and you see he has wonderful plants keep investigating and give it a try yourself. Nay sayers will always be there to tell you "don't bother!" - but until you try it - you just don't know what you're missing. :)
Also - I should have added this yesterday - if anyone has extremely hard water as I do, vinegar might not be the permanent solution. In fact, I have suspicions that if your water is well buffered, it will rebound to its old level some hours after the treatment. My water is like this - and I solved it by pre-filtering it before use. I keep a few fish and learned this in order to make their water appropriate. (My tap water kills them). You first filter the water through a bucket of peat. Instructions are here: http://www.marksfish.me.uk/index.php?option=com_content&task=view&id=63 Depending on your peat and your water, you might lower the ph from 8.6/8.0 to something like 6.0/5.0. The peat will remove many minerals etc. For my fish who need minerals in their water, I then filter a separate batch of water through charcoal (sold for plants) or activated carbon (sold for fish). This seems to remove any nasties like possible contamination of my well water (possible pesticides or fertilizers from farms / lawns). (I don't drink my well water - and I have no authority to do anything about my well - I don't own it) For my fish I mix both peat filtered and carbon filtered water and they thrive, the ph is closer to neutral. In fact, my fish would prefer it a little bit more acidic, but my snails need neutral to avoid shell damage. Their shells start disintegrating in acidic water. For my indoor and outdoor plants I filter all their water through both peat and carbon mixed together - it is on the acidic side, I think between 6.0 and 6.5 last time I checked. Tedious? Yes. But now I grow extremely healthy plants. When using my tap water, I mostly killed plants by a slow and painful death. (And I killed a lot of fish before this too - now I've killed none since going to this method) I am not concerned that my plants water may not contain any minerals after filtering - I feed my plants well - and I'm not relying on anything food-wise being provided by the water itself. Hope this help someone. :)