While it doesn't get dicussed much, quality water is actually an integral part of growing any crop, particularly quality cannabis. Everyone knows that crappy water leads to crappy weed, but how many people really know why? Also, how many people spend money and go to great lengths to set up awesome grow areas with top notch soils and nutes, only to skimp out on the only thing more used by their plant in photosynthesis than light: H20.
I, personally, have always heard that water was important, so I blindly followed some safe rules; I used tap water for much of the plants' lives, but always let it sit out for at least 24 hours to let the chlorine evaporate, always used the cold tap at a slow pace to fill my watering jugs up to avoid rust and heavy metals, and always used distilled water for germination, clones, seedlings, and flushing before harvest. I didn't really know what these minerals, metals, and rust found in tap water do to plants -- and more importantly growing medium -- so I did a little digging, and there's some interesting things I'd like to share, through my weed-minded interpretation. First off, if you use plain tap water that's sat out at least a day, do you check the pH every time? Not only is tap water inconsistent when it comes to pH, but I think many people will find that their tap water is often acidic. Also, as many may already know, organic nutrients release N slowly over time, and as the N breaks down, only N in the form of NH4+ or NO3- can be used by the plant; more has to be fed to make it to to the plant's cells. Furthermore, Nitrogen degrades more readily AND is more easily leached through the soil than P or K, which is why many farmers of other crops intercrop with legumes and other N regenerating crops, to keep organic sources of N available in the soil. Anything other than H20 in the water plays a huge part in retention and displacement of N in the soil.
As we all know, flowering Cannabis LOVES its P. Phosphorus during peak flowering is almost endlessly used by the plant. Plants extract P from the growing medium in the form of orthophosphate ion, such as H2PO4- or HPO4-. Phosphorus is much competed for between soil minerals and the plant's root system, and when P is free in the soil solution, the soil usually wins. Iron oxides, aluminum oxides, and other minerals in the soil latch onto free phosphorus through a process known as "sorption". Once this happens, the P is unavailable for plant uptake. If your cannabis plant's water is full of these oxides, much of the P you're feeding is not making it to the plant. Just the inconsistency of the battle between soil and plant for P would probably confuse the hell out of us growers, as we'd wonder why our plants are so wishy-washy. Also, the heavy metals found in most tap water do not leach out much, so they build up more and more from each watering. The good news is, is that the P builds up, too, as it doesn't leach as well as Nitrogen, but it takes some experience and trial and error to feed different strains how they prefer, as we all know.
Potassium, or "K", is also needed in fairly large amounts, much like N. K is used by all plants for water retention in cells, immunities to diseases and pests, stem strength and rigidity, and can even play a part in how well a plant's fruit(dank weed) ripens and lasts after harvesting. K is easily leached, also much like N, and adding Cal-Mag to cannabis not only gives them Calcium and Magnesium uptake, but this Calcium and Magnesium in the soil also displaces Potassium(K) in the medium. Potassium deficiency makes plants look sickly, and causes leaves to spot, leaf tips to scorch, and the leaves and eventually the plant to weaken and die. Most people don't have too much of a problem with K in Cannabis, but it is nonetheless important.
The point of all my stoned rambling here is that water plays a big part, as it's not only essential to the plant, but for many weed growers it is the vehicle by which they deliver their nutrients. Other elements of the water also play a huge part in how the soil retains these nutrients, and if they're available for plant uptake. With organic farming, there is a lot going on in the soil, and to make sure these organic amendments are retained an used by the plant, our water must be as pure as possible. Until I really looked into it, I had no idea! I'd like to use distilled water all the time, but wouldn't be able to afford it. I may invest in some decent filtration device, just to see if this impacts my grows.
Since this was interpreted and put in my own words, a lot of it may seem like opinion. I can't cite where I got all of the info, as this was a combination of previous knowledge, one of my grow books, and an online source, but much of what I found was on the online source, such as the info on sorption and organic nutrient uptake:
Comments and thoughts are always welcome. I'd like to hear people's water sources and what they think about it in general. Thanks for reading this looong post! Hope it helps!!
Edited by jangel, 16 May 2010 - 04:03 PM.