H2O Hang-ups?

May 8, 2008

H2o Hang-ups? WHETHER STILL PLANNING or in the midst of a hydroponic grow, there are a few things worth spending time familiarizing yourself with in a bid to guarantee your investment in time and money.

Essentially, you can put a plant in a pot full of high-quality compost and keep it watered regularly, and the plant will do the rest — often carrying itself right through until harvest with no need for nutrients at all. With an automated irrigation system you can simply plant and forget. If you have confidence in your compost mix, this is a fine way to grow great-tasting produce.

When growing hydroponically there are a few diff erences the grower needs to take into account to ensure the plant gets everything it needs to not only survive, but thrive and prosper its way to a happy, healthy harvest.

An indoor grower takes over as God in the eyes of the plant, supplying absolutely everything necessary, and in just the right amounts to ensure success. But like everything in life, too much of a good thing soon turns bad and eventually the plants can die as a result of all the kindness bestowed upon them. This is often made worse when things go awry, and the novice grower ends up hurling lotions and potions at the plant in a bid to cure an unknown ailment, instead of dumping the reservoir and refi lling with plain, pH-adjusted water (pH 5.5).

This buys you time when using a method such as NFT, in which things can go seriously wrong very quickly. There’s no more frustrating a time for a grower than when he or she knows that everything the plant could possibly need has been provided, and yet it simply refuses to feed, leaving the plant displaying defi ciencies galore. Even worse if the plant runs into a wilt even though water and nutrients are available!

OSMOSIS
Before getting to grips with our theoretical situation there are a couple of things worth knowing regarding how roots do their stuff , and all will become crystal clear. The fi rst thing to suggest would be fi ring up Google and doing a search for “Osmosis” (with the quotation marks). Roots take up water and nutrients via the process of osmosis. In short, osmosis is the ability of a fl uid or solution to translocate through a semi-permeable membrane, thus equalizing the concentration of the fl uids on either side of the membrane.

If one side of the membrane has a higher concentration of solution than the other, osmosis sorts it out and maintains the status quo by driving the solution from the highest concentration toward the lowest. Science rocks, huh? Just think about the next time you put on your Goretex™ jacket, (Goretex - a semi-permeable membrane that allows sweat and condensation to pass through while keeping the rain out). Your roots work in much the same manner. O kay, that all sounds pretty straightforward, until you run into nutrient lockout.

LOCKED OUT
The passage of nutrients through the semi-permeable membrane is controlled by the relative concentrations of individual nutrient elements on either side of the membrane. In layman’s terms, if you are feeding an excessively higher concentration of magnesium (for example) than that already existing within the roots, osmosis can work against you by “shocking” the roots into thinking the levels of magnesium are too high.

This can cause the plant to attempt to “shed” magnesium by slipping into reverse gear and drawing magnesium away from the roots and into the root mass. Magnesium will be transported the wrong way, out of the roots and into the cubes/slabs (EC/pH rising at runoff?). This condition will quickly manifest itself as a magnesium deficiency. Once the concentration in the solution is lower than that in the roots, the tide changes and the magnesium deficiency is soon cured. But what happens if it isn’t cured?

The passage of water through the semi- permeable membrane is controlled by either the TDS (total dissolved solids) or EC (electrical conductivity) of the nutrient solution. So, if the EC of the solution you’re feeding is excessively higher than the EC currently in the roots, the plant can dehydrate by drawing water out of the roots and into the medium via osmotic action. If using NFT and this proves to be the case, you can run your irrigation pumps 24/7, but the end is nigh through a “dry” wilt unless fast countermeasures are taken.

TAKING THE PLUNGE
But it’s not all doom and gloom, and if NFT was that easy, everyone would be doing it, right?

It’s no accident that the growers who constantly succeed where others fail are generally the ones who take the time to constantly monitor their water quality. By taking regular readings of your pH/EC values from the reservoir, as well as within the cubes/slabs and at runoff , it’s easy to keep track of how your plant is health-wise and you can counteract these readings before any signs of ailing have manifested on the leaves.

Once the system is dialled, there’s not a lot will get close to NFT yield-wise, but initially it can seem like you’re in at the deep end. Keep treading water and hang in there.

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