The Elevated Agriculturalist: Water & Nutrients

Joe Veldon 1 Dec 2018

First I’d like to apologize for my absence – turns out bumper crops on both coasts is all-consuming. So now that I’m home and the snow is flying, I thought it a perfect time to talk about water, the unfrozen kind.

There is a unique and somewhat complicated relationship between water and your plants. The better you understand this relationship, the better you’ll be able to properly cultivate them.

Water is known as the “Universal Solvent” because is so easily bonds with other molecules. This bonding happens because of the “H” Hydrogen ions that hang off the end. Known as the sluts of the molecule world, these ions show no loyalty and will readily bond with anything that’s more attractive – i.e. with a stronger ionic pull.

Because of this bonding, water that is taken up by the plant is rarely just the water molecule but more of a collection of many molecules, all bound together via the Hydrogen ion. This is why it’s so important to have your water tested before using it – so you can see what else is in your water. Having a high mineral content gives you what is called ‘hard’ water. Salts are often added to reduce, or ‘soften’ the water.

The water we use is from a well. It has a wide range of minerals present and with the exception of a few seasonal fluctuations is ideal for plant growth. Lots of water sources are not so lucky. Whether from a natural contaminate like Iron or Sulfur or from a municipality adding Chlorine or Fluoride, many sources need to be ‘scrubbed’ of the undesirable molecules.

This is done using a Reverse Osmosis, RO, filter. This filtration system removes all molecules from the water so that you are left with only pure H2O. There are many advantages to this.  The main being that you know the exact amounts of nutrients that are present, because you’ll be adding them yourself. On the down side, because it’s so pure once you add nutrients the pH is often difficult to stabilize.

Water pH is a numeric scale used to specify the acidity or basicity (alkalinity) of an aqueous solution. It’s a logarithmic scale based on the pull of the hydrogen ion. It uses a scale of 0 (acid) – 14 (basic) where 7 is considered neutral. 

Cannabis plants like it just slightly acidic. In soil, I maintain pH levels  between 6.7-6.8, and in hydro solutions I keep it dead on at 6.5.

Water can come out of the ground with different pH values so it’s always important to test your water before applying it to your plants. I like to test my water before I put any fertilizers in it just to see where my base is at. I have a well and depending on the season, or even if we’ve had lots of rain, the water coming into my house fluctuates between 6.4 all the way up to 8.5. If you were to apply water with an 8.5 pH value you’ll do your plants harm!  

Fertilizers have their own pH which interacts with the water it’s being mixed with. So you always want to mix your fertilizer with your water before taking a reading. Digital pH meters run about $100, are easy to use and more accurate than the home test kits that are available.

If you need to adjust your pH back into range there are store bought products you can add to the solution to bring it back into range. You’ll need to use a lot more pH up than you will pH down to move your solution 0.1 points on the pH scale.

Electro conductivity, EC, or specific conductance, of an aqueous solution is a measure of its ability to conduct electricity. EC is a measurement of the total dissolved solids (TDS) which directly relates to the ability of the material to conduct electrical current through it.

This factor influences a plant’s ability to absorb water.  EC is measured in Parts Per Million, PPM. It’s measured using a TDS, Total Dissolved Solids, meter.  Conductivity measurements are a fast, inexpensive and reliable way of measuring the ionic content in a solution.

Temperature of the solution also plays a critical role in the plants overall health. Plants like their water to be similar to room temperature. Too cold will temporarily shock the root system and block the uptake of nutrients. Too hot and you risk permanently damaging the roots cellular structure.

An easy way to acclimate your water to the environment is to draw it into a tub, I use a 55gallon rain barrel, the evening before and let it sit with an air stone in it. The following morning it will be the same temps as the room and ready to have nutrients added.

Plants require water and oxygen to survive. If you keep your root system under water it creates whatisknown as an anaerobic condition. There’s no oxygen available to the root system, so they rot and the plants eventually die.

I like to use an air stone at the bottom of my reservoir to ensure there is adequate Oxygen available in my solutions.  There are hydroponic systems (which we’ll talk about in a later installment) where the root system grows in only super oxygenated nutrient solution.

It’s important to understand how the plant uses water to take up the nutrients it needs.  When rain falls and penetrates the ground’s surface that’s when those loose ‘H’ ions will start hooking up with any number of suitors.  And all the hot ones are there, Nitrogen, Sulfur, Iron etc…

As the water continues into the soil it bonds with the minerals that are present. When this mineral rich water comes in contact with the plants extensive root system, Electro-conductivity helps it to be absorbed. One inside, the plant’s internal pressure and a network of transport tubes called xylem & phloem move the mineral rich water around.

After plants have converted the mineral water into amino acids, proteins and sugars for plant growth the excess is expelled. The remainder of this mineral water is released through the plants leaves via a process called transpiration.

The other way the moisture is released from the plant is through guttation, which is similar but occurs as a droplet of ‘sap’ at the tip of the leaves.

Water is able to move through a plant because of a system of vacuum and pressure that exists in and around the plant. Internal pressure allows the plant to move the nutrient rich solution around the plant.  External pressure surrounding the plant also plays a role in a its ability to uptake nutrients.

When there’s a lot of moisture in the air the relative humidity is high.  This means that there is already lots of water in the air and  less room for the water that is in the plants to escape to.  When the air is dry there is a vacuum surrounding the plant and the internal pressure pushing the water through the plant meets little resistance and has plenty of space to move to.


Water Definitions

Anaerobic –  pertaining to or caused by the absence of oxygen.

Xylem  – a compound tissue in vascular plants that helps provide support and that conducts water and nutrients upward from the roots

Phloem  – the part of a vascular bundle consisting of sieve tubes, companion cells, parenchyma, and fibers and forming the food-conducting tissue of a plant.

Transpiration  the exhalation of water vapor through the stomata.

Guttation –  Guttation is the exudation of drops of xylem sap on the tips or edges of leaves of some vascular plants

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