Water Tension: A discussion
By: Patrick L. Porch
Within plants, there is a constant need for something so simple yet without it, the plant would die. Water, this miraculous molecule, with its several unique qualities, give rise to such wonderous creations such as towering oaks down to the most miniscule of moss. One of these qualities is water tension which we will discuss by first defining what water tension is, in common terms.
Water adhesion is the force describing the phenomenon of the surface of water being able to withstand a certain amount of force before breaking. This force is different for all types of water, such as hard water possessing a higher surface tension than, say, RO water. This is due, in part, to the ionic forces that are at play within the water itself from the dissolved solids that are floating about in the solution which aid the water in creating these stronger forces. Plants use this water adhesion as do the microbes (bacteria, fungi, etc.) that have evolved alongside plants, to their benefit.
Within the soil food web an interesting interaction occurs with some even more fascinating outcomes between a water solution (your nutrient solution presumably) and the soil particulate (soil, super soil, coco coir, etc.). What is observed is that the water, as it comes into proximity to the soil particulate, will become attracted to these particles and form a type of film around the soil particle, giving the roots and microbial life in the soil food web a much more targeted area as to where they retrieve their food. Which brings up some questions: 1) Is this force constant? As in, can you continuously add water to the particulate attracting an infinite amount? 2) Does the rate of application of the water solution affect the ability of the soil particulate to “pick up” the water solution itself?
The first question should be approached from the angle that of course you cannot add infinite amounts of water to soil, you will run into runoff issues rather quickly. What is significantly more reasonable to assume is that there is a limit, and where that limit lies, this “point of saturation” is where the soil particulate cannot accept any more water reasonably and that this must also mean that the force acted out between the ions, water molecule, and soil particulate have a range of effective values and thusly, the larger the film of water, the lower the force that is being applied to the water keeping it there. With this in mind, it is easy to see how a plant would benefit quite greatly from being kept in soil that was just below the saturation point as they would not have to “pull” the water so much as simply drink it.
The following is a graph to illustrate this relationship between the saturation point and the water adhesion force present.
The second question, which is about the speed or rate of application having anything to do with the capacity of the soil to hold water. To answer this question, we simply look at how rain falls and how the soil interacts with the natural water cycle that the earth creates on its own. Rain, is delivered in countless tiny packages of water that barely disturb the ground if the rain isn’t falling with too incredibly high of numbers. Keeping this information in hand, watering a garden can be a much more efficient and effective event that can dramatically change your plant’s growth rate by keeping it in an optimally moistened environment. How can this be accomplished on a budget however? Several ways work, but a combination of a few different methods tend to work best for most. I personally utilize syringe and pint size watering pitchers to slow water all my plants.
Methods of slow watering your plants while maintaining efficient time usage (approximately 1 quart/90 seconds via hand watering or 1 gallon/6minutes):
- Drip Irrigation
- Syringe watering (200+ cc size syringe)
- Pint or Quart sized watering pitcher
- Drought based irrigation system (Blumat)
The following video provides audio and visual guidance on some of the concepts mentioned above. Utilizing a cheap and efficient syringe watering technique.