Formulas, Terms & Laws:
AlboPepper.com is not a science text-book or an online encyclopedia. But since it discusses a variety of topics that involve scientific laws, principles or terms, I thought this page would be a nice place to group explanations that would otherwise distract from my primary pages.
Please do not cite this material as a source in any technical documents or research papers. This is merely a collection of information as it relates to gardening. By all means though, use any ideas discussed here as the basis of a lab experiment!
Conversions & Formulas:
- 1 cubic yard = 27 cubic ft
- 1 cubic ft = 7.48 gallons = 1728 cubic in
- 1 gallon = 4 quarts = 128 fl oz = 3.79L
- 1 quart = 2 pints = 4 cups = 32 fl oz = .95L
- 1 cup = 8 fl oz = 225 ml
- 1/4 cup = 4 Tbs
- 1 Tbs = 3 tsp = 1/2 fl oz = 16 ml
- 1 US gallon water = 8.34 lb
- 1 lb = 16 oz = 453.6 g
- 1 oz = 28.4 g
- 1 square yard = 9 square ft = 1296 square in
- 1 square ft = 144 square in
- Area = Π (3.14) x Radius2
- Circumference = Π (3.14) x Diameter
Terms & Definitions:
SOLVENT: is a substance into which other chemicals can dissolve. In terms of gardening, we're mainly concerned with the "universal solvent" a.k.a. water. Water can dissolve more substances than any other liquid.
SOLUTE: is the substance dissolved into a solvent. There is usually a lesser amount of solute and a greater amount of solvent. Common examples of solutes are sugar or salt, when dissolved into water.
SOLUTION: is a stable, homogenous mixture made up of a solute dissolved into a solvent. The resulting solution is only one phase (ie solid, liquid or gas). If you completely dissolve salt into water, you will observe a liquid only. No floating particles (solids) will be observed. The measure of how much solute is in a solution is its concentration.
SALT: is an ionic compound formed after a base has reacted with and neutralized an acid. Most commonly, people will think of table salt (NaCl). But there are many other salts. You could find many of them in your water and/or soil. For example, sodium fluorosilicate (Na2SiF6) may be added to your drinking water through the process of fluoridation. Tap water may also contain ammonium salts, chloride salts and phosphorus salts.
When your tap water evaporates, those salts and any other solutes will be left behind. Consider what that means each time you add water to your potted plants. Any minerals in your water that your plants don't directly use will remain in the soil. Not a huge deal. But then water again 3 days later. Then again. Then again. How long will it take for mineral and salt concentrations to reach toxic levels?
OSMOSIS: occurs when a solvent of a less concentrated solution passes through a semipermeable membrane and into a solution of higher concentration. The process stops once both solutions have equalized in concentration. This process explains why plants begin to suffer as the salts in a soil begin to build up. As the soil's concentration of solutes increases, its osmotic potential drops, making it difficult for plants to draw up water. Osmosis can also explain why a plant wilts in a drought. The water in its cells flows into the drier (more concentrated) soil. With less water available, the cell membranes collapse. The plant's rigidity is lost & it sags or wilts under its own weight.
TRANSPIRATION: can be compared to evaporation, except it applies specifically to water vapor that escapes from various plant parts. It occurs more so in the leaves than the other parts. When the leaves' stomatas open to take in CO2, water vapor is released at the same time. The evaporation of water has a cooling effect, keeping leaves cool in the hot summer sun. Transpiration also plays another vital role. As the water escapes a plant's leaves, it creates a sort of negative pressure or suction that serves to draw up more water. Capillary forces work along with transpiration to pull water hundreds of feet, against the force of gravity.
CAPILLARITY (capillary action): is what causes a liquid to flow through narrow spaces even in directions that oppose gravitational pull. It results from a liquid's surface tension along with its adhesion to surrounding surfaces. Capillary (wicking) action is a crucial aspect of sub-irrigated planters. Different soil structures will support different ranges of effect.
POROSITY: measures how much empty space is in a material. It is a ratio of empty space to total volume, often stated as a percentage from 0 to 100%. In container gardening, we are very concerned about the effective porosity of a potting mix. This indicates how much water and/or air can be trapped between the soil particles. Perlite is often used in potting mixes to increase porosity.
Laws & Theories:
Liebig's Law of the Minimum: teaches that a plant's growth and health will be limited by the least available nutrient in the soil. So perhaps there is plenty of N, P and K. But if an essential trace element is missing (such as Iron) then the plant will be limited in growth until the deficiency is corrected.
This concept can be expanded beyond the realm of soil nutrients. Factors such as water, air, light and temperature could also become the limiting factor. Ultimately, the plant's own genetic potential would be the final limiter.
This is an important concept for gardeners to grasp. Adding a synthetic 10 10 10 fertilizer may or may not address the needs of an ailing plant. The issue might instead be the lack of a micro-nutrient. Similarly, adding more water to already saturated plants cannot address a lack of sunlight due to localized shade or overcast weather patterns.
Pascal's Law: relates to fluid mechanics. It deals with a resting fluid (liquid or gas) that is in an enclosed system (such as a cup or several connected cups). If pressure is exerted at any point in the fluid, that exact amount of pressure will be transmitted equally throughout the fluid.
This concept explains how hydraulic jacks work and it also relates to the use of siphons (as a result of atmospheric pressure and gravity). A siphon will connect two water reservoirs, allowing water to flow from the higher container to the lower one. The flow stops once pressures equalize, or the water reaches the same elevation in each container.
Should a gardener care? Sure! -If you are working with sub-irrigation and/or water reservoirs. Your water reservoir MUST be placed at a lower elevation than the lowest point of your planter. If it is, the water that wicks into your planter will only be from capillary forces. But if the reservoir is higher, then additional water will flow into your pot, submerging it, until the two containers equalize.