The notions of indoor gardening are often accompanied by the term ‘hydroponics’.
This is more often than not a misnomer, and there has been a variable conflict with this association in regards to illicit plant production. Since plants, their effects on environment, and the intrinsic relationship they hold with us as a food source is of utmost importance, it can be of benefit to understand that criticisms due to the insinuations of illicit involvement are in fact baseless. The percentage of people worldwide who engage in honest and beneficial indoor gardening vastly outnumber any illicit activity. House plants, food production green-housing and ornamental flowers such as orchids are among the most globally prevalent uses of indoor gardening.
There are three ways to categorize indoor gardening, and this considers the substrate or growing medium: hydroponics, aeroponics, and terraponics.
Hydroponics is the method of growing plants with a soilless substrate, or water culture. This can be confusing since many definitions of ‘soilless’ includes mediums which the average person would associate with ‘soil’ more than water. Because of the absence of logic regarding this, Hydroguy acknowledges most ‘soilless substrate’ which appears more or less as dirt to be terraponics.
Hydroponics has been used for much longer than western science has acknowledged it, and originally consisted of small floating gardens on lakes in Asia. Hydroponics is a modern feature of food and flower crop production, and many consider it to be a cleaner and more efficient means of growing. Terms for methods of hydroponics include;
• Flood & Drain
• Nutrient Film Technique (NFT)
• Deep Water Culture (DWC)
These are the ‘common terms’ for hydroponics systems. Horticulture defines them somewhat more specifically, such as sub-irrigation or top-irrigation, but these terms are not found in most books and magazines.
Flood & Drain:
Systems using Flood & Drain often include tables or buckets where plants are suspended in clay pebbles, gravel, or rockwool cubes. The tables or buckets are flooded on timers to disperse water (often nutrient solution) over the roots of the plants and growing medium, and then drained out of the tables or buckets for reuse or waste.
Nutrient Film Technique:
NFT is most widely seen as prefabricated or home-built PVC pipe systems where holes are drilled along the length of the pipe for mesh baskets or rubber plugs which suspend plants with the roots concealed within the pipe. Water (or nutrient solution) is pumped through the pipes which contacts the roots, the growing medium such (as clay, gravel, or rockwool) or both. NFT systems are usually designed so the aqueous solution is pumped into one orifice at the top of the apparatus and gravity fed through the pipes, nourishing the roots of the plants, and draining out the bottom for reuse or waste. NFT can also be utilized on flood tables; rather than allowing the tables to fill prior to draining, water (or nutrient solution) is pumped into one end and allowed to drain freely on the other after hydrating the roots and/or growing medium.
Deep Water Culture:
The essence of DWC, or “static solution culture”, is the continual presence of water (or nutrient solution) in which the root system of plants is submerged. The most common apparatus for growing by DWC on a small or hobby scale are flood tables and buckets. In larger production facilities it is more common to use custom water tables that can contain multiple smaller float-tables that hold the seedlings or saplings with their roots suspended in water. Aeration and nutrient circulation are very important in DWC systems as the natural oxygenation which occurs in other hydroponics systems is greatly reduced.
Drip systems vary in many ways, and do not always resemble ‘drips’. The overall theme of a drip system is utilizing irrigation plumbing to distribute water (or nutrient solution) onto the surface of a medium. The aqueous solution can drip continuously, intermittently, or flow freely from an irrigation line. Drip emitters, sprayers, or mist nozzles are often fitted to irrigation line for precise and uniform applications. In true hydroponics drip systems, most commonly utilizing flood tables or buckets, the excess nutrient solution percolates through the clay, gravel, or rockwool and is then reused or wasted.
Aeroponics is the cultivation of plants using air and nutrient rich water vapor as the substrate the roots are suspended in. Typically no other medium is used to support the plant, and the stalk is fitted into a neoprene or other inert and sterile material which is inserted into an aeroponics system. Aeroponics systems have been available since the mid-80’s and can be purchased in an assortment of various forms.
The aeroponics systems, in contrast to hydroponics and soil systems, are not as easy to classify in regards to common home-build apparatus or standard equipment. The common denominator in any aeroponics system is the necessity to deliver small particles of water in vapor form or as small misted droplets; so no matter which aeroponics unit you are looking to purchase or design there will be some or another form of mister jets, hydro-atomizers, or foggers.
The basic premise is that in order for a plant to survive its rhyzosphere must remain moist. Science has evolved from believing that plants require soil to provide food, to realizing that dissolved minerals in water were sufficient for root delivery; and finally to the ultimate control of moisture delivery in the form of vapor which eliminates a lot of potential for pathogenic activity in the water, growing substrate, and even nutrient delivery lines.
The common design of aeroponics systems looks rather like two Rubbermaid containers sealed together at their openings, one upside down on top of the other. Small holes are made on the top of the unit for the “support plug” to fit into, and the plant is submerged into the small hole with the roots concealed. After the mostly superficial outer design is where the aeroponics systems can greatly differ. Some allow a small portion of aqueous solution to remain in the container for humidity and lengthy roots to rest in, others drain the basin completely of excess water dripping from the roots. No matter what details are employed the roots will be entirely or mostly exposed only to air and water vapor so it is extremely important maintenance and checks are done to prevent plant wilting in the case of a pump failure.
Science has adopted the use of aeroponics as a particularly neutral form of growing in order to study different aspects of plant growth. This is because there is a great deal of factors removed in the actual system of growing plants, allowing scientists to isolate what they are researching much easier. Soil and the myriad of biological activity, bio-chemicals, microscopic processes and chain reactions between soil-born pathogens, beneficial organisms, and nutrients can devastate the isolation of any single variable in the growing process. Even the nutrient invested into a soil medium is impossible to trace entirely. Where it goes, if it is precipitated into a salt or is adsorbed onto a particle of humus, or maybe it is leeched; certainly soil can be used to monitor and test a lot of things, but if the effects of particular nitrogen are the objective it is more suitable to use a growing system where nutrients can be applied with precision and minimal loss. Due to the problems with fluid dynamics in low-gravity, and the cumbersome mass of growing substrates, NASA has been researching and developing aeroponics systems for use in Space.
Aeroponics is an ideal form of growing, and certainly the most advanced; but it not without its own issues. The most common aeroponics systems you will see in a garden center or hydroponics store is really only intended for small plants or short-term life plants. The reason being is these units are usually low-pressure aeroponics systems which only mist or fog the region of roots exposed to the water vapor. Once roots become too great a mass the vapor will have a difficult time reaching the inner portions, which can lead to root death and either decrease the production and health of your plant or just outright kill it. High-pressure aeroponics systems have been created to solve this dilemma and most of the larger-scale and industrial aeroponics systems are high-pressure; yet for a home or hobby producer these systems can be well outside of our budget. Low-pressure systems will sometimes then employ partial deep-water-culture by allowing a marginal amount of aqueous solution to remain in the bottom of the container to allow roots more access to moisture.
Prior to the academic acknowledgement of hydroponics, terraponics was known simply as gardening in whatever form; open-field crop, green-housing, gardening, etc. Terraponics is the use of soil as a substrate or growing medium; the simplest most natural form of gardening in the outside world – but what about the inside?
Where hydroponics and aeroponics have clear-cut definable and controllable variables (for the most part), terraponics is highly complex to the point of mysterious, has an unthinkable amount of variables involved, and requires a great deal of effort to be performed indoors with the same factors as outdoors. Our knowledge of plants, minerals, and how to keep a growing medium inert has allowed green-houses and other indoor gardens to produce with few issues; but there is no question that what we call soil in an indoor garden and an outdoor garden are incomparable. In fact it is questionable whether any single person has enough degrees under their belt to cover all the facets of soil and its minerals, micro-flora, micro-fauna, organic compounds, insects; let alone the complex relationship these variables need to have to form what we might consider “balance”. The separation from outdoor dirt farming and indoor gardening is so vast in fact soil-like mediums have been termed as “soilless” to differentiate a mostly inert and sterile substrate from the natural great outdoor soil that’s comparably teeming with life. Peat ‘dirt’, peat moss, coco coir, and composted substrate rich in organics are all termed soilless, absurd as it is on one level, simply because they are man-made compositions of mineral and decomposed organic matter. This element of being “man-made” is not just significant in regards to ground rock and humus content; the entire web of life present in a healthy soil is only made partially present in soilless substrate if a person adds them, and there is no doubt it is impossible to contrive the millions of organisms a biologist may find in a square foot of your backyard.
For the purpose of recognizing the complexities of natural soil it is beneficial to distinguish what is missing in an indoor “potting soil”, yet Grow School differentiates “dirt” as a substrate that can get you dirty from “hydroponics substrate” which can get a person dusty sometimes but is bereft of the distinctly brown humic substance that “dirties” clothing, clogs pumps, and otherwise could be mistaken by a novice as dirt. Terraponics, as far as Grow School is concerned, includes the indoor use of peat, coco, worm castings, silica clay, compost, perlite, and other common ingredients to a “soilless substrate”. (Note: Perlite and some other common soil additives can also be used as a hydroponics medium.)
Terraponics systems employ pots, beds, hanging baskets, or any other suitable container, often with drainage holes in the bottom for runoff. Soil constitution is important for aeration and drainage, as well as cation-exchange, nutrient adsorption, water retention, and pH. Different plants have numerous optimal conditions for their root zones, and the base-line ingredient for your plants medium is dependant on what specie(s) of plant you want to grow. Often looking at the natural environment the plant is found in will give a good idea as to what it will grow most successfully in, yet many varieties will prevail in several mediums. Acid-loving plants might perform best in a bark-mulch medium or peat, where alkaline-loving plants may be more suited to a well limed sandy loam. The combinations of clay, silt, sand, bark, moss, gravel, etc. and organic compounds like worm castings and compost make for a vastly broad range of possible terraponics growing mediums – to optimize your medium to your preferred plant species may take some research, and many indoor gardeners simply opt out of attempting to complicate their dirt-mediums and purchase pre-mixed potting soil.
When trying to concoct the ultimate growing medium it is also important to consider your fertilization methods. Will your substrate quickly leech mineral fertilizers? How often do you have to water? Is there enough humic substance or clay to facilitate cation-exchange? Do you want to enhance your substrate with micro-organisms, and if so how are you prepared to keep them alive? If ignorance is bliss, and complexity is a burden, you’re not alone. The majority of non-casual indoor gardeners keep things as simple, inert, sterile, and non-biological as possible – which is good considering the synthetic fertilizers we use are known to decimate micro-organisms found in healthy biologically-active soil.
The use of the terms “inert” and “sterile” in regards to potting soil are loose terms. They are inert in the sense that biological activity is negligible, and sterile to the degree that “weed seed” should not be present. All soil with any form of organic matter is in a constant state of decomposition, however because of the duration and conditions required this decomposition occurs so slowly that the medium is usually discarded before any changes are noticeable.
Soil is a complex science, and more over the relationship between dissolved minerals, ions, micro and macro-organisms is astounding and far too involved to delve too deeply into here. There are many disputed facets of indoor gardening regarding organics and their availability in the absence of the “web of life” to convert them to nutrients available to a plant, and synthetic fertilizer use along side organics can reduce the beneficial organisms which may otherwise process the organics. Because most people prefer to use pre-mixed potting soil and synthetic or mineral water-soluble nutrients they skip passed a rabbit hole of problems with the trade-off of having to employ more fertilizers, as well as various pesticides to imitate a healthy indoor garden. This practice, though not as sustainable in the long-term is simple, efficient, and still produces a healthy plant irregardless of how entirely unnatural the environment may be.
Soil pathogens can form in potting soil over time no matter how well composted or sterile it is on purchase. Exudates from bacteria and fungi that live on the root system can bond soil particles together creating an anaerobic region that can restrict air and water flow, and attract unwanted pathogens. Soil pests like insect nematodes take advantage of poor soil conditions and a lack of organism balance that is common indoors. Root exudates attract fungi and bacteria, which in turn attract nematodes which feed on them; nematodes are then a food source for shredder arthropods who’s main predator (predator arthropods) are in much lower quantity in an indoor garden, leaving a monopoly inside your soil to the advantage of thrips, mites, and other pests.
On the flip side as an advantage over hydroponics or aeroponics, terraponics grown indoor vegetables often have a much better flavor. The cause of this I can’t say for certain, but there are a lot of peripheral variables to plant health beyond the 13 macro and micro nutrients such as amino acids, organic vitamins, carbohydrates, and an abundance of organic chemicals plants can utilize. Much less is known regarding these compounds and how they assist the development of plant oils, flavanoids, turpines, and vitamins; but many growers believe them responsible for the quality of their products as well as helpers for quantity of yield and overall plant health.
Ease of use
If we were to order the ease of use for these three growing systems we would order as Terraponics, Hydroponics, and then Aeroponics – so long as the Terraponic system strictly employed pre-mixed potting soil and water-soluble or liquid horticultural fertilizers. There is less equipment, less needed to be relatively successful, and it is a medium most people are more comfortable with.
The benefits of hydroponics and aeroponics can not be undermined however, and as a person becomes more comfortable with the multitudes of variables involved in growing in soil the easier the transition into water or air will be.
Benefits and downfalls of Terraponics summarized
Soil is much more forgiving, retains water, does not require a lot of maintenance, and has a natural pH buffer in case a mistake is made with the nutrient solution.
Soil attracts and houses more pathogens; as well bedded plants can transmit or share pathogens quite easily. Soil pH can by critically detrimental to plant health, and is often overlooked or mistaken for a nutrient problem; when soil pH needs correction it can pose difficulty if the plants are overly sensitive to the correction substance.
Benefits and downfalls of Hydroponics summarized
Hydroponics removes the soil-borne pathogen issues from growing, is very clean, and is usually designed to disperse nutrient solutions automatically, reducing labor. Hydroponics allows nutrient uptake to be monitored and can be adjusted without the delay of waiting for soil to dry. Hydroponics requires less water over-all than soil as unused portions of nutrient solution can be reused for several days.
Hydroponics requires equipment that must be cleaned and maintained to operate properly. If a pump breaks down in a Hydroponics system the portion of the garden irrigated by the pump could dehydrate within hours (depending on the system). Hydroponics is highly pH sensitive – if there is a mistake in the pH of the nutrient solution the effects on the plants is very fast and continues to accumulate problems until corrected. Hydroponics often requires a lot of water for circulation. Nutrient solutions must be kept cool to avoid water-borne pathogens such as pythium – once a water-borne pathogen is present in the reservoir it is distributed to all plants. Reservoir chillers are quite expensive. Methods such as DWC require water aeration to prevent anaerobic pathogen growth in the nutrient solution – other Hydroponics systems may use percolation or recirculation to oxygenate the solution.
Benefits and downfalls of Aeroponics summarized
Aeroponics allows the grower to enjoy the Hydroponics experience with less water, smaller irrigation lines, and less chance of forming pathogens in the apparatus the plants are contained in as there is always a persistence of air. Root to root contact in Aeroponics is greatly reduced since plants are neither suspended in soil or water, nor are they momentarily joined by a film or flow of nutrient solution; this reduces the chance of pathogens and disease spreading through-out the crop and allows plants to be grown closer. Aeroponically rooted plants have been found to show less signs of transplant shock that are commonly observed in hydroponics-rooted plants.
Aeroponics utilizes misters, foggers, or atomizers; for this reason there is a limitation on usable nutrients since micron, coagulation, and buildup of carbohydrates and organic compounds must be considered. Aeroponics systems are often low-pressure which limits the size of root zone the system will be optimal for; this limits use to short-lived plants or species with sparse root zones. Like hydroponics Aeroponics is highly dependant on pH of the nutrient solution, and the pumps that deliver it – it is not forgiving and mistakes can lead to much larger failure than terraponics.