Organic growing starts with the requirement that plants be grown without the use of chemically altered fertilizers or pesticides, herbicides, or fungicides. The goal of soil based organic growing is the cultivation of soil that will provide adequate gas exchange, drainage and water retention. In addition, the soil should provide optimal conditions for organic content to be processed by earthworms and other beneficial microorganisms into nutrient forms that can easily be used by plants. If and when additional fertilization is needed, organic substances, those that are still in their natural state and have not been through chemical re-composition, are used. These can include substances produced by plants and animals.
In a hydroponic growing system, not withstanding foliar feeding, the water in the system is the sole source of the dissolved minerals and other ingredients that are fed to the plant through the roots. The plants in the system absorb the nutrients they need for growth from the water available in the root environment. A true hydroponic growing system will generally not contain any medium that interacts with nutrients and minerals present in the system’s nutrient solution. Although some gardeners have good results by integrating some
organic components into the otherwise sterile growing medium I do not recommend it, particularly for beginners. The reason is that once solid organic foods are mixed into the growing medium they cannot be taken out and may harbor pathogenic organisms. You can however, adjust, replace and flush your nutrient solution as needed.
The question is whether there can be any overlap between a hydroponics system and an organic system, and the answer is most defiantly yes. Contrary to popular opinion, hydroponic gardens are not limited to chemical fertilizers and it is possible to use organic fertilizer in a hydroponic garden. The chief advantage of hydroponics is the ability to provide optimum levels of water, gas exchange (aeration) and nutrients all at the same time. Although soil has some admirable qualities, particularly for organic gardening, it cannot match hydroponics in those characteristics. It is primarily for this reason that more and more high value greenhouse crops are being grown in hydroponic systems utilizing inert media.
Still, theoretically, it should not be acceptable to produce organic produce without soil, as a living dynamic soil is considered to be the primary component of organic growing. To match this important component of organic horticulture, it is necessary to find a way to introduce beneficial microorganisms into the hydroponics system. Fortunately, by using a passive or re-circulating hydroponics system and inoculating it with the proper combination of beneficial microbes, the growth medium can become a living dynamic environment.
The easiest and least expensive organic hydroponics system to set up and maintain is a hand watered drain to waste system. People often do not realize that hand watering can be one of the simplest hydroponics growing systems. Some consider this type of system to be borderline between true soil and hydroponic gardening, but if you define a hydroponics growing system as one where fertilizer ingredients are in solution in the root environment of the plants, and any solid media in the plant root environment will not significantly interact with the fertilizer in the water of the system, then this system qualifies as true hydroponics.
This system simply consists of a growing container filled with a special combination of inert media (discussed below) and a drain pan for excess nutrient solution to drain out of the containers. This is called a drain to waste system because the nutrient solution is not re-circulated to the plants, but it can be collected from the drain pan and used to fertilize other soil based plants.
Flood and drain systems also work well for this organic hydroponics and have the advantage of a timer to continually re-circulate nutrient solution to the plants on a given interval, generally six times each day. With nutrient film systems, an external sand filter needs to be used to provide a medium where beneficial microbes can colonize due to the fact that with these systems the plants are not grown in growing medium. Although they are getting better all the time, organic nutrient formulations tend to be thicker, even chunkier, than a liquid chemical fertilizer. This characteristic makes a drip application difficult, and aeroponics almost impossible.
The goal for the medium is to help produce an environment where micro-organisms can live and make otherwise unavailable plant nutrients water soluble and thus available to the plants. Some gardeners utilize perlite or peat as the sole medium for flood and drain or drip systems, but for extended water and air retention and for hand watering systems, the recommended options below are more appropriate.
Regardless of which mix is used, it is recommended that approximately three inches of course gravel or expanded clay is placed in the bottom of the growing container to keep the mix from washing out through the drainage holes in the bottom of the container. With this setup, the drainage holes can be placed on the sides of the container 2.5 inches up the sides. This allows a small amount of nutrient solution in the bottom of the container where it can evaporate and be wicked into the medium further extending the time between watering.
Products containing Beneficial Microbes are very useful in expanding the root surface which consequently increases nutrient uptake as well as creating a balanced biology, and an increased concentration of chitin and cellulose recycling organisms. These products are so effective that good ones can start to produce a balanced biology in the non soil media within five minutes of watering with the microbial rich solution. Generally it takes only one application to establish a healthy and flourishing population of beneficial microbes, but for best results they should be used along with nutrient solution with every watering or reservoir change.
Healthy, biological growing environments include both beneficial bacteria and fungi in a wide variety. The beneficial bacteria provide the highest concentration of biological nitrogen, and beneficial fungus is the second highest source. Bacteria and fungi are consumed by the microbial biology contained within the nutrient solution, and are released as nutrients that can easily be taken up by the root system. A full-range of biology significantly reduces the minimum amount of nutrient required for vigorous plant growth, while still allowing for the use of the same level of nutrient as before beneficial microbe inoculation for maximum nutrient uptake.
When adding beneficial microbes, to the system. First, start with a clean, de-chlorinated water source, add in the nutrients, and then inoculate the nutrient solution with a mixture of beneficial microbes. This gives the beneficial microbes a head start and results in a healthy system where any pathogens should be suppressed before plant damage occurs.
Another option for inoculating the nutrient solution with beneficial microbes is to use some form of compost or vermiculture tea. One consideration if this option is chosen is that teas generally must be used soon after brewing is complete. Some varieties may be kept for a maximum of two weeks in a refrigerator after brewing.
Some growers brew tea in a simple set up consisting of a large bucket, small air pump and a nylon stocking to be used as a tea bag. Once most gardeners experience the great results that are possible from using quality compost tea, they generally graduate to professionally designed brewing systems that can produce tea in as little as 24 hours. For small scale growing operations, the products listed above and others may be a better option because small quantities can be mixed as needed. The good news for those interested in brewing and extracting systems is that these systems can be had for as little as $99 and are available for batches from five gallons to 9,000 gallons per day.
In non organic hydroponics, synthetic fertilizers and mineral salts provide the plant nutrients. The plants access the nutrients in water without the facilitation of microbial activity. This generally results in faster growth than with standard soil applications, and a more sterile growing environment. The downside is the increased salt level that is produced by the chemical base of fertilizers. These mineral salts build up, create pH deficiencies, root lock, pathogenic buildups, and cause negative environmental impacts. Fortunately, many reputable hydroponics manufactures including those listed below now produce quality organic hydroponic nutrients.
With the flood-to-waste system, you start with pure (if possible RO filtered) pH adjusted water, properly mixed nutrient solution and beneficial microbes, and use this solution to water your plants. With a quality media mix, plants may only need to be watered every 2-7 days, but make sure not to allow the mix to completely dry between watering. You will quickly learn how much nutrient solution is needed to minimize the amount that drains out the bottom of the growing containers. If a re-circulating system is used, change the reservoir solution each week.
Flushing a crop with plain de chlorinated pH adjusted water for 7-10 days before harvest will improve the aroma and flavor of your produce. In a re-circulating hydroponics system, change the plain reservoir water with fresh water every day for these last days.
Humic and fulvic acids are another consideration for your organic hydroponics system. These are a big part of the good stuff that composting aims to develop in a traditional soil based garden. These complex molecules are formed as organic matter decays, and occur naturally in soils, peat, oceans and fresh waters. Humic acids are the primary extractable component of humic substances. Fulvic acids are also extracted from humic substances and may be more plant active than humic acids due to their higher oxygen content and abundance of carboxyl groups. Humic acids enhance the nutrient richness of soil and they are believed to increases the permeability of plant membranes promoting the uptake of nutrients resulting in stronger, healthier, better producing plants.
Using sugar supplements along with carbon-based fulvic acid and humic acid bring great benefits to your plants with no downside. Some products contain carbohydrates along with fluvic and humic acid or they can be supplemented separately. You may not know this, but the process of photosynthesis is where plants make sugars that are vital to the cellular preparation, to maintain the plants metabolism and vigor. Plants are very good at making the sugars they need, but in the process of photosynthesis large amounts of energy are used. At the same time plants are burning the carbohydrates that are produced for the production of large fruit, vegetables or blooms. By adding organic carbohydrate supplements to the nutrient solution, carbohydrates that have been allocated to the flowering process will be replenished more easily. This will save on the energy your plants would normally use to create those sugars.
Plants use energy to move water and nutrient through cells up to the leaves where through photosynthesis these elements are converted to sugars and starches which are in turn sent back down to the root zone for possible storage. Plants must produce the enzymes necessary to take up these nutrients, minerals, and vitamins. This process also requires energy (sugars and starches) Supplementing these enzymes allows plants to devote more energy for growth and flower/fruit production. Enzymes also play other important roles in plant growth, most notably improving the root zone by creating naturally occurring enzymes and beneficial microbes that keep the root zone free of sickness. Fortunate sophisticated enzyme formulations which contain the proper balance of numerous enzymes are available from many of the same venders who sell beneficial microbe formulations.
Critics of hydroponics claim that the method is too expensive and/or too complex. They also claim that it takes the fun out of gardening and is unaesthetic. The latter claim has some validity. Some gardeners simply like the joys and challenges of working with dirt and are gardening for more than the potential vegetable yield.
However, for people concerned with the economics and yields of urban food production, hydroponics makes a great deal of sense. Soil is cheaper to buy than hydroponic growing medium, but the extra startup cost is offset by the decreased labor of working with the growing medium which generally weighs as little as two percent of the weight of dirt. Furthermore, container soil leaches so readily that repotting, amending with quality compost and/or repeated fertilization are required for strong yields. These things can make the actual cost of feeding container plants grown in soil comparable to the cost for hydroponic nutrients. An additional benefit of hydroponics is that planting densities can be more intensive due to the fact roots do not need to grow as far in search of nutrient in a hydroponics system.
Nick Fraser is a free-lance writer and Garden & Greenhouse contributing editor.