MY USA july aug 2007 - The Planet Fixereco-library.theplanetfixer.org/docs/hydroponics/... · · 2014-12-28Expended perlite can be added to soilless mixes or ... J.B. (2005) Hydroponics:

47MAXIMUM YIELD USA July / August 2007

2. Aeroponic Hydroponic Growing MethodIn an aeroponic hydroponic growing system, the plant roots are

suspended in a fine mist of nutrient solution that is applied on a continuous or intermi�ent basis. Aeroponic growing systems have been described by Soffer (1985, 1988), and commercial details on the method has been given by Adi limited (1982); however, the aeroponic technique has yet to be found economically suitable for the large-scale production of plants (Chow, 2004; Morgan, 2005). Recently, a new home-use growing system, the AeroGarden (see: www.aerogrow.com, and Alexander, 2007) has been introduced that employs the aeroponic method.

Rooting MediaResearchers and growers are experimenting with other rooting

media because rockwool has a significant disposal problem, even though methods are being explored for refurbishing used slabs. Expended perlite can be added to soilless mixes or disposed of by mixing with soil. Coconut fiber (coir), a relatively new rooting medium, is now available in blocks and slabs for use like rockwool blocks and slabs (Morgan, 2003). Various other substances, such as composted bark, sawdust, and rice hulls, have been used in place of perlite and rockwool with varying degrees of success. Some of the physical and chemical characteristics of hydroponic substrates (rooting media) are given in Table 1. (See page 48).A new potential rooting medium, Fytocell, has a number of desir-

able characteristics and is available in slabs as replacements for rockwool, and as loose particles in 50- and 100-L bags for use in BATO buckets. Fytocell is of interest because it is biodegradable, whereas rockwool and perlite are not.

SummaryAlthough both rockwool and perlite hydroponic growing sys-

tems are in wide use, these systems of growing are being studied and modified to make them more efficient in their use of water and nutrient elements, as well as being made adaptable to varying growing environmental conditions (i.e., adaptable to conditions in space, extreme environments, outdoor applications).

48 MAXIMUM YIELD USA July / August 2007

>METHODS OF HYDROPONIC GROWINGTable 1.

CHARACTERISTICS OF INORGANIC AND ORGANIC ROOTING MEDIASubstance Characteristics

INORGANIC

Rockwool Clean, nontoxic (can cause skin irritation), sterile, lightweight when dry, reusable, high water-holding capacity (80%), good aeration (17% air-holding), no cation exchange or buffering capacity, provides ideal root environment for seed germination and long-term plant growth.Vermiculite Porous, sponge-like, sterile material, light weight, high water- absorption capacity (five times its own weight), easily becomes water logged, relatively high cation exchange capacity.Perlite Siliceous, sterile, sponge-like, very light, free-draining, no cation exchange capacity or buffer capacity, good germination medium when mixed with vermiculite, dust can cause respira tory irritation.Pea gravel Particle size ranges from 5 to 15 mm in diameter, free draining, low water-holding capacity, high weight density, which may be an advantage or disadvantage, may require thorough water leaching and sterilization before use.Sand Small rock grains of varying size (ideal size: 0.06 to 2.5 mm in diameter) and mineral composition, may be contaminated with clay and silt particles, which must be removed prior to hydroponic use, low water-holding capacity, high water den sity, frequently added to an organic mix to add weight and improve drainage.Expanded clay Sterile, inert, range in pebble size from 1 to 18 mm free drain ing, physical structure can allow for accumulation of water and nutrient elements, reusable if sterilized, commonly used in pot hydroponic systems.Pumice Siliceous material of volcanic origin, inert, has higher water- holding capacity than sand, high air-filled porosity.Scoria Porous, volcanic rock, fine grades used in germination mixes, lighter and tends to hold more water than sand.Polyurethane grow slabs New material, which has a 75% to 80% air space and 15% water-holding capacity.

ORGANIC

Coconut fiber Made into fine (for germination) and fiber forms (coco peat, palm peat, and coir), useful in capillary systems, high ability to hold water and nutrients, can be mixed with perlite to form medium that has varying water-holding capacities, products can vary in particle size and possible Na contamination.Peat Used in seed-raising mixes and po�ing media, can become wa terlogged and is normally mixed with other materials to obtain varying physical and chemical properties.Composted bark Used in po�ing media as a substitute for peat, available in various particle sizes, must be composted to reduce toxic materials in original pine bark (from Pinus radiata), high in Mn and can affect the N status of plants when initially used, will prevent the development of root diseases.Sawdust Fresh uncomposted sawdust of medium to coarse texture good for short-term uses, has reasonable water-holding capacity and aeration, easily decomposes, which poses problems for long- term use, source of sawdust can significantly affect its accept ability.Rice hulls Lesser known and used, has properties similar to perlite, free-draining, low to moderate water-holding capacity, depending on source can contain residue chemicals, may require sterilization before use.Sphagnum moss Common ingredient in many types of soilless media, varies considerably in physical and chemical properties depending on origin, excellent medium for seed germination and use in net pots for NFT applications, high water-holding capacity and can be easily waterlogged, provides some degree of root disease control.Vermicast/ Composts Vermicast (worm castings) and composts are used for organic hydroponic systems, varying considerably in chemical compo sition and contribution to the nutrient element requirement of plants, can become waterlogged, best mixed with other organically derived materials or coarse sand, pumice, or scoria to alter physical characteristics.

Source: Morgan (2003)



References:Adi Limted (1982) Aeroponics in Israel. HortSci. 17(2):137.Brentlinger, D. (1992) Tomatoes in Perlite: A Simplified Hydroponic System. Amer. Veg. Grower 40:51–52.Chow, K.K. (2004) A New Frontier for Hydroponics. The Growing Edge 16(1):72–75.Cooper, A. (1976). Nutrient Film Technique for Growing Crops. Grower Books, London, England.Cooper, A. (1996) The ABC of NFT Nutrient Film Technique. Casper Publications, Narrabeen, Australia.Day, D. (1991). Growing in Perlite. Grower Digest 12, Grower Books, London, England.Eastwood, T. (1946) Soilless Growth of Plants. Reinhold Publishing, New York, NY.Fischer, D.F., G.E. Giacomelli, and H.W. Janes (1990) A System of Intensive Tomato Production Using Ebb-and-Flow Benches. Prof. Hort. 4:99–106. Gerhart, H.A. and R.C. Gerhart (1992) Commercial Vegetable Production in a Perlite System. In: D. Schact (Ed.). Proceed-ings of the 13th Annual Conference on Hydroponics. Hydro-ponic Society of America, San Ramon, CA., pp. 35–38.Giacomelli, G.E., K.C. King, and D.R. Mears (1993) Design of a Single Truss Tomato Production System (STTPS). Sym-posium on New Cultivation Systems, Cagliari, Italy.Jensen, M.N. (1997) Hydroponics. HortScience 32(6):1018–1021.Jones Jr., J.B. (2005) Hydroponics: A Practical Guide for the Soilless Grower. CRC Press, Boca Raton, FL.Morgan, L. (2002) Ra� System Specifics. The Growing Edge 14(2):26–38.Morgan. L. (2003) Hydroponic Substrates. The Growing Edge 15(2):54–66.

Morgan, L. (2005). Build-It-Yourself Hobby Systems: Drip and Aeroponic Systems. The Growing Edge 16(4):46–53.Papadopoulos, A.P. (1991) Growing Greenhouse Tomatoes in Soils and in Soilless Media. Agricultural Canada Publica-tions 1865/E. Communications Branch, Agriculture Canada, O�awa, ON, Canada.Parker, D. (Ed.) (1994) The Best of the Growing Edge. New Moon Publishing Company, Corvallis, OR.Resh, H.M. (2001) Hydroponic Food Production, 6th Edi-tion. Newconcept Press, Mahwah, NJ.Roberts, W.J. and D. Specca (1997) The Barlington County Research and Development Greenhouse. In: R. Wĳnarajah (Ed.). Proceedings of the 18th Annual Conference on Hy-droponics. Hydroponic Society of America, San Ramon, CA. pp. 19–27.Rorabaught, P.A. (1995) A Brief and Practical Trek Through the World of Hydroponics. In: M. Bates (Ed.). Proceedings of the 16th Annual Conference on Hydroponics. Hydroponic Society of America, San Ramon, CA. pp. 7–14.Savage, A.J. (Ed.) (1985) Hydroponics Worldwide: State of the Art in Soilless Crop Production. International Center for Special Studies, Honolulu, HI.Smith, B. (1994) The Short History of NFT Gully Design. The Growing Edge 15(3):79–82.Soffer, H. (1985) Israel: Current Research and Developments. In: A.J. Savage (Ed.). Hydroponics Worldwide: State of the Art in Soilless Crop Production. International Center for Special Studies, Honolulu, HI. pp. 123–130.Soffer, H. (1988) Research on Aero-Hydroponics. In: Proceed-ings of the 9th Annual Conference on Hydroponics. Hydro-ponic Society of America, Concord, CA. pp. 69–74.Van Pa�en, (1992) Hydroponics For the Rest of Us. The Growing Edge 3(3):24–33, 48–51.

Definitions:Electrical Conductivity (EC):a measure of the electrical resistance of water, nutrient solution, or effluent from a rooting medium, used to determine the level of ions in solution and the potential effect of ion concentra-tion on plant growth; the units commonly used are either millimho per centimeter (mmho/cm) or decisiemen per meter (dS/m).

>METHODS OF HYDROPONIC GROWING


Controlling Climate Conditions

Climate Control — A Must for Indoor GardeningBy indoor gardening we mean growing plants in a closed and

controlled environment. This concept of closed and controlled environment also applies to greenhouses or any grow-room size, whether a closet or a warehouse. In any of these situations, the grower wants to optimize growing conditions to maximize the plants’ yield, thus maximizing the dollar return on the investment and operating costs.Plants need light, water, nutrients, and other materials drawn

from the gas mixture we call “air” to build the vegetal cells through photosynthesis. For the light part, plants are simple: when there is light (light intensity and quality are important) plants feel it’s daytime, and photosynthesis can operate regardless of the hour shown on the clock. When it’s dark, plants feel it’s night and time to complete the tissue-building process and expel byproducts or surplus. This night or dark period of a minimal duration is very important and plants should remain undisturbed and no light should be turned on, because the ongoing processes will be dis-turbed and plant growth will be somewhat slowed. Also, some species need a minimum time of continuous darkness to fl ower.

by Réal Adam,P.E and Isabella Lemay, agr


Controlling Climate Conditions


Keep the Stomas OpenPlants are also living organisms with

failsafe mechanisms encoded in their DNA to survive the ever-changing climate conditions in a natural out-door environment. They act like each species has its own personality. They are sort of moody when it comes to climate conditions. The plant breathes through stomas mainly located at the lower surface of leaves. These stomas act like two-way valves to let air in and expel unwanted gases and water vapor from transpiration. When one climate condition is threatening to damage part of or the whole plant the stomas close. Even if light, water, and nutrients are available in abundant quantity and quality, when the stomas shut the photosynthesis stops, hence the growth and the blooming. The plant maturation stops until the climate variable that caused the stomas to close gets back in the appropriate range for the plant to operate photosynthesis and growth. So, climate conditions are important to plants and climate control

in a closed environment is a must. If temperatures are too hot or too cold, or if the relative humidity is too low, growth stops. When

relative humidity is too high transpiration is slowed, so water and nutrient absorption slows accordingly. Relative humidity going too high is also a concern because of the risk of pests like fungi and bacteria, which will a�ack plants if allowed to develop.

How Important is CO2?Basically, when stomas close the carbon intake from breathing

the carbon dioxide shuts down and the plant is deprived from this important source of building material for the cells. Plants are made up of organic chains composed of oxygen, hydrogen, nitro-gen, and carbon. If any of these atoms are unavailable in the right

Diagram of a plant stoma

Photograph of an open stomawith a magnification of 2900X.

The number of stomas varies with the plant speciesfrom 30,000 to 325,000 per square inch.

>CONTROLLING CLIMATE CONDITIONS



proportion, tissue building and growth are slowed to use just what’s available. Since hydrogen, oxygen, and nitrogen may come from water pumped through the roots, car-bon dioxide from the air becomes central to further fast growth. Proper temperature and relative humidity will keep the sto-mas open for carbon dioxide intake in the presence of light. Thus, it is important to maintain minimum ventilation with fresh air to supply the plants in carbon dioxide as it is drawn and used. Climate control is obviously important to maintaining proper conditions for growing plants at a sustained high rate in a closed room.When plants appeared on Earth and

evolved into the various species, carbon dioxide levels were much higher than they are now. These concentrations of CO2 were certainly above the 1000 parts per million (ppm) compared to the 400 ppm average that can be measured outdoors in a highly urbanized area. So many species of plants will react, grow, and mature faster at higher levels of carbon dioxide. That’s why carbon dioxide enrichment is extensively used by

growers, providing more building material for the plant to transform into biomass and to get faster and higher yield results.

Controlling Climate isDemanding

So, plants are somewhat bad-tempered. Each species requires a specific set of cli-mate conditions, which are different at day or night. Yet if the grower wants to get the best possible results, he has to make sure the conditions are maintained within a range close to the actual required se�ings. A grower can choose to manage the condi-tions himself by watching meters, push-ing bu�ons, and turning knobs to raise temperature and lower relative humidity, as for day and night. He may also choose to use simple controls: a lighting timer is fine; a cycle timer for repetitive operations like irrigation is also fine. When it comes to temperature and humidity controls, a sim-

An orchids enthusiast indoor grow room

When plants appeared on Earth and evolved into the various species, carbon dioxide levels were

much higher than they are now

“For Relative humidity, a range as low as five percent

might be required.”



ple thermostat and hygrostat will not fit unless they are expensive controlling devices that can maintain a condition in a very close range and are set to operate at different day and night se�ings. To control temperature, a range as tight as ± 2 degrees Fahrenheit (± 1 Celsius) around the se�ing is needed. For relative humidity, a range as low as five percent might be required.Climate controllers with digital sensors and day or night rec-

ognition offer these tight ranges and high accuracy. Again, one may choose to enrich the atmosphere of the grow room in carbon

dioxide under the control of a timing device. What is the actual CO2 concentration in the room? Is it in the right range for the plant to maximize its use of CO2 and grow faster? A CO2 controller is easy to set, offers the grower a displayed value of the actual concentration, and sometimes records hourly average readings to monitor the good working condition of the enrichment system. Climate controllers certainly cost more, but will certainly bring results according to the species and the grower’s se�ings.

Single Variable Controller or Integrated?Temperature modifies relative humidity. Carbon dioxide enrich-

ment by burning propane or natural gas produces heat and water vapors, increasing temperature and relative humidity accordingly. Then growers want to lower the temperature, o�en using fans to bring cool air in the growing volume and evacuate outside warm air, thus expelling the CO2-enriched air at a cost. Other growers just want to regularly draw fresh air to use ambient CO2. Many of them use air conditioning units to lower temperature and relative humidity by condensing water vapors, while some would rather use dehumidifiers. No grow rooms are the same; no two growers manage their grow room and crops the same way. Maintaining a growing environment climate at optimal cropping conditions can be pre�y tricky. Again, ensuring a 24/7 full control is time con-suming and requires a constant human presence. The grower al-


Tomato plants thriving in an indoor garden

“Temperature modifies relative humidity.”



ways has to think about cause and effect. For example, lowering the temperature by venting air out of the grow room during the CO2 enrichment process is just like throwing money out the window. Lower-ing temperature with an air conditioning unit may dry the air to the point where the plants are comfortable according to the

thermometer, but relative humidity is too low and the stomas will close. So, climate variables are totally linked.Beginners and inexperienced growers

generally start with individual climate parameter controllers. A temperature con-troller is used for heating, a temperature controller adjusts for cooling, a specific

controller for CO2 enrichment activates a generator or a bo�led gas regulator, and so on and so forth. Some of these proc-esses are controlled by timers. Individual climate parameter controllers all have to be set and watched very closely because se�ings can easily generate opposite proc-esses operating at the same time. Also, even if individual climate parameter controllers and timers are cheaper than integrated controllers overlooking two or more cli-mate parameters, they fill your grow room with wires and apparatus and get hard to understand and manage. In fact, integrated controllers measure,

analyze and activate at least two proc-esses involving climate parameters. These controllers, with digital measurements and analysis, are programmed with computing routines to optimize the processes they


DISTRIBUTION TUBINGT-FITTING

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ADJUSTING SCREW

REGULATOR

SOLENOID VALVE

FLOW METER

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A bo�led carbon dioxide enrichment apparatus

“Integrated controllers are more expensive but are the first choise of experienced

and knowledgeable growers,...”


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control, in accordance with the grower’s se� ings. Integrated controllers are more expensive, but are the fi rst choice of expe-rienced and knowledgeable growers, who regularly check and record the climate con-ditions evolution every day of their crop growth, from seeding to harvesting. These growers measure their harvest weighing, counting and computing yield per square foot and per dollar invested.

Overall, It’s a Matter of Results and the Cost Incurred to Obtain These Results.

Growing plants in a closed controlled en-vironment with the objective of crop yield is quite challenging. To maximize results, every eff ort has to be made to keep the plant stomas opened at all times, facilitat-ing air exchange and carbon dioxide intake, as carbon is a major building material of the plant cells. Plants have a unique temper for each species and the grower in a closed environment has to control all climate pa-rameters very closely in order to obtain the desired results without inducing adverse eff ects. One climate parameter going out

of sight and the plant will not benefi t from the appropriate light, nutrients, and water brought by the grower. In this instance photosynthesis is slowed or stopped or, worse, toxins are generated in the plant and are not evacuated.Climate control is truly demanding. On

the one hand, single climate parameter controllers are cheap. However, to off er some accuracy to satisfy plants’ needs they must be manually set, and the controlled processes of heating, cooling, ventilating, and others have to be constantly watched in order to avoid opposite processes operating at the same time. On the other hand, integrated controllers overlooking at least two processes can be the best choice for experienced growers. They are more expensive but are built with automatic intelligence and sound management of the processes they control. Any grower has to decide on the results he expects and choose the climate controller(s) that will enable him to realize his goals. In the end, it’s all a ma� er of results and the cost incurred to obtain these results.


A propane gas carbon dioxide generator for economical enrichment.



YOUR TOMATO PLANTS LOOK LIMP AND SICKLY. Their lower leaves have turned a nasty yellow between the veins. You need to do something quickly. Searching the web, you discover your to-matoes have magnesium defi ciency. Under the bathroom sink you fi nd an old bag of Epsom salts and an empty spray bo� le. Dissolving a tablespoon of the salts in a couple of pints of warm water, you spray the leaves of the tomato plants all over. A couple of days later the plants are bright green and healthy again.From this example it looks like foliar

spraying could be the magic bullet we are all looking for. Within one hour, according to scientists, a plant can transport minerals from its leaves all the way down to its roots. Compared to root feeding, this looks like

the fast track. However, foliar spraying is not an alternative to good growing meth-ods. It is best seen as a powerful addition that has its own secrets for success.

MINERAL DEFICIENCY SPRAYING Spraying for mineral defi ciencies can be par-

ticularly eff ective: magnesium for tomatoes, zinc for grapes, boron for many vegetables; the list is long and complex. Plants signal their need for help by exhibiting distress in leaf, bud, and fl ower. As the plant’s “primary care person” your task is to diagnose the problem and provide corrective procedures. Mineral spraying acts rather like an injection; it gets the medicine into the plant’s system as quickly and effi ciently as possible. The main stumbling block is our limited

diagnostic skills. Each species of plant has

both general and specifi c mineral needs. When these minerals are missing from the soil or hydroponic solution a range of confusing symptoms appear. We may not discover the specifi c reason quickly enough to prevent plant collapse. Even when we do, that plant will take time to recover and might never reach optimum productivity. Spraying for mineral defi ciencies is emer-

gency medicine — fast and effi cient. To be successful we need to know which element is missing and have the cure ready to hand. This is not always possible, so, in general, it is be� er to think in terms of prevention rather than cure. We do not wait until we’re sick to take vitamins (a contraction of “vital minerals”). So, rather than spraying when a defi ciency appears, put in place a


program of foliar fertilization to increase plant health and resilience. If deficiency spraying is specific first aid, foliar fertiliza-tion is preventive health care.

FOLIAR FERTILIZATIONWe all have had the basic course in fer-

tilization: plants need NPK — nitrogen, phosphorous, and potassium. This is like saying humans need carbohydrates, fats, and protein. It tells us the basics but certainly does not say how to eat well. We need a balanced diet with nourishing foods, and plants are similar. They prefer nutrients in which the complex chemicals are bound organically. Rather than a dose of chemical nitrates, plants thrive best on organic products that provide not only the NPK but also a range of trace elements.

by Roland Evans

Vegetation evolved in the oceans, bathed in a solution containing every imaginable mineral. Seaweed takes food directly from seawater. Land plants, like their marine ancestors, can take in nourishment through the pores or stomata on their leaf surfaces. Stomata are tiny mouths that breathe in CO2 and exhale water and oxygen. They also transport nutrients up to ten times more efficiently than root systems. Foliar feeding bolsters the nutrients available to each plant, like a regular dose of vitamins and supplements.Most vegetation requires a minimum of

16, but probably more like 50, essential

minerals and trace elements. Is it just coin-cidence that some of the best providers of these elements come from the ocean? Fish products are high in organic nitrogen; kelp is a wonderful source of minerals, particu-larly potassium, and algae have a range of trace elements and hormones beneficial for cellular development. Research suggests that natural sea salt contains a vast range of trace elements. When sprayed in a very diluted form, sea minerals provide most elements needed to prevent deficiencies.Foliar fertilization is fast becoming an

essential addition to standard cultivation techniques. For many growers who have


grown up with chemicals it is a small step to organic fertilization; the NPK is just packaged diff erently. However, there is another, less well-known aspect to plant cultivation based on biology rather than chemistry — the realm of the microbes.

SPRAYING WITH COMPOST TEAWhen plants evolved on land they formed

an alliance with the microbial life in the soil and air. Certain species of bacteria and fungi became the chefs that prepared the plant’s food, the medics that helped them fi ght disease. Plants like to dine on biologi-cally predigested nutrients; it is easier for them to assimilate. Healthy plants have a strong immune system that includes a “bio-fi lm” of microbial life on the roots, stems, and leaves. To make use of these biological principles to feed and protect our plants, we can spray with compost tea.Compost tea is “brewed” by aerating a

mixture of water, compost (sometimes hu-mus or worm castings), and organic nutri-ents such as molasses, kelp, fi sh emulsion, and yucca. This produces a nutrient-rich solution containing vast colonies of benefi -cial bacteria and fungi. The microbes digest

the nutrients into organic compounds that can be easily taken in by the plant. These same microbes colonize the surface of the leaves to help fi ght off disease.When you spray with compost tea you

envelop the plant with living organisms and you enhance the web of life of which the plant is a part. The results can be astounding: large, mineral-rich vegeta-tion with clear glossy leaves, decreased disease, and even reduced insect a� acks. Plants treated with foliar fertilization, and especially compost tea, has higher “Brix” levels — a measure of the carbohydrates and mineral density in the sap. High Brix is said to make the plants less a� ractive to pests and more resilient to stress. If they are vegetables, they even taste be� er!Compost tea, unlike mineral sprays and

foliar fertilization, cannot be over-applied and does not burn leaves. The microbe-rich droplets drip off the leaves to improve soil and growing solutions. Those same microbes can clean up toxic chemicals and turn them into nutrients. The main drawback is that brewed compost tea is not always available and, being alive, has a limited shelf life. If you brew your own

>THE SECRETS OF FOLIAR SPRAY



compost tea, it needs to have the best in-gredients and proven test results.Whether you apply a mineral solution

to defi cient plants, have a regular foliar fertilization program, or go the distance with compost tea, foliar spraying benefi ts your plant quickly and profoundly. Find that old spray bo� le, hook up your hose-end sprayer, and invest in a commercial spray pack. Once you see the results, you will never neglect this method of plant care again.

TIPS ON SPRAYINGHere are guidelines for foliar spraying:• When mixing up your formulation, wheth-

er mineral, organic fertilization, or compost tea, use non-chlorinated, well-oxygenated water. Bubble air through chlorinated wa-ter or leave it to off -gas overnight. You can try using seltzer in your foliar spray to give plants an added CO2 boost.

• Make sure mineral ingredients are dis-solved and the solution is very dilute. Chemicals in high concentration tend to “burn” foliage and leave a salt resi-

due. Compost teas need to be diluted 10 to 1.

• Add a natural surfactant or we� ing agent to help the solution fl ow over and stick to foliage. Yucca is a natural surfactant and is o� en a component of compost teas. Use true organic soaps such as Dr. Bronner’s, Tom’s, or Pangea. The great majority of other soaps contain deter-gents that do not break down easily.

• Young transplants prefer a more alkaline solution (pH 7.0) while older growth prefers a somewhat more acid spray (pH 6.2). Use baking soda to the raise pH of your spray and apple cider vinegar to lower it.

• Spray with a fi ne sprayer for foliar ferti-lization and with a coarser, low-pressure sprayer for compost tea. The microbes in compost tea need large protective water droplets. Apply in the early morning or evening when the stomata are open. Do not spray if the temperature is over 80ºF (~27ºC) or in the bright sun. Harsh ultraviolet rays can kill microbes in compost tea.

• Cover at least 70 percent of the foliage, paying particular a� ention to the under-surfaces of the leaves.

• Apply foliar fertilization or sprayed com-post tea every two to three weeks during the growing season.

>THE SECRETS OF FOLIAR SPRAY




When thinking of gra� one immediately thinks of people taking bribes for services rendered, but gra� s have had and continue to have an important role to play in horticulture. For example gra� ing (and it’s subset budding) has been an important technique to control plant vigour for fruit trees for many years. It provides a means to establish specifi c varieties (clones) of the majority of fruit trees (such as cherries and apricots etc.), which do not breed, true from seed and cannot easily form roots from cu� ings. The development of dwarfi ng rootstocks in apples has had a major impact in the way in which apples are produced, compared with say 50 or 100 years ago.

by Mike Nichols

GRAFTINGMassey University, New Zealand


Gra�ing also has a role to play in vegetable production, particu-larly (but not solely) in controlled environment agriculture. It is not a new technology, in fact information on the benefits of using gra�ed vegetables seedlings was first published in the 1920s, but like most new technologies it was not taken up immediately, and it was not until the 1960s that it started to become popular.The major vegetable crops being gra�ed are: tomato, cucumber,

eggplant, melon, pepper and watermelon. The main purpose of the gra�ing is to provide pest and disease tolerance, but toler-ance to low soil temperatures, and high salts can be additional advantages.In the 1960’s it also became a method to provide resistance to soil

borne pathogens such as Fusarium, Verticillium and Nematodes for a range of vegetable crops, including tomatoes, cucumbers and melons.It has become a particularly popular practise in Asian countries,

where the small farm size reduces the opportunity for long rota-tions and therefore increase the potential for pest and disease build up in the soil. The introduction of protective cropping in these countries using plastic film clad houses, resulted in plants being more stressed, and being cropped for a longer period than in the field. Gra�ed seedlings were useful in overcoming some of these stresses.

Information in 2000 from Japan and Korea (see Table 1 a�er Lee (2000)) demonstrates the relative importance of gra�ing for a range of vegetables though strangely very few tomatoes were gra�ed in Korea and yet this is one of the more popular gra�ed plants in Europe.


My first practical involvement with the grafting of vegetable seedlings was at Massey University in the mid-60’s, when we had some problems with Fusarium in greenhouse cucumbers. Using fumigants to “sterilize” the soil prior to planting was not proving successful, so we decided to gra� the cucumbers onto the rootstock of the Malabar gourd (Cucurbita ficifolia). The method worked well, so the following year we used the method again, only this time using a new variety of long (telegraph) type of cucumber, the recently developed

only female flowering (gynoecious) vari-ety “Princess”, which by producing only female flowers did not therefore require either the removal of male flowers or the restricting of pollinating insects. (Note: Tel-egraph cucumbers developed a bulge at the end of the fruit if they are pollinated!)It was an interesting experience, because

at that time cucumber gra�ing involved beheading the rootstock, cu�ing the roots off the scion-making a V-shaped cut in the rootstock and inserting the scion into the v. As the C. ficifolia stem is hollow it looks

easy just to stick the scion into the centre of the rootstock, but in fact no true gra� occurs as the scion develops adventitious roots, which grow down the stem into the soil--without any gra� effect. It is essential that the scion be inserted into the solid stem of the rootstock, so that a true gra� occurs, a trap from inexperienced “growers”. The operation normally requires mist propaga-tion facilities because there is a major check to the growth of the scion.The check was quite clear with our gra�ed

“Princess” cucumbers, as the plants revert-

>GRAFTING

Crop

CucumberEggplantMelonPepperTomatoWatermelon

10,160

Total (ha)

Field + Tunnel Greenhouse

JAPAN KOREA

GreenhouseField + Tunnel

% grafted Total (ha) % grafted Total (ha) % grafted Total (ha) % grafted

55 5,540 96 1,728 42 5,964 9511,816 43 1,785 94 650 0 413 26,142 0 8,258 42 1,047 83 9,365 952,684 1,468 75,574 0 5,085 56,459 8 7,141 48 258 0 4,752 5

14,017 92 3,683 98 13,200 90 21,299 98

Table 1: Area of vegetables (and % gra�ed plants) in Japan and Korea in 2000. (a�er Lee, 2003)


ed to producing only male fl owers on the main stem, which made for an interesting lesson. These days the female only characteristic in greenhouse cucumbers is much stronger, so the experience is unlikely to occur.At about this time the gra� ing of tomatoes became popular in

some parts of the world. There were a range of rootstocks available, which incorporated resistance to Fusarium, Verticillium, corky root and Nematodes the so called KVNF root stocks. The so-called “su-pertom” so successfully promoted by Alan Naish from Kakanui in New Zealand was a gra� ed plant. Gra� ing at this time was a tedious business, as it involved growing both the scion and rootstock, and then making a small V shaped cut in both stems, and then sliding the cut pieces together (inarching). Once the plants are properly callused and joined, the top of the rootstock and the roots of the scion variety can be removed. Planting must always (of course) be undertaking with the scion well above soil level, so that no scion rooting can occur.My fi rst experience of gra� ing tomatoes was in the late 60s, when

I decided to show the technique to a group of students from the Cook Islands.My demonstration was (to put it mildly) a li� le ham-fi sted, as I had

never gra� ed tomatoes before. It was therefore very traumatic for me when the students demonstrated to me how they did the tomato gra� ing in the Cook Islands. It was a standard technique that they had learnt on their “mother’s knee” to overcome bacterial wilt!!Following the interest in the 60’s, gra� ing became of less impor-

tance, probably because of the growing interest in hydroponics, and the thought that it was a totally “sterile” system, and it was not until the 90’s that industry again became interested in this technology again.In the Netherlands and Japan one of the main uses of gra� ed root-

stocks is for eggplant (aubergine). Gra� ing onto a resistant rootstock not only provides greater vigour, but also off ers resistance to both virus and root diseases.

“ In the Netherlands and Japan one of the main uses of grafted

rootstocks is for eggplant


Interestingly, a paper recently presented by Mr Palada from AVRDC at the recent Singapore hydroponics symposium (Practical Hydroponics 85, p 40) showed how gra�ing tomatoes onto eggplant increased tomato tolerance to flooding and to bacterial wilt diseases in Taiwan, Philippines and Vietnam!Perhaps all things are relative, and the enhanced productivity

obtained by gra�ing onto eggplant in these tropical areas would be considered an unacceptably low productivity in an intensive temperate greenhouse situation.Since the 60’s the technology had changed, and the need to retain

the roots on the scion a�er gra�ing is now considered unnecessary, and gra�ing now involves slicing the root stock and the scion at a 45 degree angle, and holding them together by means of a plastic clip. The gra�ed seedlings are then placed in a high humidity (mist propagation chamber) for five to seven days, to keep in the scion turgid, while the gra� takes, before being slowly weaned back into normal conditions.Of course gra�ing costs money. Not only is it necessary to grow

two sets of plants, but there is also the labour required to undertake the gra�ing, and the mist propagation facilities. So why gra�? I guess there are two main reasons; the first is that no ma�er how sterile the medium in which the crop is to be grown, over time path-ogens will inevitably be introduced. By using a resistant rootstock the reduction in productivity is minimised, so that the crop and can be grown for a longer time before it is necessary to replace it. Every time a tomato crop of (for an example) is removed there is about an eight-week turnaround before harvest commences again.Because gra�ed plants tend to have greater vigour (however, see

my later comments) it is possible to grow at least two stems on every plant, and thus the cost of propagating each plant is greatly reduced.However as one might anticipate there is a delay from sowing the seed to first harvest, due to the check involved in gra�ing. How-ever because this occurs during the propagation stage it is of li�le importance in the cropping house.

>GRAFTING


HOW TO GRAFT -Obviously it is necessary to sow two sets of seed, namely the

rootstock and the scion variety. Experience has suggested that the rootstock should be sown several days before the scion variety, as not only is germination a li�le more erratic, but also the seed takes a li�le longer to germinate. The ideal size for gra�ing is when the stems of both the scion and rootstock are 1.5 mm in diameter. Almost certainly this will mean some need for grading the rootstock seedlings a�er emergence, to ensure that all the rootstocks in a tray are the same diameter.Growing the seedlings in plug trays makes it possible to grade,

but this must be done at least 2 days prior to gra�ing, to give the plants time to get over the check.If the rootstock is germinated at 25C it takes about 17 days to

reach the 1.5 mm diameter.The growth of the scion variety can be controlled with tempera-

ture, to ensure that that the scion and rootstock are at the correct size at the same time.It is essential that the gra�ing area is hygienic, and all equip-

ment clean. Knives should be disinfected regularly to avoid the possible spread of virus.When gra�ing the first stage is to remove the heads of the root-

stock and throw away the heads to ensure that they do not get mixed up with the scion variety.The cut is made at a 45° angle at a hight of 2-2.5 cm above the

pot. Too low and there is the risk of scion rooting, and too high, and the gra� may become too heavy and fall over.


The gra� ing clips are then a� ached to the rootstock.The scion variety is prepared by cu� ing the seedlings plants

head to a length of 1-1.5 cm. Again a 45° angle cut is made. This provides the maximum possible surface area for the rootstock and scion to fuse. The scion is then inserted into the gra� ing clip, until the rootstock and scion cut surfaces make full contact.The gra� ed seedlings must remain in the high humidity envi-

ronment (mist propagation) for at least 4 days, to ensure that the scion remains turgid, and the gra� takes; then over several days

the humidity should be slowly reduced to glasshouse levels. Normally full ventilation should be possible a� er day 7.It is not necessary to remove the gra� ing clips, they fall of natu-

rally, in fact removing them by hand may damage the plants.Currently the most common rootstock used for gra� ing tomatoes

is “Beaufort”, from the Dutch seed company De Ruiter (which is resistant to Corky Root, Fusarium, Verticillium, Nematodes, and TMV but this is being rapidly being replaced by Maxifort (also from De Ruiter). Other rootstocks are Eldorado from Enza, and 61-063 from Rĳ k Zwaan.Rootstocks vary in their vegetative/generative characteristics,

and it is really a question of selecting the appropriate rootstock for your scion/ production system/ planting date.Where vigour is desirable, then a highly vegetative rootstock

should be selected, but growing a crop into the winter a genera-tive rootstock might be favoured. One of the advantages of a vegetative rootstock is that it intro-

duces the opportunity to grow two (or more) main stems to a single root system, with a consequential reduction in propagation costs. This might almost negate the additional cost of producing gra� ed seedlings. The bonus, then, would be a potentially more productive plant which would resist soil borne pathogens, and grow be� er during cool conditions.

>GRAFTING

“... grafting has the potential to markedly increase productivity.”


Of course there are pros and cons for any technology, and this must be carefully weighed up by the individual grower in his/her specific situation.Certainly in general there are many advantages of gra�ing,

not the least being the improved productivity due to resistance to disease. It also appears that gra�ed plants (via the rootstock) are more tolerant to poor water quality (salinity) an increasing problem in some countries. Tolerance to low temperature is also another potentially important characteristic. Tomatoes gra�ed onto the rootstock KNVF grew well at low soil temperatures (10-13 C) in contrast to the non-gra�ed plants. In the same way gra�ed water melon performed be�er than ungra�ed at low temperature, and gra�ed eggplant similarly. Of course it is essential to have the appropriate rootstock, as some rootstocks are not suitable. (see Edelstein, 2004). He found that there was a marked differ-ence in productivity when growing cucumbers ungra�ed and on 4 different roots stocks. As one might anticipate the ungra�ed plants were a li�le more precocious in cropping, as they had not gone through the gra�ing check, but this advantage was soon eliminated, and the gra�ed plants were the most productive. In fact by the end of the experiment the ungra�ed plants had only


produced 26 kg/m2, and the best treatment (gra�ed onto the rootstock Shintoza) nearly 35 kg/m2. The plants gra�ed onto the other 3 rootstocks produced 30kg/m2.The take home lesson from this is that gra�ing has the potential

to markedly increase productivity, but there is a probably a need to match the rootstock to the scion for best results.In terms of productivity, it appears that gra�ing will not only

increase yield (for melons there is a reported increase of 50-60%), but also the more vigorous root systems may also increase water efficiency and nutrient absorption.

Of course nothing in this world is perfect, and there can be dis-advantages to gra�ing.The first one to consider is cost. Clearly it is going to be more ex-

pensive to produce a gra�ed seedling than an ungra�ed seedling. There is also a question of having the technical skills available to undertake the gra�ing.Incompatibility is another potential problem. This is failure of the

scion to unite properly with the rootstock, causing poor growth or premature death of the plant. This has been noted on occasion with Cucurbita ficifolia and melon, and also when tomato is gra�ed onto Datura tatula. However this should not really be a problem provided that care is taken to use rootstocks and scions with a good prehistory of success. There have also been some examples of gra�ing causing fruit shape and taste differences, but in general the benefits of using gra�ed plants far outweigh any risks.

References.Echebarria P H (2001) “Influence of different rootstocks on the yield and quality of greenhouse grown cucumbers”.Acta Hort. 559, 139-143. Edelstein M (2004) “Gra�ing vegetables-crop plants:Pros and cons.” Acta Hort. 659, 235-238.Lee J M (2003) “Advances in Vegetable Gra�ing”Chronica Horticulturae, 43 (2), 13-19.

>GRAFTING


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A BRIEF HISTORY OF REVERSE OSMOSISThe process of osmosis was first described

by a French scientist in 1748. More than 250 years later a modification of this process known as reverse osmosis has become the best and most efficient method to purify undesirable water into virtually pure H2O. Reverse osmosis, as we know it today, was developed in the late 1950s and has changed li�le since then. Reverse osmosis machines have go�en more advanced, as has membrane technology, but the essen-tial principles remain the same. It is used for producing a few gallons of drinking water a day for residences to millions of gallons per day for industrial processes, and even for desalinating seawater.

by Richard Gellert

REVERSEOSMOSIS:

Take the Plunge


Normal Osmosis

Direction of Water Flow

Higher ContaminantConcentration

Lower ContaminantConcentration

SemipermeableMembrane

Reverse Osmosis

Direction of Water Flow

Membrane

Pressure

WHAT IS REVERSE OSMOSIS?In order to describe reverse osmosis, it’s

best to explain the phenomenon of osmosis. Osmosis involves the selective movement of water from one side of a membrane to the other. According to Merriam-Web-ster’s Collegiate Dictionary, osmosis is the “movement of a solvent through a semi-permeable membrane into a solution of higher solute concentration that tends to equalize the concentrations of solute on the

two sides of the membrane.” Now, that’s a brainteaser.For the purposes of this article, reverse

osmosis (RO) is essentially a water treat-ment process that removes undesirable materials from water by using pressure to force water molecules through a semi-permeable membrane.This process is called “reverse” osmosis

because the pressure forces the water to flow in the reverse direction (from the

concentrated solution to the dilute solu-tion) to the direction of flow in the process of natural osmosis (from the dilute to the concentrated). Pressure forces contami-nated water through the membrane. Since contaminants cannot cross the membrane, purer water collects on the other side and can then be used or stored. The contami-nants are stopped at the membrane and continue down the wastewater stream.The RO membrane consists of several


thin layers or sheets of film that are bonded together and rolled in a spiral configuration around a plastic tube. The material of the membrane is semi-permeable — it allows water molecules to pass through while acting as a barrier to dissolved solids. Most RO systems have two pre-filters — a sediment and a carbon — to pre-treat the water before it is passed through the RO membrane(s).

HEALTH BENEFITS FOR HUMANSWhether or not RO water is good for your body is a hotly de-

bated topic. Research the subject and you will find two completely separate schools of thought. One theory argues that in order for a mineral to be of any use to the body it must be presented in a form that is readily absorbed. That form involves an association with an organic (carbon-based) molecule. Carbon-based molecules are to be found in living systems, and are not found in the ground, which is where mineral water comes from. The minerals that come from ground water are in salt form. When salt is presented to the body (with rare exceptions such as sodium chloride, i.e., table salt) it must be either stored or excreted. These unusable minerals accumulate and cause all kinds of health problems, such as cataracts, kidney stones, and arteriosclerosis. This theory also says that purified water, RO or distilled, leeches

the body of minerals in the unusable, ionic form, which is a good thing. We want these to leave the body rather than be deposited and cause disease. From where, then, should we be ge�ing our minerals? Plants, of course! Plants and vegetables have read-ily available forms of minerals because they are biologically bound.The arguments against drinking demineralized water are that

we lose a primary source of necessary minerals in our diet. More so, water that has lost its own minerals will a�ract and absorb

Some Potential Drinking WaterContaminants and Their Typical Ranges

of Rejection with an RO System

Contaminant

SodiumCalciumMagnesiumIronCadmiumLeadNitrateOrganic HalidesTrihalomethanesChlorineTotal Dissoved Solids

87-93%80-97%80-98%90-98%96-98%96-98%50-92%83-92%65-99%13-91%95-99%

Range

>REVERSE OSMOSIS: Take The Plunge


minerals in our body, causing a mineral deficiency. The theory states that, in fact, the minerals in water are readily absorbable and constitute a percentage of the healthy mineral content in our bodies. Proponents of mineral water say the calcium and magnesium

it contains are essential elements for our body. They can be provided to us in food, but even diets rich in calcium and mag-nesium may not be able to fully compensate for their absence in drinking water. Nutritional studies suggest that some other micronutrients may also have a beneficial role associated with their presence in drinking water.There are endless books wri�en and studies done that encour-

age both theories. I suggest further researching the topics to become fully enlightened and to make the proper decision for your drinking water. One thing is for sure — drinking straight tap water is risky these days, and buying countless bo�les of mineral water is environmentally irresponsible.

PLANTS AND REVERSE OSMOSIS WATERThere are many benefits of using reverse osmosis water for your

prized plants. In order to have a successful crop and explosive yields you must start with a clean base for your water. Close to 0 ppm in your water allows you to dial in the perfect feed program and realize the biggest flowers and tastiest fruits you can imagine. People that use RO water for their plants can never go back to tap water a�er seeing the enormous difference it makes on their harvests.

IN AND OUTS OF RO SYSTEMSSo, if you already own an RO system or are thinking about acquiring

one, you need to know how to get the most out of it. There are four basic factors that determine the flow of water from an RO system: inlet pressure, temperature, PPM and the gallons-per-day (GPD) rating of the membrane.


The higher the inlet pressure the faster the flow. Most households on municipal water sources have between 40 and 80 pounds per square inch (psi) in their pipes. Typical residential or hydropon-ics-oriented RO filters require at least 40 psi and no more than 80 psi of pressure. People on well or spring water generally have a pressurizing system to create pressure in their pipes. These are adjustable and commonly set at 50 psi. If, however, neither of these situations is providing adequate pressure, a special RO booster pump may be required to increase the pressure to the RO system and obtain the proper flow needed.The higher the inlet temperature the faster the flow. In areas

where the winters are cold an RO system may slow down. Not much can be done about inlet temperature and it is not as big of a concern as the other factors that determine flow. Most RO mem-branes are rated at 77ºF (25ºC), so unless you live in a very warm area, you can expect slightly slower flow than the rated values.The higher the ppm of the inlet water, the slower the flow. This

is only reasonable because the more contaminated the inlet water the harder the RO system has to work to get rid of contaminants. Reverse osmosis systems typically reject 90 to 98 percent of all ppm of total dissolved solids. If the ppm is very high due to excess

hardness (calcium, magnesium, or iron) then a water so�ener is a good idea as a pre-filter for the inlet water.The GPD rating of the membrane or membranes is a very im-

portant factor in determining flow from an RO system. Typical residential drinking water systems use a 30 GPD membrane. Since the water flows so slowly from these systems, it is accumulated in a three to four gallon pressure tank. When the faucet is opened to draw water, it comes from the tank and not directly from the RO system itself.Reverse osmosis systems designed for hydroponic use typically

have one or two 100-GPD membranes. There are even some high-flow systems that have two 375-GPD membranes, giving a total flow of up to 750 GPD per day. These systems are designed for direct flow into an atmospheric (non-pressurized) storage tank or reservoir. People generally use a float valve system to fill the tank una�ended and ensure it does not overflow.Reverse osmosis is the best method for treating large amounts of

water for your plants. The systems are affordable and can produce a gallon of pure H2O for pennies. You will notice a huge difference in yield and quality of your harvests. Many hydroponics shops carry a variety of filters and can help you decide which one is right for you and your garden.

>REVERSE OSMOSIS: Take The Plunge

Typical % of Contaminants Removed by Reverse OsmosisMaterial/Element % Removed Material/Element % Removed

Arsenic +3Barium

CadmiumChlorideCopperFluoride

InsecticidesMagnesium

NitratesPotassiumSelenium

SilverStrontium

70%97%97%92%97%98%97%97%80%92%97%85%97%

Arsenic +5Bicarbonate

CalciumChromateDetergentsHerbicides

LeadNickelPCB’s

RadiumSilicateSodiumSulfate

Total Dissol. Solids

98%94%97%97%97%97%97%97%97%97%96%92%97%90%

* Feed water: 60 psi, 76 degrees Fahrenheit, pH of 8



by Erik BiksaThe production of fresh strawberries provides an excellent opportunity

for home and market gardeners to enjoy a be� er-quality fruit and perhaps generate a li� le side income. Large-scale outdoor hydroponic cultivation could replace traditional strawberry growing methods in some of North America’s largest producing areas. This is largely due to environmental and health concerns raised and lobbied concerning commercial fumigants, on which conventional fi eld-berry growers rely heavily for disease, weed, and nematode control.In other areas of the world, and in some progressive North American opera-

tions, large-scale hydroponic strawberry production has been practiced in earnest for some time now. Because the plants are no longer grown in soil, commercial soil fumigants are no longer required, signifi cantly reducing any potential harm to the consumer or the environment.


So, what is the significance to the home or market gardener? Strawberries do not store or transport well. Some commercial varieties are bred for be�er post-harvest handling characteristics, but this can com-promise taste — namely sweetness in the strawberries. This provides an excellent opportunity for small-scale commercial strawberry production to support local demands. It is advisable to target produc-tion and harvesting periods when local prices are at their peak, typically during the winter and early spring months. In most regions a greenhouse or cultivation indoors under lights is necessary during these peak periods due to outdoor climatic limitations. Currently, the media are dis-cussing the “100-mile diet” wherein the consumer makes a conscientious effort to purchase food that is produced within a hundred-mile radius.As with any growing endeavor, variety

and selection is the key. Strawberry varie-ties best suited for greenhouse cultivation are classified as being short day or day neutral. Basically, these plants will flower

and produce fruit with shorter photope-riods. Sweet Charlie and Camarosa are popular short-day varieties while Selva and Seascape are commercial day-neutral producers. These are proven varieties. Temperatures also play a role in triggering a strong flowering and fruiting response in strawberry varieties. Indoor growers gardening under lights have the luxury of choosing whatever variety best suits their operational budgets or personal tastes because photoperiods can be maintained as long or as short as required to produce fruit. For example, growers using HID lighting can produce long-day varieties, which would be impossible for commercial field growers during seasons with shorter light durations.Market gardeners also have the important

option of producing their crops organi-cally, which is o�en more feasible for the

smaller-scale commercial producer. If properly marketed, organically grown berries can fetch a considerable premium over conventionally produced varieties, and can enjoy a stronger demand amongst select clientele.In either case there are a variety of

methods by which the home or market gardener can produce their crops. Hydro-ponic systems such as NFT or perlite-filled bags are favored among berry growers. Strawberry roots don’t do well with water pooled around them. In an active recircu-lating system such as NFT, good aeration of the nutrient solution and ensuring that the channels drain well is important. Maintaining reservoir temperatures below 70°F (~21ºC) will also promote a healthier root system less susceptible to infections of Pythium, which can spread quickly in a system where warm, stagnant conditions prevail.It is advisable to inoculate the root systems

of young plants with beneficial bacteria and fungi, such as species of Trichoderma and Bacillus. An additional source of carbo-

“Perlite appears to be the medium of choice for greenhouse and indoor

strawberry producers.”


hydrates will help young plants thrive as well as nourish and assist the beneficial microorganisms that have been introduced. From time to time, growers might choose to reintroduce the microorganisms to the growing system to help ensure that higher populations of aerobic organisms outnum-ber anaerobic (bad) microorganisms.Occasional applications of products with

enzymes that are intended to promote healthy root systems are also recom-mended. These enzymes will help hasten

the biological breakdown of old or decaying roots. Not only

does this help to further eliminate the possibil-

ity of contracting a root disease, but the end products of the breakdown of old or decaying

root matter supply many substances that are beneficial and that can be taken up by the crop. The enzymes also perform a sort of “bio-chemical peel” to the roots; they will strip away residue that has ac-cumulated on the roots and can impede nutrient uptake to a degree.Organic growers will also

reap additional benefits from applications of enzyme-based products intended for the root system. These enzymes will noticeably increase the availability of organic nutrient components because they help to solubi-lize organic materials into forms that are more available or “digestible” to the plant. Recently, in working with a grower using these products, it was determined that the enzymes were actually raising the parts per million (ppm) of the growing solution by about 250 ppm over the course of a few

days. This was noted in a drain-to-waste system, where the nutrients were mixed and then applied over the course of a few days between mixing of new batches.Perlite appears to be the medium of choice

for greenhouse and indoor strawberry producers. Compared to a system without a medium, such as NFT, they are much less temperamental and less prone to disaster in the event of a power failure or other stresses to the crop. Using a more medium-based system allows the grower to use a wider range of products throughout the cropping cycle. In European nations and Israel, where protected strawberry produc-tion has been practiced for considerably longer than in North America, growers tend to prefer medium-based production with perlite over other hydroponic sys-tems. Perlite tends to be ideal because it is fast draining, lightweight, near neutral in pH, and relatively inexpensive, and it has li�le or no cation exchange capacity (CEC).Because of perlite’s relative light weight

as a growing medium, it is ideal for use in hanging bag systems. Because strawberries exhibit a low growing and trailing growth pa�ern they are especially well suited to vertical gardens. Vertical gardens maxi-mize the efficiency of the overall volume available for plant production in a given area. Using vertical growth systems allows producers to gain more than 100 percent in efficiency of their floor use. A-frame–type structures such as aeropon-

ics or specialized benching are another option in making use of vertical space, although hanging bags are most com-mon. Some newer designs intended for strawberry production suspend rows of troughs upon which sacks filled with perlite planted with strawberries are sus-pended a couple of meters (~6 �.) from the ground. In this configuration aisles are eliminated. Because the plant growth tends to hang down from the suspended height, greenhouse operators are able to eliminate

>HYDROPONIC STRAWBERRY CULTIVATION

“Average yields per cropping cycle on many commercial strawberry varieties are about two pounds of

fruit per plant.”

Documents

MY USA july aug 2007 - The Planet Fixereco-library.theplanetfixer.org/docs/hydroponics/... · · 2014-12-28Expended perlite can be added to soilless mixes or ... J.B. (2005) Hydroponics: