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UK January - February 2010




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VOLUME 9 – NUMBER 5 JANUARY/FEBRUARY 2009 Maximum Yield is published bi-monthly by Maximum Yield Publications Inc. 2339A Delinea Place, Nanaimo, BC V9T 5L9 Phone: 250.729.2677; Fax 250.729.2687 No part of this magazine may be reproduced without permission from the publisher. If undeliverable please return to the address above.

Speed Read 1. Creating harmony with nature does not need to be difficult. Simply follow the 10 steps set out by Dr. Carole Rollins and you too can enjoy the benefits of a living, breathing, eco-friendly garden (indoors and out). 2. What makes your favourite plants tick? Erik Biksa provides insight on what you need to supercharge plants’ natural processes for faster growth. 3. W  e affect plants, that much is obvious. But do plants affect us to? According to Ethnobotany, the study of the relationship between people and plants, and Luis Bartolo, the answer is yes.

The views expressed by columnists are a personal opinion and do not necessarily reflect those of Maximum Yield or the Editor. Publication Agreement Number 40739092



Behind the Lens: Get those cameras out! Maximum Yield announces our first ever Photo Cover Contest! Send us your best photos to be entered into this exciting contest and have your photo displayed on a Maximum Yield cover. Submit your photos to editor@ Contest details are available on Win Big! Grow Big!: Announcing our biggest contest ever, with sweet grow gear to be won throughout 2010. Enter on by February 15 for your chance at FREE nutrients, fans, filters, lighting and more.

ADVERTISING SALES 250.729.2677 Linda Jesson - Lisa Lambersek - Julie Madden - Ilona Hawser - PRODUCTION & DESIGN Pentti Tikkanen - Alice Joe - Wes Cargill - ACCOUNTING - Lee Anne Veres

Tell us what you think at We’d love to hear from you.


Jose Luis Pinheiro Bartolo is the president of Biobizz Worldwide Inc., a global leader in the production of hydroponic organic fertilizers and soil mixtures. He is passionate about the organic market and providing the highest service and perfectionism that comes direct from his heart and is projected to all aspects of his life.

Erik Biksa holds a diploma in agriculture

Matt LeBannister works at Homegrown

Hans Kersbergen is one of the owners of BAC or Biological Activated Cocktail. Before joining the team in 2003, Hans had his own hydroponic shop for six years. His “How to Grow” seminars run in conjunction with BAC’s products as examples. After five successful years, BAC is expanding and will include their products in Holland, Spain, Germany, Portugal, UK and, in the future, U.S.A.

Hydroponics, the manufacturer of the DNF line of premium nutrients and enhancement products. Matt manages the retail store at Homegrown’s head office in Toronto and as of late has been traveling the trade show circuit as their resident expert.

Mélissa Léveillé holds a license in communication, writing and multimedia. She is responsible for Nova Biomatique Inc.’s communications. Isabelle Lemay is in charge of the technical support, customer service and research and development at Nova Biomatique Inc. ( She is an agronomist and holds a master’s degree in soil and environment studies, with a specialization in greenhouse production. Andrew Taylor is the manager of Flairform

( – an Australian-based manufacturing company. As an analytical chemist with qualifications in plant function and nutrition, he has over 13 years experience in product research and development, and also writes extensively on hydroponic growing techniques.


MAXIMUM YIELD UK - January / February 2010

with majors in fertilizer sciences and crop production. Erik has amassed over 18 years of indoor gardening experience and intensive research. Since first appearing in Maximum Yield in 1999, the “Ask Erik” column and numerous articles have reached growers throughout the world.

Dr. Lynette Morgan holds a B. Hort. Tech.

degree and a PhD in hydroponic greenhouse production from Massey University, New Zealand. Lynette is a partner with SUNTEC International Hydroponic Consultants and has authored five hydroponic technical books. Visit and for more information.

Become a Maximum Yield contributor and have your articles read by 250,000 readers throughout USA, Canada, UK and Australia. Maximum Yield is the largest free-to-consumer indoor gardening magazine in the world. Every issue is available on, which has thousands of unique visitors monthly.

UK DISTRIBUTION Growth Technology Hydrogarden Future Harvest Developments Europe Nutriculture UK CANADIAN DISTRIBUTION Brite-Lite Group Biofloral Eddis Wholesale Greenstar Plant Products Inc. Hydrotek MegaWatt Northern Hydroponic Wholesale Quality Wholesale USA DISTRIBUTION Aurora Innovations BWGS + BWGS West + BWGS East General Hydroponics Hydrofarm Hydro International National Garden Wholesale / Sunlight Supply R & M Supply Tradewinds AUSTRALIAN DISTRIBUTION Dome Garden Supply Futchatec Growth Technology Holland Forge Hydraspher

CONTENTS january / february 2010 FEATURES 22



Keep It Clean: Maintaining Your Hydroponic System


Some Like it Lukewarm: Beneficial Nutrient Environments


Zoo-ponics: The Verticrop Hydroponic System at Paignton Zoo

by Grodan

by Andrew Taylor

by Dr. Lynette Morgan


Worm Power: From Waste to Worthwhile


Pest Control: Organics, Chemicals and Biological Controls


Atmospheric Excellence: If Plants Could Talk


Do Plants Need Climate Controllers?


What is Soil?


C02 Stability and Longevity

by Emma Cooper

by Matt LeBannister


by Hans Kersbergen

by Isabelle Lemay and Mélissa Léveillé

by Luis Bartolo

by Erik Biksa

DEPARTMENTS 4 6 From the Editor


6 Letters to the Editor 8 Ask Erik 10 MAX Facts 14 Product Spotlight 45 Check Your Growing IQ


48 Do You Know? 50 Coming up in March - April MAXIMUM YIELD UK - January / February 2010


FROM THE editor

jessica raymond

We’re beginning 2010 with prizes and contests galore, starting with our Win Big! Grow Big! online reader contest, available exclusively to our UK readers. Enter online by February 15 at We’re also launching our photo cover contest – Behind the Lens – giving you the creative license to shoot the cover photo for Maximum Yield. The winner gets bragging rights and fame as their photo will be seen by thousands of readers around the world. See our ad on page 47 for full contest details. Hydroponics, especially the vertical variety, is making a huge splash in mainstream culture. Finally, business owners are saying YES to hydroponics, their displays of support out in the open, where everyone can see them. These innovative companies include Devon’s Paignton Zoo and a Verticrop hydroponic system that grows food for the animals (pg. 22), and Anthropologie, a fashion retail store in London, featuring a hydroponic wall and 14,000 plants (pg. 10). We’re helping you stay connected to the industry with our E-News delivered to thousands of inboxes monthly, and our ever-expanding Facebook fan page (facebook. com/maximumyield), offering a platform for you to share your thoughts and photos, and debate hot topics of the day. As always, I encourage you to share your thoughts with me by emailing

Jessica Raymond, Editor

letters to the editor Nutrient Nightmare

My Turn to Win Big "It really only covered a basic introduction on what separates hydroponic nutrients from fertilizers."

With so many nutrients available on the market, it can be confusing for growers, beginner and otherwise, to weed through the selection. Because there is so much to cover, I think it would be beneficial to include as many articles on nutrients as possible in every issue of Maximum Yield; or perhaps you could put together a nutrient-only issue, which would cover the spectrum of nutrients available, how they perform, when and how to use them and how to separate the high from the low quality nutrients. Just a suggestion. Thanks Jody Belham

I frequent your website and upon my last visit, accessed your prize contest link. The regulations state entrants must be residents of the United States or Canada. My question is, why isn’t there any contests like this in the UK? Thanks Holly Briggs

January 2010 marks the launch of our Win Big! Grow Big! online reader contest in the UK. Flip to page 49 for more information or visit to enter now.

Worth the Wait Glad to see you finally got the E-News out to your readers. I was pleasantly surprised to find it in my mailbox and full of interesting tidbits. More contests and events, and especially more input from readers and growers like myself would make it truly worthwhile. I would love to see product reviews, real-life photos, industry reports and more grow tips in future editions. Amy Lee

Do I Have to Choose Just One? I loved the seaweed article by Luis Bartolo in Nov/Dec Maximum Yield UK. Come Clone with Us by Kevin Dunlop came at the best possible time for me because I was having issues rooting lavender and rosemary cuttings. Of course, the rest of the articles from recent issues of Maximum Yield UK were also very informative but those were my favourites. Ralph Taylor


MAXIMUM YIELD UK - January / February 2010

Maximum Yield reserves the right to edit for brevity.

We Want To Hear From You! Write Us At: Maximum Yield Publications Inc. 2339A Delinea Place, Nanaimo, BC Canada V9T 5L9 or

MAXIMUM YIELD UK - January / February 2010




Do you have a question for Erik? Forward it to with the words “Ask Erik” in the subject line, and your answer will be printed in an upcoming edition.

Hey guys, I’ve got a quick technical question. I have a 250 MH bulb in a 60 by 90 centimetre grow space for romaine lettuce. If I got my math right, that’s about 42 watts per 30 centimetres. I know that lettuce needs less light than some crops, so is that amount of light too much, not enough or just right? I’ve got it about 60 centimetres above the lettuce. I was also wondering if you could recommend a good online indoor gardening forum for questions like these. There are a lot of them out there, and I would imagine that you know the good ones. Thanks a lot in advance. Eric

Hello Eric, Thanks for the question.You might get some different answers depending on whom you ask. I’m not sure which gardening forum might be best but I would suggest hanging out at your local hydroponic shop. Growers may be able to achieve faster growth rates in traditionally lower light requirement crops such as lettuce by increasing the light intensity, particularly when supplementing carbon dioxide (CO2) levels. However, the additional heat associated with higher light intensities must be managed, as lettuce is sensitive to excessive temperatures and “bolting” may occur. In popular literature, many light recommendations have been made assuming warmer temperatures come with higher light. Today’s grower may not have that same limitation. A light meter would be the best way to determine ideal lighting levels. Different light meters give readings in different units: from micromoles to micro-Einsteins, to lumens. There is much literature available to recommend ideal light levels as per light meter units specified. As mentioned, you may not encounter the same limitations, and choose to push the envelope a bit. If you see the edges of the leaves looking scorched, back off on the light and or temperature. As long as


MAXIMUM YIELD UK - January / February 2010

you can maintain growing temperatures of less than 21°C, the plants should be able to make good use of higher light levels. At a guess, it sounds like you have it right.You might be able to put the lamp closer to the plants, just make sure it doesn’t get past 21°C at the canopy. Remember that watts per centimetre is only an accurate reference when everyone assumes the same distance from the lamp. For a 250 watt lamp, growers requiring high light intensities may have plants as close as eight to 30 centimetres away from the HID source. The MH lamps is an excellent choice, as the spectrum (blue light) may help keep the plants from bolting, even under higher light intensities. Cheers, Erik




hydroponic news, tips and trivia from around the world

Students Seeing Green Following a high-profile campaign by celebrity chef Jamie Oliver, all primaryaged pupils in Newham, east London and County Durham will gain access to free lunches with a twist. Nutritional standards have been put in place for secondary school canteens in an effort to

tackle childhood obesity, so students’ plates will be filled with vegetables and whole grains instead of sugary snacks and treats. School canteens are not allowed to offer meals outside strict calorie limits and must provide foods with a minimum level of iron, zinc, calcium and vitamins. Salt will be removed from tables and foods high in saturated fat and sugar are not allowed. The nutritional standards state a school lunch must contain at least one portion of vegetable or salad and a portion of fruit as well. Even liquids are being regulated to water, low-fat milk and juice. Supported by the Soil Association, a charity that encourages organic

Homegrown Organics with Hydroponics Inspired by a DNA molecule and the increasing use of synthetic fertilizers to boost crop productivity, Rafael Fernando daSilva and Débora Nogueira have designed an indoor hydroponic system. This plant organism provides homegrown organic food and works as a natural sculpture, enhancing health and the owner’s surroundings. The system is based on an NFT hydroponic system, where a nutrient solution is fed from a deposit to the culture channel. It is finished with two vertical metal tubes where germinated seeds of the plants are placed in small holes around the tubes. The watering of the plants is controlled with humid air and a steady water flux. Moreover, the system also features a light system, offering ideal lighting conditions according to the requirement of a particular plant.



MAXIMUM YIELD UK - January / February 2010

farming, the hope is that changes in nutrition will improve behaviour, health and academic standards and even change eating habits in students’ homes. (Source:

Living Large on Regent Street Anthropologie, a United States-based fashion retail store that recently debuted on London’s Regent Street, unveiled a feature wall composed entirely of plants. Approximately 14,000 hydroponically-grown plants cover 457 square metres on a 15 metre high wall. Anthropologie stores in the States are known for their successful hydroponic feature walls, but in the UK, this wall is believed to be the first of its kind. The living wall serves as an impressive centerpiece in the three-floor, 6,705 square metre store, with the plants grown vertically using piped nutrient feeds in place of earth. (Source:

Zoo Food

Paignton Zoo in the UK has created an experimental vertical hydroponic farm as an affordable alternative to feeding the animals using minimal resources. Created by Valcent Products as part of their Verticrop product line, the automated conveyorbased system currently grows lettuce heads, but the hope is to grow a wide variety of crops including red chard, mizuna, mixed leaves and a variety of herbs, edible flowers and fodder crops like wheatgrass. Because the farm imports a wide variety of veggies for their animal feed, this vertical farm will provide a local, sustainable alternative for the zoo’s residents. The system requires just five per cent of the water for field crops, produces 20 times the yield per acre and takes up very little space. The whole set-up has been designed for minimum maintenance with computerized controls to regulate irrigation and water supply. Valcent claim the farm will require one staff member working approximately two hours a day to keep it running, and could cut the zoo’s feed bill by as much as £100,000. Paignton Zoo is carefully recording data and performance of the farm to feedback for further product development. More information on the Paignton Zoo can be found in Dr. Lynette Morgan’s article “ZooPonics” on page 22. (Source:

MAXIMUM YIELD UK - January / February 2010




hydroponic news, tips and trivia from around the world

Health and Wellness for Moms and Tots A new program known as “Healthy Start”, launched by the U.K. department of Health, will provide pregnant women and toddlers from low income families with fruit and vegetables. Piloted in Devon, the new program will cover more than 500,000 low-income families, replacing the current Welfare Food Scheme. The government is providing vouchers worth £2 and 80 pence every week for families with children between one and four years old. Women who are 10 weeks pregnant and mothers with children younger than one year old will receive two vouchers per week. The program is also available to mothers younger than 18, as this demographic has shown an increase in nutritional-vulnerability and are more likely to have babies with low birth weights. More than 20,000 participating businesses will be available to provide advice about healthy eating and breastfeeding. This program means children get the best possible start in life.

Pesticides from Plant Hormones Pesticides are essential at this point for sustaining food production for the world’s growing population. Which is why a recent discovery of a natural plant hormone that can help plants eliminate residues of certain pesticides is so intriguing. Previous research suggested that plant hormones, brassinosteroids (BR), might be the answer to minimizing pesticide residues that remain in food crops after harvest. Scientists in China treated cucumber plants with one type of BR then treated the plants with various pesticides. BR significantly reduced their toxicity and residues in plants. BR could be promising as an environmentally-friendly natural substance for wide application. The substances do not appear to be harmful to people or other animals. (Source:


Grow some Green – Just in time for St. Paddy’s Day Call it the luck of the Irish, but the winter months represent the ideal time for the indoor growing of shamrocks and with St. Patrick’s Day in March, a shamrock seed planted now will be at its peak just in time for picking and wearing with pride for the celebration. The Auld Sod Company is marketing the perfect gift for indoor gardeners. The Auld Sod Box Set is an all-in-one pack that lets the recipient grow authentic Irish shamrocks in a beautifully crafted Belleek bowl with official Irish shamrock seeds. The box set includes: an exclusive handmade Belleek fine china bowl, official Irish shamrock seeds approved by the Irish Government and a one pound pouch of official Irish soil. (Source:

MY 12

MAXIMUM YIELD UK - January / February 2010

MAXIMUM YIELD UK - January / February 2010


PRODUCT spotlight

ask for these exciting new products at your favourite indoor gardening store.

Sure To Grow in Development of the Storm Hail Crouton STG is in late stage development of another revolutionary product to compliment the new Storm series. The Hail Crouton or mini cube, is designed to meet demand from customers and retailers who want to use STG in large bucket and net pot systems. Our STG grow room trials have been very encouraging. Matt the Grower has been all over this and believes this product could be a “game changer”. We have samples out to 10 growers who will field test for us and give us their feedback. If they see the same success we are seeing, expect this product to be available soon. Ask your local retailer to carry the Storm Hail Crouton.

Plagron Alga - Green Gold from the Sea Did you know that algae is the #1 producer of oxygen. It is also jam-packed with vitalizing minerals, vitamins and amino acids. And it’s not just good for people, but for plants too. For these reasons, algae forms the basis of the organic nutrient line from Plagron. And not just any algae is used, but a very special variety found only on the coast of Ireland. These algae rapidly synthesize plant-specific hormones, increasing the speed of plant growth and bloom. In Plagron Alga Grow, algae stimulates better development of the root system, improves plant vitality, serves as a quick start for young plants and protects against fungal infections and high salt concentrations. The hormones activated in the Plagron Alga Bloom help create a lush bloom. The chlorophyll production rises, boosing sugar production and improving taste. Combine the Alga line with top quality soil from Plagron and you have a top 100 per cent organic product. Visit an indoor gardening retail store to learn more.


MAXIMUM YIELD UK - January / February 2010

Field Guides I and II by Dr. Elaine Ingham, compiled by Dr. Carole Ann Rollins

These reference books are for truly dedicated growers questing for scientific knowledge and answers about organic growing, the interface between synthetic and organic growing materials and parameters to follow when using compost tea in either system. Field Guide I is a 171-page compilation about current research on Actively Aerated Compost Tea (AACT) in Field Applications. Field Guide II is a 312-page compilation about current research on Actively Aerated Compost Tea (AACT) in Field Applications. Both Guides are organized into chapters for easy reference about compost tea: mechanisms of impact, effects on diseases, ingredients, brewing techniques, brewers and applications. Ask for these Field Guides at your local grow shop.

Microbe Poster and Manual – Qualitative Assessment of Micro-Organisms The Microbe Poster shows what microorganisms look like using a microscope in 32 colour photos - microbes typically found in soil, compost, worm castings and compost tea - bacteria, fungi, protozoa and nematodes. The Microbe Manual helps you evaluate growing materials qualitatively, and distinguish between the “good guys” and the “bad guys”. The 31-page manual has extremely detailed and scientific explanations of each photo on the poster, with labels to help clarify what you see in each photo and under your microscope. Please contact your nearest indoor gardening store to learn more.

Power Rock from Xtreme Nutrients This is the product you’ve been waiting for! Power Rock is a technological breakthrough in hydroponic and soil grown plants. Flowers gain massive weight and density otherwise impossible. By maximizing the plant’s natural ability to utilize potassium and phosphorus, the plant produces an abundance of five carbon sugars, which get stored in the flowers, adding weight. Used in the fourth week of blooming, Power Rock will increase both the size and the quality of your crop. The flavour and aroma of your crop will improve unbelievably. Power Rock will increase your yield by at least 70 per cent. By using Power Rock the end result will be significantly improved quality and greatly increased yield. Remember, Power Rock is a concentrate; a little goes a long way, so use as directed. Your yield is limited by the products you use; raise your limits with Power Rock. Visit an indoor gardening retail store to learn more.

Stealth Hydro Mistic Clone System Now Available with STG Storm Clipper Clone Puck Stealth Hydro joins a growing number of hydroponics system manufacturers that are now including and recommending STG Storm series inserts as the media of choice for their systems. “Systems manufacturers don’t have a horse in the race when it comes to the media they recommend; media by and large is not a revenue source for them. Their primary concern is that their customers use the best media available, to achieve the best results possible in their systems. Stealth saw better success with the Storm Clipper clone puck than with the neoprene puck they sold for years. It made their system better and they have generated more sales because of it,” says Cary Senders of Sure To Grow. The Storm Clipper fits all clone systems and is the only puck that is designed to be taken from the clone system to the next stage of growth. For more information contact your local hydroponics shop.

MAXIMUM YIELD UK - January / February 2010


PRODUCT spotlight

ask for these exciting new products at your favourite indoor gardening store.

GlowPanel 45® LED Grow Light Featuring all new electronics the GlowPanel 45® LED grow light is now 30 per cent more energy efficient than previous versions with no loss in light output! The new GlowPanel 45® LED grow light sips a miniscule 28 watts of power yet surpasses the performance of a 250 watt HPS. Suitable for all stages of plant growth. The balanced spectrum of the GlowPanel 45® promotes strong root development, rapid growth, tight internodes and bountiful yields. The GlowPanel 45® grows fruits, flowers, vegetables, herbs and more. The GlowPanel 45® runs cool to the touch and emits virtually no heat. Simply plug it in and Glow Your Own® from Sunshine Systems. Ask for the GlowPanel 45® LED Grow Light at your local hydroponic retail store.

A “Hole-in-One” with Green Sensation For 20 years Plagron has been active in the professional guidance of various grow projects, from tomatoes in Sicily to the grass of many European golf courses and famous Dutch football fields. For the hobby grower it started 20 years ago with the famous Plagron soil, the best soil sold in Europe. A few years ago Plagron developed the first real booster for the hobby grower - Green Sensation, a bloom stimulant for the final four to six weeks of flowering. Green Sensation directly supports the sugar production, resulting in a harder cell structure and higher yields. Green Sensation gets maximum results from the plant, improving scent, taste and the pest resistance of the plant. Green Sensation is available in 250 millilitres, 500 millilitres, one litre and five litres. Contact your local grow shop to learn more.


MAXIMUM YIELD UK - January / February 2010

Xtreme Grow from Xtreme Nutrients The latest in technology, Xtreme Grow doubles the size of your plants in four to five days without internodes stretching and cutting a week off your growth program. Should be used in week three or four during the growth period or when the plant canopy is the size of your pot. Eight tablespoons will treat 272 litres of solution and should only be used once. It is very important to adjust pH as this product will drop your pH down to 2.0 to 3.0. Visit your local hydro shop to learn more.

GrowSpot Bloom Booster LED Grow Light The GrowSpot Bloom Booster LED grow light is a supplemental grow light specifically designed to enhance the flower/bloom cycle. When used with HPS, CFL, metal halide, T5, LEDs or other grow lights, the GrowSpot Bloom Booster provides amazing flower power lighting for your crop. The GrowSpot Bloom Booster screws into a standard light socket and runs cool to the touch so they can be placed very near the plant canopy. Available in 15 watts and 110 or 220 volts. Glow Your Own® from Sunshine Systems. Now available at hydroponic retailers.

Agroneem Plus Agroneem Plus is a broad spectrum insecticide that controls over 200 insect species, as well as a large number of nematodes and other plant pathogens. It attacks insects at multiple growth stages, and it’s compatible with most fertilizers, fungicides and insecticides. Agroneem Plus is non-toxic to humans, harmless to beneficial insects and biodegradable. Ask for it by name at your local indoor gardening store.

Early Turn A+B from Xtreme Nutrients Turn growth into bloom, quick! Adapted from use in commercial horticulture, Early Turn has now been perfected for use in domestic hydroponics. Early Turn is a highly potent bloom stimulator that increases the effectiveness of other fertilizers and additives. Early Turn is used in the first (Part A) and second week (Part B) of flowering with two primary actions. The first action is transition. Recognizing the stress on hydroponically-grown plants caused by an instant decrease in daylight hours, we developed Quick Turn to encourage the plants to adapt seamlessly to the new environment and produce flowering sites much earlier. The second action is to stimulate. After the plant has been caringly introduced to the new environment, Early Turn encourages rapid bloom. Early Turn easily stimulates the plant into full flowering production much earlier than normal. This same stimulate increases fertilizer usage and metabolic rate. Visit your local grow shop to learn more.

Nutrilife’s H2O2 Now Available

Adding Nutrilife’s H2O2 is a great way for gardeners to oxygenate the nutrient solution in their reservoirs. A plant’s health and vigour rely on the roots getting enough oxygen, because the roots of a plant need oxygen to convert carbohydrates into energy. H2O2 adds this important element to nutrient solution, effectively “powering up” preexisting feeding regimens. It can also be used to preserve fresh cut flowers and for cleaning reservoirs, drippers and dripper lines. Ask for Nutrilife H2O2 at your local hydro shop today.


You can find all of our products online at Each month your favourite new product profiles will be featured on our website. Get the latest information on what will make your garden grow. Do you want to be included in the product spotlight? Contact the editor at 1-250-279-2677 or email

MAXIMUM YIELD UK - January / February 2010


by Grodan

Keep it Clean: Maintaining your Hydroponic System

Always cut off dead leaves and remove them from the grow room. Decaying organic matter attracts fungus gnats.You should also remove diseased plants, so the infection does not spread. Clean the plant box well with a 10 per cent bleach solution before putting it back in the grow room. When you change water in your stock tank, wash the tank well with a 10 per cent bleach solution. If you use big trays for your blocks and slabs consider washing these too, especially if you have had a problem with root rot. Drippers If you use a drip system buy a few extra drippers, so you can change them if any are clogged up. Have a bucket with vinegar in your grow room and throw the clogged drippers in, so they will be clean and ready to use next time you need to change a dripper. Ebb/flood systems We recommend that you spend an extra couple of dollars and get a timer that can be set at five minute intervals, so a full cycle will only soak the stonewool for 10 minutes. To avoid salt built up we suggest that you top water your plants once per week. Also be sure to have a tray with deep enough grooves so that water drains away from the cubes/slabs. EC and pH The EC level (nutrient concentration) varies depending on the plant stage or how fast your plant is growing. Soil/peat has a buffer and not all you put in is available to the plant. One to two hours before planting, don’t forget to saturate the stonewool with pH 5.5 water. Never go below pH 5.0 or the 18

MAXIMUM YIELD UK - January / February 2010

stonewool may be damaged! Below pH 5.0 and higher than pH 7.0 the plant cannot readily take up nutrient. Immediately before planting flush the stonewool with your nutrient solution. Drain to waste! And then put the stonewool product in your system. Once the plant starts growing the pH in the tank and in the medium will go up. It is a natural response - it means your plant is growing! Stock tank solution We recommend that you completely change the solution once a week.Yes, you can top-up the tank and adjust EC/pH, but your solution may be out of vital micro-nutrients or be infected with pythium (root rot). If your stock tank contains readyto-use (diluted) nutrient solution, please use phosphoric acid (or lemon juice) as pH down. If you have a fertilizer injector connected to a tank with concentrated solution, it is better to use sulphuric acid as pH down. Learn from yourself Consider keeping a journal that lists: the EC, pH, temperature, CO2 and light level each day. This way you can learn from your own mistakes and successes. Records like this also make it a lot easier for the shop to answer your questions when you have a problem

Check the basics Before you blame your plant food for unhappy plants, check your journal. Everything must be in balance. Change one parameter at a time and look for the effect. A common problem is stock water that is too cold. Consider putting a heating element in the tank (to 21ยบC) or put heating mats under the stonewool. If you have trouble getting the plant to set flowers/ fruit, try to make a greater difference between night and day temperatures. If that is not enough, increase CO2 injection during daytime. A common problem If the youngest leaves are curled downward, more than likely it indicates a calcium deficiency. If old leaves are curled; something is probably wrong in the root zone (which also reduces the calcium uptake). Calcium deficiency is the result of insufficient water movement through the plant. Remember, calcium only travels in the water stream of the Calcium deficiency in leaves. plant, not in the nutrient stream. Therefore, calcium deficiency is usually (90 per cent of the time) related to the climate in the growing area. High humidity will prevent calcium uptake even if there is sufficient calcium in the feed solution. Also, large day/night fluctuations in humidity will disrupt the calcium flow within the plant and lead to blossom-end rot (BER). Another cause of BER or obvious calcium deficiency in the leaves is poor root development. This is a result of low substrate temperatures or the presence of a root pathogen such as pythium Calcium deficiency in fruit. or phytophthora. Calcium is taken up by the area of the root immediately behind the root-tip. If the roots are not actively growing, new root tips will not be formed and consequently, calcium uptake will be reduced. Check the Plant! Make a habit of taking a close look at your plants every day. Do they look perky? Look for leaf colour, leaf shape and bugs and then update your journal. If you catch a problem early it can be fixed! MY MAXIMUM YIELD UK - January / February 2010


Some like it Lukewarm: Beneficial Nutrient Environments

by Andrew Taylor In addition to following proper dosing guidelines and controlling pH, EC, etc., it is important to control the nutrient’s environment.

Nutrient temperature It can be beneficial to maintain the nutrient solution temperature within a range of 20-25oC. This will usually be achieved if the air temperature is controlled. Still too cold? A cold nutrient solution (or cold roots) can lower nutrient uptake. If nutrient temperature remains excessively low, a water heater can be used (figure one). Too hot? Hot nutrient can cause disease problems and suppressed nutrient oxygen 20

levels. Small tank volumes can be maintained by placing frozen water bottles directly into the nutrient solution. However, for convenience (or larger tanks), a water-chiller may be required. In either situation, burying tanks underground will provide insulation against extreme temperatures.

Figure Two: Root browning is a typical symptom of the root disease ‘pythium.’

Figure One: Water heaters (left) are useful for heating nutrient in winter. In summer, ‘water chillers’ (right) are effective for cooling. These items can be thermostatically controlled.

MAXIMUM YIELD UK - January / February 2010

Nutrient disinfection It is common to blame the nutrient for poor growth results. However, in many cases, the true cause is poor general hygiene practices, especially the failure to regularly disinfect the nutrient solution. To prevent disease ingress (figure two), the nutrient solution, medium, roots (etc.) should be regularly sterilized. Sterilizing agents must yield a residual chemical when dissolved in the working

Figure Four: Air stones are a reliable method of ensuring oxygen levels are adequate.

nutrient solution so that the entire system is treated each time plants are watered. Historically, chlorine dioxide, sodium hypochlorite and monochloramine are used for this purpose. However, monochloramine has the advantage of possessing a long half-life, is gentle on roots and is compatible with the majority of organic mediums and growth promotants. Oxygenation (Aeration) of nutrient Plants consume oxygen via the roots for the process of respiration. For this to occur the oxygen must be dissolved in the nutrient solution. This is achieved via aeration. Aeration methods: As seen with stagnant water, simply exposing a body of water to air does not aerate it. System design generally determines how much oxygen becomes dissolved in the nutrient. Maximum aeration is achieved by breaking the water up into as small a particle size as possible via a tumbling treatment (e.g. waterfall or fountain). In hydroponic systems, aeration can be achieved by: • Delivering the nutrient solution via spray jets. • Design the hardware (for re-circulating systems only) such that the nutrient splashes into the reservoir when it returns from the roots. In either case though, it is critical to ensure that the air is well ventilated where the aeration occurs otherwise that air will quickly become stale and depleted of oxygen - figure three. An air stone and air pump can also be used. Air stones have the added advantage of promoting circulation of the nutrient reservoir to ensure it is evenly mixed (figure four). Make sure to locate the pump in a well ventilated area. Note: Oxygen also aids in keeping the nutrient sterile due to its mild disinfecting properties. To support optimum plant growth, a nutrient solution generally requires a minimum oxygen concentration of around three milligrams per litre. It is generally noted that

super-oxygenation fails to deliver improved growth results. Also, there is a common belief that high temperatures cause oxygen levels to become inadequate. However by referring to the table one you can see that water can hold seven milligrams per litre of oxygen when at 40oC. Growth problems at higher temperatures could be attributed to photorespiration, increased bacteriological activity, etc. Unrestricted root growth: Because new roots are the main supply route for oxygen, if new root growth is restricted then oxygen supplies will be restricted. Hence, when selecting pots/channels, ensure they will accommodate the likely root volume of the plants when at full maturity. Failure to do so may prevent the plants from reaching maturity. Minimise exposure of nutrient and roots to light Light will accelerate the growth of algae and pathogens. Further, some brands of chelated trace elements can decompose from exposure to UV light which causes them to become unavailable for root uptake. Therefore, minimize exposure to light as much as possible by placing a lid on the nutrient reservoir, and other regions of the system where nutrient is exposed to direct light. In achieving this, ensure the design allows adequate ventilation of air otherwise it will become humid and susceptible to disease. For example, when placing a lid on the reservoir, have it in a raised position so that air can freely enter and exit (figure three). MY

Figure Three: A ‘raised’ lid permits airflow within the reservoir whilst still preventing light and dirt ingress and evaporation. Airflow helps prevent stale air and fungus/molds. A library of Andrew Taylor’s articles can be found on in our author archive.

MAXIMUM YIELD UK - January / February 2010


A wide range of zoo species will benefit from the fresh hydroponic greens grown on site.

by Dr Lynette Morgan


The Verticrop Hydroponic System at Paignton Zoo

Hydroponic plants can enrich the lives of animals just as they do humans, and what better place to exhibit this than at a zoo. Paignton Zoo Environmental Park in Devon, UK, recently hosted the official opening of the Verticrop vertical hydroponic farming system, developed by Valcent EU. The idea of growing fresh food for the animals onsite originated from discussions between Kevin Frediani, curator of plants and gardens at Paignton Zoo, and Valcent Products (EU) Ltd., based in Launceston, who was developing a vertical hydroponic system for high intensity cropping. Space 22

within the zoo was tight and at a premium, so options for on-site fresh food production were severely limited until the vertical cropping was introduced by Valcent. Within a small area in the middle of the zoo, which was formally a goat paddock, a 120 square metre greenhouse was erected in May 2009 and the system began installation in August. By the time of the opening on September 30, an impressive growth rate had ensured some sizeable lettuce was ready for viewing and for taste testing by the zoo occupants. With an annual bill for animal feed currently in excess of £200,000 a year, it

MAXIMUM YIELD UK - January / February 2010

is the hope of management the high intensity Verticrop system will not only produce ultra fresh produce on-site, but also reduce both food miles and food costs for the zoo. Lettuce has been the initial trial crop for the Verticrop system, with many animals enjoying the fresh crunch of crispy green leaves. The zoo currently goes through 800 lettuce heads per week, £8,000 worth of fruit per month and also uses fresh herbs as enrichment for many species. Later on it’s planned that the hydroponic system will have more diversity of crops; currently small volumes of basil and other leafy greens are being trialled.

Grahame Dunling (right) explains details of the Verticrop system at the official opening.

The Verticrop system comprises three and greenhouse control. A ‘touch-screen’ metres tall, multi-level growing trays, which monitor linked to a Priva computer gives are suspended from an overhead track. Each control over the nutrient dosing, greenhouse ‘rig’ consists of eight levels of growing chan- ventilation and the conveyor system. This nels or ‘trays’ of which there are two difsystem allows groups of growing trays to ferent sizes to accommodate various crops. receive different irrigation programs so that Each growing tray, which has been purpose young seedlings or different species can be built for the Verticrop system, has a nutridosed with fewer nutrients than those rigs ent delivery funnel through which nutrients containing larger plants. The Priva system are dosed at the feeding station. The unique also controls the under floor heating system. thing about this vertical system is that the Another interesting feature of the Verticrop rigs are suspended on a closed loop conveyor and in motion around the greenhouse “The 120 square metre greenhouse has track. Each circuit takes approximately 40 the capacity to grow 11,200 lettuce heads minutes with groups of rigs stopping at the using the verticrop system, compared to dosing station on each round where nutrient 4,332 in conventional systems.” solution is delivered via nozzles to the growing trays. The 120 square metre greenhouse system is the custom made tray handler, has the capacity to grow 11,200 lettuce which allows the growing trays to be loaded heads using the verticrop system, compared and unloaded from the rigs, four at a time; to 4,332 in conventional systems. this should allow for commercial Verticrop Nutrient solution flows through the trays, systems to become fully automated. past the plant roots and is channelled to the Based upon technology originally develend were it is collected and drained away for oped in the Valcent Group’s research centre recirculation. The movement of the stacks or in El-Paso, Texas, much of the current success rigs of trays, filled with lettuce plants, around of the system can be attributed to Valcent’s the greenhouse to the nutrient delivery bay UK team led by horticultural development is a feature of the system which has great manager Grahame Dunling, who with many audience appeal as the many spectators who years of experience as a grower and manager pass the greenhouse in the midst of the was fully aware of the challenges involved zoo grounds are testament to. The system in designing high intensity solution culture features not only new technology in terms systems. Grahame’s knowledge and expertise of rigs, conveyors, tray loading machinsaw the development of customized growery and customized growing channels, but ing trays, which are a unique feature of the also incorporates high technology growing system and has made the many modifications greenhouse equipment such as UV nutriand improvements required to get the Vertient treatment, filters and automated nutrient crop system fully operational.

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Zoo-Ponics: The Verticrop Hydroponic System at Paignton Zoo

Kevin Frediani, curator of the plants and gardens at Paignton zoo shows off some of the first harvested crops.

Along with customized growing trays, the system will incorporate the use of the latest technology in soilless growing media. Because the final product is destined to be fed, roots and all to the animals, the media used to raise and support the seedlings needs to be suitable for this purpose. Rockwool has been avoided for this reason, and it is intended that hydroponic seedling media made from a cellulose fibre derived from wood is to be used,

which can be fed to the animals once the animals with fresh produce, but also to crop is harvested. manipulate the nutritional quality of the While growth through summer in the vegetables being grown in the Verticrop multi-level system has been rapid, it system. With hydroponics and protected is planned to trial LED supplemental growing environments, there is much lighting as the season progresses into the more control over plant nutrition than shorter days and lower light levels of the there is with soil grown crops. Starting UK winter.Valcent has been working with a base of good quality water, the in association with Philips to trial new nutrient solution can be manipulated to LED technology which is hoped will influence the compositional quality of the lead to the development of a commerhydroponic crop and whether this is for cially viable lighting arrangement for the animals or for improving human nutriVerticrop system. tion it is an idea Initially several variet“Hemosiderosis is a world wide which has increasies of butterhead and ing appeal to many. problem in zoos where certain loose leaf lettuce were animals, who are no longer dining Kevin Frediani, trialled to determine on the food of their native habitats.” curator of plants which would produce and gardens at the best `fodder crop’ for the zoo animals. Paignton Zoo is particularly interested in While hydroponic lettuce destined for su- the nutritional quality of fresh fodder and permarkets and consumers needs to meet is hoping that the Verticrop system can be specific qualities of long shelf life, comused to address problems such as `hemopact heads and acceptable weight, fresh siderosis’ in zoo animals. Hemosiderosis produce for the animals is a little different. is a world wide problem in zoos where The vegetables, herbs and other produce certain animals, who are no longer dining grown on-site can be harvested and fed on the food of their native habitats, end out immediately, guaranteeing the animals up consuming too much iron, which ends have salads fresher than most zoo-goers up stored in body tissues. This iron builds will ever experience. While there might up in organs such as the liver where it be less of a concern over extended shelf stays permanently and causes severe tissue life and compact heads, there is interest damage over time. While zoo animals can from zoo staff and researchers in using the be fed commercial premixes low in iron, system to not only enrich the lives of the the fresh fruits and vegetables fed to many animals as part or all of their diet typically contain more iron than is needed. With fruit, vegetables and herbs being an important part of not only captive animals diets, but as part of the enrichment and activity programmes, the issue of iron levels and hemosiderosis can become widespread in some species. This problem is further compounded at Paignton Zoo as vegetables grown locally in the deep red, iron rich soils of Devon are higher than normal in iron, and in general commercially-grown vegetables worldwide produced with soil fertilizer additions would be expected to have higher iron contents than the vegetation many zoo animals consumed in their native environments. With hydroponic systems and starting with RO, distilled or rainwater (free from naturally occurring iron in the water supply) it is relatively simple to lower iron in the solution to levels where

Happy customers sampling the first of the hydroponic crop.


MAXIMUM YIELD UK - January / February 2010

The overhead track system allows the rigs of trays to move slowly around the greenhouse to and from the nutrient dosing station.

plant iron deficiency and growth reductions are limited, but the resulting tissue has minimal iron levels, making it more suitable to animals prone to development hemosiderosis. Further manipulations of the nutrient solution and environment could see improvements in dry weight, fibre, vitamin and beneficial nutrient levels, phytonutrients, chlorophyll and other health related factors in the fresh greens that are difficult or impossible to achieve with commercially prepared dried animal feeds. One of the most exciting aspects of the Verticrop system installed at Paignton Zoo is that is it is effectively `taking hydroponics to the people’; zoogoers can walk around the outside of the greenhouse and view the plants moving and growing in situ. This is particularly relevant to Paignton Zoo which is also a botanic garden keen to education people about all aspects of horticulture and the impact on our environment of crop production. Public viewings of large scale hydroponics are rare and while many people are aware of soilless culture, few have the option of seeing high intensity crops growing in real life. At a later date, a web cam installed on the greenhouse ceiling will provide a live feed on the zoo’s website, allowing visitors ongoing viewing of plant progress. Good publicity regarding hydroponics is always a bonus and at Paignton Zoo,healthy lettuce at all stages of development can be seen and the story of how the animal’s lives are enriched by on-site fresh produce is told. The fact that the Verticrop system is the first high intensity vertical

hydroponic system of its kind installed in a zoo anywhere in the world makes it a great addition to Paignton Zoo’s attractions. MY Resources: Paignton Zoo Environmental Park: (, ( Valcent products (eu) limited (

Fresh greens from the Verticrop system are used as part of the zoo’s animal `enrichment’ program. Monkeys and elephants and lions – oh my! Additional views of the vertical hydroponic system and the animals that feed off it are available on

MAXIMUM YIELD UK - January / February 2010


m r o W ! r e w o P by Emma Cooper

From Waste to Worthwhile

Vermicomposting - composting with worms - is an ideal way to turn kitchen waste into nutritious compost for the garden. And you can vermicompost even if you don’t have a garden! A worm bin can be kept indoors, or on the patio, and the compost and liquid feeds produced are ideal for feeding houseplants.

Step 1: Firstly you need a container to keep your composting worms in.You can buy ready-made wormeries, and many of these are very good. Or you can find instructions on the Internet to make your own. The things you need to remember when choosing or building a wormery are that worms are living creatures and have certain requirements.Your worm bin will need drainage and air holes, but you also need to ensure that the worms can’t escape and that they’re kept in the dark.

Step 2: Source your worms.You need proper composting worms - also called red wigglers or brandlings.You can buy them mail order, or get them from fishing tackle stores as they are also used as bait.


Composting worms are used to living in a composting environment, and eat their way through their own bodyweight in waste every day. Regular earthworms don’t like being kept in composters - they like to build burrows underground and remain undisturbed.

Step 3: When you’ve got a suitable wormery, and your worms, you can set up the bin. Add the worms into the bin, with some suitable bedding. If you bought your worms mail order then they may have come with a coir block that you can soak in water and break up. Otherwise you can use shredded paper or something similar, but make sure that it’s damp. Use something organic, so the worms feel at home. It will compost down with the rest of the waste, but that doesn’t matter.

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A worm bin, or wormery, can be kept outside or on the patio, for out of the way convience.

Once you’ve settled the worms, close the lid on the wormery and leave them to get used to their new home for a few days. Resist the temptation to keep lifting the lid - they don’t like the light and you will disturb them. Once they feel at home they are less likely to try and escape from the bin.

worms from the finished compost - they’re native species and will help improve the soil if they get loose in the garden. The population in the wormery will soon recover.

Step 4: You can start to add your kitchen waste a little bit at a time. The worm population will gradually increase to match the available food supply, but at the beginning it’s important not to add more food than they can handle. Too much food will start to rot and smell bad - if that happens, stop adding new waste and let them catch up. Worms love vegetable foods - peelings, tea bags, coffee grounds, even kitchen paper and coffee filters. They don’t like meat, dairy products and fish. They’re also not found of spicy foods and too many acidic foods, so don’t add too many onion skins or citrus peels.

Kitchen waste should be added slowly to allow the worms sufficient time to eat through it.

Step 5: Once your wormery is up and running and you’re adding your kitchen waste, you need to make sure to drain the resulting liquid off on a regular basis so that the worms don’t drown! The liquid run-off is very nutritious, and when diluted (to the colour of weak tea) with water it makes a great liquid feed for houseplants or garden plants.You’ll get much more liquid feed from your wormery than compost.

Crushed eggshells added to your wormery will balance the pH and keep the worms happy.

Vermicomposting is a very easy and efficient process. Once you’ve set up the bin and settled the worms, very little maintenance is required.You should check on the worms at least every couple of weeks to make sure they’re happy in their environment.You may find that the pH sinks too low (the bin becomes too acidic) and the worms try to escape. A handful or two of garden lime, or some crushed eggshells, will help to keep them happy. If you get little flies in your wormery, try wrapping your kitchen waste in newspaper before you add it, or place a layer of newspaper over the surface of the waste in the wormery. Make sure there’s enough moisture in the waste, and that the drainage is working properly and the water level in the bin is not rising. And keep your worms at a comfortable temperature; they can overheat in summer, and freeze in winter, just like us! MY

About the author: Emma Cooper is the voice of the Alternative Kitchen Garden podcast and writes about kitchen gardening and environmental issues. An edible plant geek, she tries to grow her own food sustainably with the help of a reluctant husband and two pet chickens.Visit http://coopette. com for more information.

Step 6: It will be months before you need to worry about removing finished compost from your wormery. The worms will tend to move out of the finished compost and into the newer waste, and you can separate them out when you remove the compost, and then re-start the bin.You don’t have to remove all of the MAXIMUM YIELD UK - January / February 2010


by Matt LeBannister

Pest Control: Organics, Chemicals and Biological Controls Pests are often a big concern for most gardeners. Indoor gardeners find it especially frustrating to battle insects and the others pests that infiltrate their gardens. Insect and pest populations can explode in the pristine, climate-controlled environment that most indoor gardeners grow in. Also within the indoor environment there are no naturally occurring predatory insects to feed on pests and keep them in check. There are many ways to combat these garden invaders before they destroy what is precious to us. There seems to be a ton of different sprays, bombs, traps and dusts available at your local gardening centre to battle destructive garden insects. Some products contain organic, synthetic or chemical pesticides that kill on contact or when ingested. Other options are naturally-derived sprays, coloured sticky traps or an ever-expanding library of predatory insects that can be purchased through local gardening centres and greenhouse supply stores. With so many different types of products to treat any number of pest-related problems, it can be difficult for one to decide which product is right for the job. There really is no right or wrong choice when it comes to fighting garden pests, fungi or mildews; it is up the grower to decide what best fits their situation. With a multitude of options available, it is important to understand how they are properly applied, how they work, which pests or problems they treat and how they affect the plants as well as how they affect us. The best way to make an informed decision is through research and consistent education on the alternatives available. 30

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Once insects, fungi or other pests have infiltrated the grow room, your first line of defence is usually organic pesticides, sprays or homemade recipes.

“Pyrethrum and its active ingredients, should never be used in conjunction with beneficial predator insects, because these pesticides will kill them also.” Pyrethrum and its active ingredients, pyrethrin, cinerins and jasmolins, are a common organic contact pesticide. A contact pesticide kills pretty much every insect or bug that it is exposed to. Therefore, these types of pesticides should never be used in conjunction with beneficial predator insects, because these pesticides will kill them also. Pyrethrum-based insecticides are usually in aerosol sprays or “bug bombs.” Aerosol sprays should be applied to the plant from a distance of one to 30 to 45 centimetres from the leaves. If sprayed too close the leaves will burn, because “Neem oil is extracted by the pressurized contents pressing the seeds of the will escape at a very low Indian neem tree.” temperature. The great thing about pyrethrum-based pesticides is that they are non-systemic.

Aphids on coles.

MAXIMUM YIELD UK - January / February 2010


Pest Control: Organics, Chemicals and Biological Controls

Underside of a leaf with aphids

Systemic pesticides will be absorbed by the plants and cannot be used on crops intended for consumption. Pyrethrum-based pesticides break down quickly and can be used up to three days before harvest. Another very popular pest control product is neem oil. Neem oil is extracted by pressing the seeds of the Indian neem tree. The resulting oil concentrate can be purchased at quality garden stores. Neem is generally applied in a spray to the entire plant. Don’t forget to spray the underside of leaves, because many insects will hide there. The dilution rate for mixing the neem oil is five to 10 mililitres per litre of water. To help the oil and water mix, try adding a couple drops of hand soap; make sure the soap is not antibacterial. When the sprayed neem oil comes in contact with the garden pests, the active ingredient, azadirachtin, confuses the insect’s growth hormones. On young garden insects or eggs this contact will cause the insect to never reach sexual maturity, meaning that no offspring will be produced. Neem oil is effective against spidermites, aphids, scales, fungus gnats and even harms beneficial insects. Neem can also effectively remove powdery mildew and rust. Neem oil should not be used on edible plants that are going to be consumed. Neem oil is a systemic pesticide and will be absorbed directly into the plant that it is being used on. If one does intend to use neem oil on a plant that is edible, it is best to make sure that none of the neem oil comes into direct contact the with fruits or vegetables.

Diatomaceous earth is an excellent organic choice for specifically removing either aphids or slugs from one’s garden. These fossilized remains of single-celled organisms known as diatoms can be dusted on plants and soil. When the diatomaceous earth comes into contact with aphids, the sharp particles will damage their waxy coating, resulting in a fatal wound. When ingested by the slugs, the sharp particles will cut their insides and cause death. Diatomaceous earth is safe to use on all plants, edible or otherwise, although one should wear a dust mask when applying. The little particles can damage human airways and lungs if inhaled. Another pest control product is insecticidal soap. This is a relatively mild form of insecticide made from the fatty acids of plants and animals. It’s most effective against spidermites, thrips, mealy bugs, aphids and any other soft-bodied insect. The fatty acids will penetrate an insect’s membranes clogging them and killing the insect. Insecticidal soaps are safe to use on edible plants as they dissipate in about a day or so. They are a biodegradable and environmentally-safe product. Baking soda (sodium bicarbonate) is a common household product that can be used to treat outbreaks of powdery mildew. When applied to the leaves affected with powdery mildew, the baking soda will alter the pH levels of the leaf surface and kill

“Neem oil is effective against spidermites, aphids, scales, fungus gnats and even harms beneficial insects.”

Spidermite damage



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have aphid midges, whose larva’s saliva will paralyze them so they can cut the juices out. There is literally “There is literally a biological predator a biological predator solution for every pest problem one solution for every might encounter.” pest problem one might encounter. Every predator has a preferred environment it needs to thrive in. Some prefer a hot and dry environment while others prefer it to be cool and damp. The best way to know which one is right for your situation is to do some research on the topic or consult your local hydroponics shop. Using predator insects to combat a pest problem is the safest method and the most natural for controlling insects. Predator A pepper plant with aphids bugs are harmless to plants and humans. When using these biological controls, one should never use any other pest control the mildew as a result. Plants should be dusted or sprayed with a such as sprays or dusts, because any other method will most diluted baking soda/water solution for three days for an effective likely harm the good bugs as well as the bad ones. treatment. There are so many options for removing insects from the Another way to remove powdery mildew indoor garden. There is one for every situation. from plants is to dust them with a mixture of Sprays, dusts, traps, homemade recipes and “Predator bugs are harmless to plants and humans.” powdered sulphur and lime. This method is biological controls are all very effective, as long safe for people eating the fruits and vegetables, as the user is well-informed. Use any pesticide but can hurt the plant sometimes. If the improperly and you and your plants can be at temperature goes above 30°C the leaves with the sulphur/lime risk. So be smart and be safe – your plants will thank you. MY dust on them will burn. Plants can become severely damaged and can even die as a result. If sulphur is to be used to remove powdery mildew the room must be kept cool. A great way to treat your garden pest problem is to use a variety of different homemade pesticide mixes. Many recipes are available online, and most will contain one or more of the following ingredients: chili powder, hot pepper sauce, garlic juices and soap. The soap will clog the membranes of softbodied insects, while the other ingredients like garlic juice and chili powder will confuse insects and make the plant’s taste less desirable. Most homemade mixes are safe to use on fruiting and flowering plants and are non-systemic. Homemade mixes should be sprayed on the underside and topside of leaves twice a week to effectively control and eliminate pest populations. To help control the adult population of winged insects, many gardeners will use coloured sticky traps. These traps use cards that are either yellow or blue and are covered in very sticky glue. The Sources: insects are attracted to the colour and will think that they are The Organic Gardener’s Handbook of Natural Insect and flying towards a flower. When the winged insects land, they are Disease Control. Edited by Barbara W. Ellis and Fern Marshall Bradley. Rodale Press, 1996. trapped to the glue on the card. With no escape, it is only a matter Patten, George Van. Gardening Indoors: The Indoor of time before the pests die. Growing Bible. Van Patten Publishing, 2002. For these sticky traps to effectively trap adult winged insects they should be hung just above the tops of the plants. This is where most insects will fly when going from plant to plant. Probably the best line of defence against a garden insect An assortment of home-made pest spray recipes are exclusively available on infestation is to battle them with predator insects. Every under Online Extras. pest naturally has another pest that feeds on it. For example, spidermites have predator mites that will feed on them and aphids MAXIMUM YIELD UK - January / February 2010


Atmospheric Excellence:

If Plants Could Talk by Hans Kersbergen


Room Temperature The growth and bloom periods of plants are determined by time (12 or 18 hours), and also the colour of lights used (blue=grow period, red=bloom period). Plants will also react to the temperature of the room. The ideal temperature during the growth period is 24째C. This means summer temperatures during the day and in the evening will be warm. In this way, the plants will produce growth hormones, and when autumn starts, the daytime temperature will still be warm with the night time temperatures much cooler. When you keep the temperature in the bloom period 28째C when the lights

MAXIMUM YIELD UK - January / February 2010

are on and 20째C when the lights are off, it is a sign for the plants to produce bloom hormones. Humidity Humidity is one of the most important properties to control in the grow room. In the growth period, you must keep the humidity around the plant about 85 per cent to avoid over-evaporation of cuttings. Focus your efforts on helping the substrate produce strong roots, which will be going in search of water, an action you want to see during the growth period.

The only item you must be aware of is curling leaves, an indication that the leaves have a cooling problem. This can be a direct result of lack of water circulation through the plant via the roots (root pressure) or the humidity in the room may be too low. As your plants grow, they produce more leaves, which signals an increase in evaporation. During this time you must be aware of the grow room’s humidity. A higher humidity causes the roots to work harder at bringing water to the leaves. If leaves start to curl, they need cool water via the substrate. Fans and Air Socks It is very important to create the same temperature and humidity in the grow room every day. How do you do this? Place a ventilator in every corner so that air is blowing in a circle; this circulation will produce a cyclone. The only disadvantage to this is the eye of the

Maintaining an ideal temperature in the grow room signifies plants to produce bloom hormones.

cyclone will be at a higher temperature and humidity than the rest of the room. To control this, simply place your filter in the middle of the room to take away the air. The plants also need fresh outside air, as it contains CO2. Allowing your plants to continue to grow in the evening will provide an additional benefit of 25 per cent more CO2 thanks to assistance from the plants and trees outside. This air must

be brought into the room evenly using an air sock (placed between the filter and the reflectors). When the inlet air is too warm (above 18°C) you must put the air sock below the plants. This air sock is also preventative against all kinds of spores and mites and it muffles a noisy inlet. Water Temperature and Tank Your nutrient solution must be mixed in a reservoir that is dark in colour, as light will influence your water’s pH. Using a cover on the top of your tank will help keep light away. A circulation pump in the tank will help keep the nutrients dissolved in the water. An oxygen pump will provide improved root pressure. Another beneficial tool is a heating element in the tank, assisting with maintaining an ideal water temperature for the plant. The ideal temperature for the plant is 22°C – room temperature of 24°C minus the evaporation of the plant – this is around two or three degrees). When the water quality is very poor use a filter or bring down the hardness of the water with a pH nitrogen minus (acid eats lime). Don’t use the water too long (two or three days) because it will get warmer (lose oxygen) but also the pH of the water will rise. EC and Flush When salts build up in your substrate, it takes water away from the roots, causing them to have to fight for hydration. A domino effect then occurs, as the roots cannot get water quickly enough to the leaves and they start to curl. If this continues for a long period of time, the leaves will burn. Salt build-up is the result of improper nutrient ratios or a concentration of bad salts (chloride, sodium). Many growers flush their system when they start to see leaf curl, which they blame on too much nutrient. The best way to counteract leaf curl is to check the water levels in the substrate. If it is too dry, you can lower the EC in the water tank. But don’t forget to keep feeding.

As one of the most important properties to control, a proper humidity helps avoid over-evaporation.

By neglecting your nutrient schedule, other problems will arise. Flushing can also create pythium (root rot) and long, stretching plants. Watering Watering of the plants depends on your climate; this includes the humidity, temperature, EC and air movements (in and out). When you follow a feeding schedule exactly you will see your plants MY evaporate appropriately.

Hans Kersbergen’s past articles, which include his popular threepart series “Grow Your Own – a Dutch Perspective” can be found by searching this author on

MAXIMUM YIELD UK - January / February 2010


Do Plants Need Climate Controllers? Gardeners all have the same goal in mind; to obtain maximum yields in a short time frame. To succeed, it is necessary to understand your plant’s needs and to cultivate them in the ideal environment. This article serves to expand your knowledge on plant’s needs and climate controllers that ease gardener’s tasks.

by Isabelle Lemay agr. and Mélissa Léveillé


MAXIMUM YIELD UK - January / February 2010

Gardeners all have the same goal in mind; to obtain maximum yields in a short time frame. To succeed, it is necessary to understand your plant’s needs and to cultivate them in the ideal environment. This article serves to expand your knowledge on plant’s needs and climate controllers that ease gardeners’ tasks. Plants are organisms that operate like a factory. For efficient production, specific processes must be adhered to. The grower must provide the primary elements needed to produce a quality finished product, and do so in the best environment possible. Comparably, the growth of a plant depends on biochemical procedures such as photosynthesis and cellular respiration. A well balanced process counts on the primary part’s availability and the quality of the environment. Photosynthesis Photosynthesis is a bio-energetic process that occurs in plants which converts carbon dioxide into organic compounds using the energy from sunlight or a light source. As a result plants create carbohydrates, very energetic organic substance, and release oxygen (O2). Photosynthesis happens in the presence of light only. Cellular respiration Once the carbohydrates are synthesized, this “fuel” must be transformed to supply the plant’s cell with enough energy to function normally; this is called cellular respiration. Opposite to photosynthesis, this reaction does not depend on light; instead it occurs in both the light and dark.

Glucose (C6H12O6) + Oxygen (O2) X Carbon dioxide (CO2) + Water (H2O) Net photosynthesis


Photosynthesis gains

Cellular respiration loss

Photorespiration* loss

Growth In addition to being crucial to cellular respiration, carbohydrates are also an essential element for the plants to create fat, oil and other organic molecules. The plant’s growth is a result of the net photosynthesis which goes as such: MAXIMUM YIELD UK - January / February 2010


Do Plants Need Climate Controllers?

*Photorespiration is a process that happens simultaneously with photosynthesis from which energy and oxygen are used by the plants and transformed into carbon dioxide. To grow, plants also need water, mineral elements absorbed from the roots as well as other resources necessary to photosynthesis. Primary parts As mentioned previously, identical to a factory, the plant needs raw material to produce. Even if a factory develops and applies the best processes, it will not produce anything without the primary components. Plant’s supplies come mainly through the leaves and roots. Not only the presence of those elements is important but their concentration and proportion must be considered. Unwanted effects might occur if unbalanced concentration of these elements is present. Environment Continuing with our example, a good factory manager will ensure a work environment favourable to production. He will closely study the equipment’s disposition, quality of the tools, lighting, climate and much more. In the same way, the gardener will consciously know that the garden’s environment will RELATIVE HUMIDITY Affects the plant’s transpiration process, in which water evaporates by the stomata (a stoma [also stomate; plural stomata]: a pore, found on leaves and stem’s epidermis used for gas exchange). The drier the air, the greater the water loss; the higher the relative humidity level, the lesser the plant’s water exudation. Transpiration is essential for minerals and water absorption from the roots; no absorption without transpiration. Excessive transpiration (low air humidity) may cause withering (lack of water) and close stomata, photosynthesis is slowed down or stopped.

TEMPERATURE Influences many processes (e.g.: photosynthesis) and growth. The ideal temperature for photosynthesis depends on many factors such as vegetal species, light intensity and CO2 concentration.

AIR CIRCULATION Increases CO2 concentration towards leaf area. Allows better light penetration. Results in an increase of photosynthesis. Strong wind may cause withering and stomata closing.


Essential to photosynthesis. Stimulates the opening of stomata, which increase transpiration and allows gas exchange necessary to photosynthesis. Light intensity varies with plant’s species.


Parameter with many sub-factors: Temperature Mineral element’s concentration (electrical conductivity) pH Air content (required for root’s oxygen absorption) Water availability


MAXIMUM YIELD UK - January / February 2010

influence the photosynthesis process and cellular respiration, which have an important impact on his harvests. Many environmental aspects influence the plant’s growth such as relative humidity, temperature, air movement as well as lighting and the growing media. Each of these factors might have different effects on plants; here is a few of them: Thoroughly understanding environmental effects on plants is not an easy task. Other than the ones discussed, we have to consider some interactions between some effects. This means the improvement of one factor will not necessarily augment the photosynthesis process until other conditions are favourable and complementary as well. For optimal photosynthesis, we have to perfectly balance lighting, temperature, relative humidity and CO2 concentration. Please note that an augmentation in photosynthesis will also increases the plants other needs like water and nutrients! A growing interest for indoor gardening Due to the complexity of the elements discussed, many choose indoor gardening to better control their garden’s environment. This way they can aim for faster growth and maximum yields with higher quality. The indoor gardening concept comes from greenhouse gardening which has created deemed the term and idea of Controlled Environment Agriculture (CEA). In both cases, the goal is to provide an artificial environment favourable to plants in order to obtain superior results with numerous high quality

crops. Indoor gardening seems to provide a better closed in artificial environment since gardening in greenhouses does not normally allow lighting control and is often not as well isolated as is a room. Remember that optimal results come from a precise control of the environment and the gardener’s close attention. Why use climate controllers? It is possible to control our indoor garden’s environmental conditions. However, a manual management of your garden might be difficult and plant’s precise requirements might not be reached. This is why there are climate controllers to automatically regulate your environment. These controllers, like all automatic control systems, work with control loops. They are composed of detection mechanisms (e.g. probe or sensor measuring temperature), a regulator (compares the measurement to the set point and send command signal) and an activator (interprets the command in action, for example, sending an electric current to the output activating equipment). Different types of controllers There is a wide variety of climate controllers to fulfill many gardening needs. We can classify these controllers in two main categories - specific controllers (one function) and integrated (multiple function) controllers. Specific controllers manage only one climate correction at a time. Thermostat, hygrostat and CO2 controllers are found in this category like lighting or irrigation timers. Specific controllers might be recommended for beginners. They allow to gradually understand the climate conditions and to equip their garden sparely to avoid spending a large amount of money at once. The number of specific controllers required will depend on how many aspects of your garden you want to manage. Remember, a greater number of controllers in a garden equals a higher complexity. Noticeably, some actions might be complementary while others will be contradictory. For example, using a blowing fan at the same time as a CO2 generator will allow the gas to reach the leaves. On the other end, venting the room with exterior air would evacuate the generated CO2. For interrelated process, it is recommended to use integrated controllers. These controllers called “intelligent” can be programmed to take in consideration complementary actions or contradictory ones. They assure a better climate management and great energy savings. Controller’s quality Many factors are to be considered when it comes to quality and some are more important than others. Sensor precision is

a major detail to contemplate when purchasing a controller. Sensors can be mechanical, analog or digital. Mechanical sensors are cheaper but do not provide great precision towards their reading and high range differential;

“Some [controller’s] actions might be complementary while others will be contradictory.” they do not provide the kind of tightly controlled conditions required by plants for optimal growth. Unfortunately, they are still in wide use by some horticultural controller manufacturers offering low cost products. They are easy to recognize as the setting(s) and knob(s) advance by increments making a distinct “click” noise. Analog and digital sensors lie on electrical variations that are in direct relation with the measured parameter. When the controller’s programming and the electrical data is well interfaced, the controller will be noticeably precise. The controller’s quality also depends on its other components. The precision level relies on the electrical technology’s quality used from the manufacturer. Offered functionalities are another MY For an easily-downloadable table on the environmental aspects that influence plant growth go to

MAXIMUM YIELD UK - January / February 2010


by Luis Bartolo

"Cimate, vegetation, time, surrounding terrain and human activities influence how soil is formed."


MAXIMUM YIELD UK - January / February 2010

"The development of soils by man (agriculture) is one of the most influential factors of why soils differ regionally."

Soil is one of the three major natural resources, alongside air and water. It is a marvelous product of nature and without which there would be no life. Soil is made up of three main components – minerals that come from rocks, organic matter which is the remains of plants and animals that use the soil and the living organisms that reside in the soil. The proportion of each of these is important in determining the type of soil that is present. But other factors such as climate, vegetation, time, the surrounding terrain and even human activities (e.g. farming, grazing, gardening etc.), are also important in influencing how soil is formed and the types of soil that occur in a particular landscape. Soil can form from the rocks below or from rocks a very long distance away - perhaps being carried by wind or water. The glaciers of the last ice age acted as giant bulldozers pushing huge amounts of soil along as they grew and dropping the soil as they melted. Soils of the world Did you know that there are thousands of different types of soil across the world? The United States alone possesses more than 20,000 varieties. In this section you will find out

about the main reasons why soils differ regionally, as well as soil mapping and the numerous attempts that have been made to classify them. Why do soils differ? There are numerous reasons why soils differ regionally. The most influential factors include the parent material (the rocks from which the soil has come), the climate and terrain of the region, the type of plant life and vegetation present and, of course, human influence. Parent material - this refers to the original underlying rock upon which the soil formation takes place. Essentially, the nature of parent rock in a particular region will affect the type of soil that eventually develops. For example, in an area of mainly sandstone, the soil formed due to the weathering of the rock is likely to be well-drained, course and sandy. Climate – The world consists of a broad range of climatic regions, each with its own specific types of soil. A common example of this is tundra soil, which tends to occur mainly in northern-hemisphere areas such as the Arctic and Scandinavia, where the climate is often cold, the organic materials do not break down easily and peat tends to form. In contrast, red and grey ‘desert’ soils which are found only in hot, arid regions, such as Africa and the Middle-East,

MY MAXIMUM YIELD UK - January / February 2010


What is Soil? contain very small amounts of organic material because it is rapidly oxidized under the warm conditions. These soils tend to leach less than the tundra soils. Terrain – this is another important factor in soil development. Areas with many slopes in the land tend to have more freely drained soils, as water can run off or percolate more rapidly. In contrast, regions with mostly flat areas of land can often be waterlogged, because of the lack of gradient to promote lateral or sideways flow. Plants – The type of plant life and vegetation obviously varies according to a region’s climate and other factors. Plants also have a strong influence on soil development; they take up nutrients from the ground, whilst adding organic material to the soil surface. Humans – We should not forget the influence of man who has managed the land over the last few thousand years. Agriculture, in particular, has had a big influence on developing the soils we see today. Soil Classification Over the years, there have been numerous attempts to give names to soils and to group them into natural classes, in much the same way as plants are named and classified. Classification is important in order to allow comparison between the soils of different regions, and to facilitate information transfer and organization of the growing knowledge about the main types of soil that occur around the world.

"Although the American and FAO systems of soil classification are widely discussed and referred to, many countries still use their own national classification systems." The first true soil classification was produced in the second half of the 19th century by Dokuchaiev in the USSR. Dokuchaiev suggested a theory of ‘zonal soils’, where soil types came from clearly defined geographical and climatic locations. In 1953, Kubiena produced a system of classification that proved to be popular and is still widely referred to. His system consisted of five main soil groups (and many sub-groups), arranged according to specific horizon classes, as well the type of ‘humus’ present. Influenced by Kubiena’s ideas and other previous classifications, two international soil classifications have been developed since the 1960s, the American ‘Seventh


MAXIMUM YIELD UK - January / February 2010

A SOIL PROFILE Horizons 0” O 2”

A 10”



C 48”

Approximation’ classification system published in 1960, and the Food and Agriculture Organization classification in the 1970s. These have been many attempts to provide a unifying classification as a basis for technology transfer, but this has been hindered by the use of new, often complex terminology for describing soils. For example, the American class names in their system include the terms ‘entisols’, ‘inceptisols’, ‘aridisols’, ‘mollisols’, ‘spodosols’, ‘alfisols’, ‘ultisols’, ‘oxisols’ and ‘histosols’, which to the layman may not mean very much! Although the American and FAO systems are widely discussed and referred to, many countries still use their own national classification systems by preference. It is incredible to think that there is still so much that is unknown about soil types, and that new discoveries are continuously being made all the time. Unfortunately, there is still no universal standard for soil classification, although the recent World Reference Base (WRB) for soils may address this in the future. Soil and the Economy Soil plays a crucial role in the economy of countries. Farming and agricultural industries are probably the most reliant upon soil, particularly in respect to crop production, which has risen dramatically in the last 50 years in order to cope with the demands of an equally rapidly growing global population. The demand for more crops has increased the demand for plant nutrients in the form of fertilizers. For a long time, many farms relied on animal manure for this. However, most farms in the west now use artificial fertilizers, because it allows for more control over which nutrients should be applied to the soil and when. In the developed countries of the world it has been possible to increase the productivity of soils immensely because of the introduction and development of such fertilizers For example,

the use of nitrogen fertilizers has increased 15-fold in the UK in the last 50 years, and over the same period yields of some crops have trebled. Research conducted into crop growth, and how soils release nutrients to plants, has enabled farmers to use suitable and better adapted fertilizers for different crops and soils, and thus add to the fertility of their soils. There are many other economic land uses that are dependent on the soil, particularly forestry. Trees are usually longer term ‘crops’ in which an important relationship is built up with the soil to establish a nutrient balance. Organisms in the Soil It is hard to believe that a single teaspoonful of soil contains over four billion micro-organisms, which is more than half of the planet’s entire human population! Can you even begin to imagine how many you would find in a garden, or even your nearest park? Soil is populated by an amazing variety of living creatures, ranging from tiny microbes such as bacteria and fungi (microbeasts), to smaller insects such as centipedes and other animals such as worms (minibeasts) and larger animals such as moles and rabbits.

An abundance of living creatures populate soil, performing important roles like decomposing organic matter.

Many of these organisms have very important functions. For example, certain microbes can break down resistant organic matter such as lignin, or chemicals such as toxins and pesticides. Others perform a similar process on minerals, thereby releasing nutrients for the plant. Bacteria, an essential group of soil micro-organisms, are responsible for much of the decomposition of organic material in soils. They are usually present in top soils in very large numbers and play an important role in converting more inert forms of nitrogen to ones that can more readily be taken up by plants. Earthworms are another vital species, because they help in the decomposition of organic matter in the soil, as well as improving vital functions such as aeration, water infiltration and drainage. In fertile soils they can number two million per hectare or more! When it rains, worms will come to the surface so they don’t drown. Go and look!

MAXIMUM YIELD UK - January / February 2010


What is Soil? Soil and Water There is an important link between soils and water, the quality of our water being closely linked to the quality of the soils. Water in the soil supplies plants and animals, but acts also to transport nutrients and other important substances from the soil to plants and microbes. However, too much water can have damaging consequences. For example excessive rainfall can result in problems like soil erosion, and can waterlog plants and vegetation thus depriving their roots of air. Thankfully, certain

"Farming and agriculture has risen dramatically in the last 50 years in order to cope with the demands of a rapidly growing global population." properties of soil can reduce the possibility of this happening. There are several stages in the interaction of water with soil. Firstly, it enters the soil through a process known as infiltration – the higher the rate of infiltration, the more water is soaked up by the soil, and will be available to plants. Also, less water will run off the surface, eroding the soil and washing away nutrients. Secondly, water is stored in the soil and released when required by plants. Following this, drainage (percolation) of the water occurs when there is too much for the soil to cope with. The excess water drains freely out of the soil, taking with it dissolved and suspended material in a process known as leaching. Soils can vary greatly in their ability to perform these functions. Pollutant Control Another amazing feature of soil is the way it acts as a ‘filter’ against many forms of harmful substances (pollutants). Research by soil scientists has shown that soil can have a major role in the transport of pollutants. Water in soil can transport substances such as nitrate, phosphorus and pesticides to water sources such as rivers, and whilst they are important to soil and plant life, these materials are generally considered harmful to humans and wildlife when they exceed certain quantities. However, soils can also modify the impact of pollutants. For example, in wet conditions soil nitrate is converted into nitrogen gas, where it can be safely released into the atmosphere. Similarly, pesticides can be broken down into harmless substances by certain micro-organisms present in the soil. Phosphates are mostly filtered naturally during drainage of water (percolation), as they become tied to soil particles, and are trapped in the soil. Soil is also effective at filtering ‘urban’ pollutants like oil and metals. Oil in particular is an organic substance, which soil microbes can break down into carbon dioxide and water. Metals such as lead from petrol, however, cannot be broken down in such a manner, but the soil can often retain them until they can be absorbed into plants, which can then be disposed of safely. 44

MAXIMUM YIELD UK - January / February 2010

With over four billion micro-organisms contained in one teaspoon of soil, imagine how many exist in a handful?

Soil and Archaeology Soil is very important for archaeologists, because it provides a source of information about past climate, vegetation and animals (ecofacts), as well as man-made artifacts such as ancient metal tools, coins etc. Soil can preserve all kinds of things for thousands of years. However, its ability to do this depends on the soil conditions, especially the amount of water present in the soil throughout the time the items are buried. Waterlogged soils are particularly good at preserving objects, because they contain very little dissolved oxygen, which is needed by the soil organisms responsible for decay. Searching for ‘ecofacts’ such as plant and animal remains, is a useful means of reconstructing how the ecology and environment of the surrounding land may have once been, and how it has changed. Fossilized snails and insects are particularly good for estimating past climate, whilst preserved pollen grains and seed can reveal which plant species made up the natural vegetation. Additionally, soil and crop marks (best visible from the air in dry weather) are good indicators of past use of the land. These markings generally appear due to different levels of crop growth caused by buried structures such stone-walls and refilled ditches.


CHECK YOUR growing I.Q.

by Erik Biksa


1. Which of the elements in the list below is commonly mistaken to be deficient in supply, when typically the causal agent of the symptoms is more often related to pH? a) calcium b) magnesium c) nitrogen d) potassium

4. Why do both coco coir and rockwool medias require special considerations with regards to pH, noting that the greatest consideration is with rockwool?

2. What is considered to be the optimal pH range for absorption of this element in hydroponic (water culture, excluding rockwool) systems (while considering the availability of all nutrients)? 3. What is considered to be the optimal pH range for absorption of this element in soilless (water culture, excluding pure coco coir) medias (while considering the availability of all nutrients)?

5. Scientists rate surfactants according to the HLB of their molecular structure. What does HLB stand for? a) hydrophillic lipophillic balance b) hot looking babe c) holding lipidic balance d) none of the above 6. If the HLB scale is between one and 20, in most horticultural applications it is best for surfactants to be in the _______ portion of the HLB range. a) low b) mid c) high

ANSWERS: November/December 2009 quiz


1) c, 2) a, 3) because ppm is a conversion from EC. Different manufacturers use different conversion rates, making it far less of a universal measurement. 4) a, 5) d, 6) a, answers to this quiz will be printed in the March/April 2010 issue of Maximum Yield. MAXIMUM YIELD UK - January / February 2010


Stability and Longevity

by Erik Biksa

The question on the table today is, does CO2 go “stale”? Most substances, and molecules for that matter, are in a constant state of flux and are changing states, or the way they are formed on an atomic level. Arguably carbon may be one of the most stable molecules we have, and it’s a very important one. However, carbon dioxide is not just carbon, it is CO2 so there are two oxygen molecules attached, and oxygen can be relatively reactive. O2 as a compound offers a little more stability than something like O3, which is ozone. The extra oxygen molecule wants to leave the arrangement, as O2 is more stable. In most indoor growing situations, the CO2 in the growing atmosphere gets used up astonishingly quickly when plants are healthy and productive, and also depend on the stage the plants are at in the cropping cycle. This is why it makes good sense to enrich the environment with a supplemental source of clean carbon dioxide if ventilation through outside air exchange is not constant during the lights on cycle. Ensuring that CO2 levels remain higher than ambient through various stages in the cropping cycle can increase yields by as much as 30 per cent and often reduce the overall amount of cropping time required, because plants produce at accelerated rates. In most situations, it seems that the most likely scenario is that the additional levels of CO2 will get used up faster than they may be able to degrade. However, it’s doubtful that any carbon dioxide enrichment system is 100 per cent efficient, meaning that other less desirable compounds may be introduced as gases when delivering elevated carbon dioxide levels to crops. For example trace amounts of ethylene and carbon monoxide


MAXIMUM YIELD UK - January / February 2010

In most indoor growing situations, the CO2 in the growing atmosphere gets used up astonishingly quickly when plants are healthy and productive.

may be introduced using gas-fired CO2 generators. Since the plants do not want to use or absorb these gaseous compounds, they may build up to harmful levels in a tightly sealed growing environment; becoming toxic to plants. Also, for gas fired burners (CO2 generators) to work efficiently, they require a source of fresh air for the combustion process. Savvy operators of CEA (Controlled Environment Agriculture) or sealed grow set-ups allow for a slight “bleed” of the air to occur. For example, to ensure a very healthy growing atmosphere, a proportionately small, passive fresh air access is created and is “capped” off with a HEPA intake filter, as featured in some of my articles. With a carbon scrubber (activated carbon filter with fan) cycling constantly within the area, it will pull a small amount of fresh air into the grow room through the small passive HEPA intake. Excess air will “leak” out of the growing environment through any tiny cracks, etc. Remember it’s almost impossible to 100 per cent seal a room, so there are some cracks for the air to bleed out. The volume of fresh air being introduced is cleaned through the HEPA filter and does not introduce contaminants, just enough fresh air to help displace stale air or gases that can accumulate to toxic levels. Imagine a full glass of water that has a few drops added every minute; the volume of liquid will slowly be exchanged over time, keeping it fresh and palatable. MY A HEPA filter can clean the air Passive, fresh air can be introduced to the grow set-up by using a HEPA intake filter. When combined with a fan that cycles air through the environment, the filter will help to remove any contaminants and provide a healthy growing atmosphere.

MAXIMUM YIELD UK - January / February 2010






The Paignton Zoo in Devon, UK currently spends in excess of £200,000 a year on animal feed, and goes through 800 lettuce heads per week, the majority of which is imported.


Air circulation in the grow room has a number of benefits including, increasing CO2 concentration towards the leaf area, allowing for better light penetration and increasing photosynthesis.


Beyond rinsing twice a day, sprouts like broccoli and wheatgrass need very little attention, making them a great addition to a kitchen garden.


The first true soil classification was produced in the second half of the 19th century by Dokuchaiev in the USSR, who suggested a theory of ‘zonal soils’, where soil types came from clearly defined geographical and climatic locations.


The Merriam-Webster Dictionary defines substrate as “the base on which an organism lives.”

4 5


Simply exposing a body of water to air is not enough to aerate it. Maximum aeration is achieved by breaking the water up into as small a particle size as possible via a tumbling treatment (waterfall, fountain).

Salt build-up can be avoided in ebb and flood systems simply by top watering plants once per week.

Keeping the humidity in the grow room around 85 per cent will help avoid over-evaporation of small cuttings.

MAXIMUM YIELD UK - January / February 2010

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COMING UP IN MAX-MART march-april 2010


Fads and Fallacies Often propagated on Internet forums, William Texier attempts to debunk some of our industry’s most well-recognized myths, examining products that when misused can be potentially damaging.

Weird Plant Happenings Dr. Lynette Morgan scrutinizes strange plant happenings that can be fascinating and completely natural, and also frustrating in some instances.

Container Herbs for Beginners From thyme and mint to rosemary and oregano, our favourite Brit from Oxfordshire Emma Cooper details annual and perennial herbs perfect for beginners.

Selecting and Maintaining Mother Plants Preserving your favourite plant strains through cloning is easy with help from Matt LeBannister in this quick read.

Wind, Earth, Water or Fire: Which CO2 are you?

Erik Biksa discusses the four methods of delivering increased levels of CO2 to the grow room in order to increase growth rates, give bigger yields and reduce overall cropping time.

You Tell Us Maximum Yield discusses the beneficial qualities of light reflective film for growers and maximizing light supply with Simon Atkinson of Easy Grow. UK-Exclusive Contest – Win Big! Give your grow the best with prizes from top UK manufacturers in our Win Big…Grow Big online reader contest. Enter online at big throughout the year for your chance to win, and keep reading Maximum Yield UK for more information on this and other giveaways.

Check to stay informed about upcoming 2009 and 2010 Indoor Gardening Expos.


MAXIMUM YIELD UK - January / February 2010

Maximize your exposure with Max-Mart! Get your ad in the next issue of Maximum Yield Call 250-729-2677 for more information

UK January - February 2010




What is


Maximum Yield UK - Jan/Feb 2010  
Maximum Yield UK - Jan/Feb 2010  

ydroponics gardening resources by Maximum Yield, a free how-to hydroponics gardening and indoor gardening bi-monthly magazine that is distri...