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AUSTRALIA November-December 2009

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The nutrition of your plants

Essential Points by Luis Bartolo

Plant Growth Processes Plant growth processes are the subject of many studies by plant physiologists and biochemists. A comprehensive account of these processes is outside the scope of this present work, the object of which is to deal with the outward and visible signs of imperfections in the plant activities caused by faulty mineral nutrition. Nevertheless, it is useful to understand the main processes involved and to realize that the symptoms we shall be discussing later have a physiological basis. They are not direct and unchangeable signs of the specific deficiencies but result from the derangement of the complicated mechanism of the plant’s vital activities. The main processes involved in plant development may be summarized as follows: Absorption: Intake of water and mineral elements by the root system. Carbon assimilation or photosynthesis: Intake of carbon dioxide from the air by the leaves, and reaction of gas with water in the leaf in the presence of green chlorophyll to form sugar and free oxygen. Formation of protoplasm: Protoplasm is the living material of the plant, consisting mainly of proteins, complex compounds of nitrogen built up by the plant from more simple compounds of this element. Respiration: The combination of oxygen with various food substances synthesized by the plant, especially sugars, whereby energy is produced. Transpiration: Loss of water from the plant, mainly from the leaves. Translocation: The movement of materials within the plant. Storage: Storage of reserve products in various organs and tissues. During growth there is a continuous building up of complex compounds of carbon and nitrogen and breaking down of these into more simple 26

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substances, in which water and oxygen are intimately concerned. These processes together comprise plant metabolism. In the course of the metabolic processes, innumerable substances are formed such as sugars, starch, cellulose, acids, lignin, tannins, amino acids, proteins and amides. Many plants also produce special products, for instance nicotine in the tobacco plant. For the normal functioning of the above processes there must be an adequate intake of water by the plant to maintain the plant cells in a more or less turgid condition. Since water is being continuously lost at a varying rate from the plant, intake and movement within the plant tissues must be capable of quick adjustment to these changes. As a result of metabolic activities, plants develop special organs of growth and reproduction, each of which has its special characters and makes particular demands on the nutrient supplies of the plant. With all plants there are well-defined seasonal growth cycles. Annuals such as cereals begin from the seed and give rise to seedlings, which later flower, form grain and ripen off. Perennial deciduous trees such as apples and pears begin growth in the spring. They use stored reserves of food, form leaves, make shoots, blossom, form fruits and subsequently, shed their leaves, but meanwhile pass on reserve foods to various storage organs in preparation for the next season’s growth. Coincident with these growth cycles, there are well-defined chemical cycles of nutrient elements and elaborated products in the leaves, stems and roots. It will be shown later that these cycles are of great importance in considering phosphorus deficiency effects and in diagnosing their causes. The Plant Environment Nutritional problems must be considered in relation to all the conditions in which plants live, and not merely in terms of the amounts of plant nutrients contained in or added to the soil. For example, those who are accustomed to growing plants know that low temperatures may result is no growth and high temperatures may result in injured plants. An optimum temperature may vary depending on whether the plant is young or old. Similarly, light is of great importance and plants may be put in special positions to obtain a maximum supply of light at one stage and may be shaded at another. MAXIMUM YIELD Australia - November/December 2009

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The Nutrition of Your Plants: Essential Points

“Perennial deciduous trees begin growth in the spring. They use stored reserves of food, form leaves, make shoots, blossom, form fruits and shed their leaves, but meanwhile pass on reserve foods to various storage organs in preparation for the next season’s growth.”

Cherry blossoms

The actual duration of the daily period of illumination also affects growth. There are plants that are classified as requiring “long day” conditions to complete their growth cycles and others that need “short day” conditions. If the special long or short day periods are not forthcoming for the respective classes of plants requiring these, their growth cycles are abnormal and they may fail entirely to produce flowers, grain or fruit. The humidity of the atmosphere, as distinct from the water supply in the soil, is of importance in determining the water conditions within the plant. These are dependent on both water intake by the roots and water loss from the leaves, the latter being largely influenced by the air humidity. Even the presence of adequate quantities of plant nutrients in the soil is no guarantee that the plant roots will absorb them. However, even when they would be considered as being present in suitable forms for absorption, other factors may prevent this from taking place. An example of this latter condition is afforded in poorly aerated soils where lack of oxygen near the roots may prevent them from actively absorbing mineral nutrients. The problems of such influences in the plant environment are complicated by the fact that they do not act independently, but their effects are modified by one another. Thus, the effects of light intensity or period of daylight may vary with different temperature conditions. The requirements of plants for different nutrients may be affected by conditions of light, temperature and water supply, and by other factors of the general environment. Thus, the need for nitrogen may be less under conditions of relatively low light intensity whereas the need for potash in these circumstances may be greater, these facts being of importance in growing tomatoes under glass. The effect of nitrogen in relation to light may be shown by growing a plant under normal light conditions with insufficient nitrogen, when the leaves will show the well known 28

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symptoms of nitrogen deficiency - pale green, yellow, orange and red tints. If such a plant were then shaded, the leaves will turn a darker green and growth may be visibly increased. It can be shown that the lowered light conditions result in an increase of solubility, a breaking down of proteins, thereby rendering the nitrogen of these available for growth processes. Iron and zinc deficiency symptoms may be less severe under conditions of low light intensity, whilst boron deficiency effects are less severe and magnesium deficiency effects are more pronounced in wet seasons than in dry ones. The raw materials needed for plant growth consist of carbon dioxide, which is obtained from the atmosphere through the stomata of the leaves, water and the so-called mineral nutrients, which normally enter the plant through the medium of the roots. The importance of water and carbon dioxide in the nutrition of plants is apparent, as water often comprises 80 to 90 per cent of the total weight of growing plants. Carbon and oxygen together may account for over 80 per cent of their dry matter, the solid matter remaining after water is removed. The mineral nutrients, measured by the ash content of the plants, often contribute from five to 15 per cent of the dry matter. (The mineral residue is obtained when the organic matter is destroyed by heat). It has been shown in recent years that certain organic compounds, known as growth promoting substances or hormones, are capable of producing marked growth responses such as increased root growth, shoot and leaf curvatures, stimulation


"Carbon and oxygen together may account for over 80 per cent of plant's dry matter, the solid matter remaining after water is removed." or suppression of sprouts, increased fruit setting and prevention of fruit abscission. These growth responses occur in plants, and some are also present in soils and natural manures. They appear to perform important functions in the growth of plants. Examples of substances of this kind which can produce growth responses are 13 indole-acetic acid, 13 indole-butyric acid, phenyl acetic acid, A, naphthalene-acetamide, vitamin B1. At present, it is not clear to what extent growth substances are absorbed by plants from soils, although it has been shown that vitamin B1, which occurs naturally in soils, can be obtained in this way. This was an aperitif and we hope it will serve to let you get to better know your plants. It’s only then that you will get the best MY from them.

For an archived list of Luis Bartolo’s previous articles visit www.maximumyield.com

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"When a garden becomes infected with harmful spores or insects, time-consuming extremities are required to revive optimal homeostasis."

Cleanliness is Next to

Godliness by Lee McCall

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MAXIMUM YIELD Australia - November/December 2009

Constructing an efficient indoor garden to work accordingly with the fluctuations of the outdoor climate can be initially labour intensive. Attentiveness and prior research is required in order to implement the correct equipment to create a successful garden. For optimal operation, containment and isolation is essential to any custom layout or design. Also depending on the area, weather demographics will determine the need for certain heating and cooling. If and when there is an imbalance in the environment of a garden due to external factors, the risk of detriments increases and production is affected. Even with ideal equipment and design, hobbyists and commercialists may experience a variety of dilemmas if the growing area is not maintained and cleaned regularly. Aside from inevitable dead leaves, cleanliness of a garden should not centre on only removing physical debris and trash from the area. Of course the piling up of dead plant matter is never wise to ignore or make habit of; focus on aspects of the garden that are penetrable from outside sources. Intake points for fresh air exchange should always be filtered in some form or fashion, even if the provided source is another area not from outside. Many different gardens fall victim to a menu of damages resulting from fungus and insects acquired through untreated


air from the outside world. When a garden becomes infected with harmful spores or insects, time-consuming extremities are required to revive optimal homeostasis. In conjunction with proper sanitation practices, this is when the extra time spent studying pre-design and layout before hand assists greatly. Healthy plants resulting from healthy environments, increases the resistance to insects and disease. Poor airflow and high humidity levels can fuel insect and fungal reproduction. In my experience, spidermites and powdery mildew infections are the most common flaw that many simply cannot rid their crops of once transmitted. Battling spidermites and other plant pests is a good indication that a garden was not up to peak performance in one way or another. Treatments to reduce insect populations may prove to be very expensive in ways of time and money depending on severity of the issue. Health and vigour will definitely show through rate of production and yield, on how bad a garden was affected. Either way, hindrance is almost guaranteed amongst the garden. Consumables require post-treatment to rinse produce of residual counteractants. Do not use systemic treatments on consumable crops unless hazards are known and products are certified food-grade safe. Foliar applications are the most common form of treatment since the majority of plant attacking insects feed upon the leaf tissue itself. Action must take place when lights are off as this is when plants are in their downtime of production. Foliar spraying when lights are on increases the chance of burning foliage. Consistent

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Cleanliness is Next to Godliness

"One microscopic spore is capable of recreating an entire colony of mould." applications are recommended to maximize the effectiveness of whichever active ingredient is chosen for utilization. Every three days an infested garden should receive regular treatments to disrupt breeding cycles amongst plant pests. Once a problem is considered controlled, apply one to three more applications for insurance purposes, to prevent re-infestation. The majority of many crop infesting insects are apt to develop immunities to those who insist on using the same treatments over and over again. Always change up pesticide regiments by active ingredient to minimize resistance and tolerance build-up. If plants are in their beginning stages of life when a bug problem occurs, anywhere from clone to mature vegetative growth, submersing the entirety of the plant structure apart from for the root mass is optimal. This method allows complete uniform coverage of all possible contact points where bugs are possibly present and feeding. It also aids in rinsing away a vast amount of viable eggs that are attached to the plant in many areas inaccessible to foliar penetration, such as the under sides of leaves. Upon selecting the proper foliar treatments for your garden, always consider a wetting agent to incorporate with the spray. Wetting agents, also known as surfactants, help to emulsify the many oil-based control products into the water of which it is diluted. Along with using tepid to luke-warm temperature water for oil-based applications, the surfactant will allow the spray to maximize coverage 32

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of surface area on the leaf, rather than bead up and roll off the exterior. Vitality boosters like seaweed or kelp complexes, B-vitamins and silica supplements are great additions to blend with your choice of foliar treatment. Along with the insecticidal effects of the pesticide, the other additions promote healthy metabolism and immunity function to maintain productivity and overcome the stress of insect attacks. Indifferent from bug attacks, but considered just as detrimental, fungal problems can appear out of nowhere. This can be extremely frustrating to any grower due to the fact initial discovery of certain moulds or fungus usually means it has been present in abundance for a while without identification. Powdery Mildew, an extremely common form of a nuisance fungal attack, will seek refuge in any high humidity, low airflow situation. Destroying many fruit and flower bearing plants after much hard work has been spent creating it, this mould is extremely hard to rid gardens of. Patches of this fungus appear on foliage and fruits causing undesirable aromas, flavours and physical appeal. Roses and squash are particularly favoured by these reproductive spores, and once infected steps similar to that of a pesticide regiment should put into effect to combat the fungus. Neem oil complexes provide both properties of anti-fungal and natural pesticide all in one bottle; other companies have synthesized bacterial solutions that counteract the fungal production on the tissue surface itself. Whole milk actually serves as one of the best household remedies that give impressive results upon application. For foliar or submersible treatments, dilute one tablespoon of fresh whole milk into a quart of high quality, preferably distilled water. This easy solution serves as an effective cheap treatment, but should never be over applied. Sulphur-based products are equally effective as anything else, but they carry over the staining smell of sulphur to your garden. For larger, mature gardens that are unable to receive steady foliar treatments, sulphur vaporizers, also known as sulphur burners, provide immediate coverage to all possible points of a garden if given the proper dispersion time. Flooding the infected area with sulphur fumes, the mildew refuses to co-exist in the same atmosphere where sulphur is present, and can easily be knocked out of commission. The problem gardeners have with combating mildew production is that one microscopic spore is capable of recreating an entire colony of mould. Airborne, these spores will multiply through gardens covering walls, equipment and anything in contact with the grow room. Thorough sterilization is imperative if mildew occupies more than half of the garden. Ozone generators are known for sterilization purposes, but have never made a vast impact for me when used to combat powdery mildew. Train yourself to possess clean habits and practices when in and around your garden. Transferring equipment or plants from


Two spotted spidermites.

one grower’s garden to your own without pre-treatment for these natural atrocities is a guaranteed window for spreading these plant-transmitted infections. Heavy foliar feeding can leave residual build up on walls, floors and equipment, so maintain a steady routine of cleaning these areas with peroxide, alcohol or bleach solutions. Utilize protective coverings to the original floor and walls, such as plastic tarp or poly to protect from staining or permanent damage. Protect gardens from open crawl spaces or areas exposed to outside contaminants. Shop vacuums that boast wet and dry properties are handy for accidental spills and dead leaf removal. Practice the art of cleanliness to ensure a garden next to godliness. MY

The top 10 ways to keep the grow room clean and plants happy can be found at www.maximumyield.com

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Not Convinced?

Why Water Quality is Essential to Plant Health by Trevor Holt

When choosing an appropriate site for a hydroponic set-up we sometimes overlook the quality of the water which supplies the site. The way you water your plants and the amount of water you give them can be a major factor in the overall health of the plant.You have to ask the question, "How clean is the water?� Most town water should be suitable for plant growth, however, I would advise you to invest in a water purification system, not only for the plant's benefit but also your own! It is my view that you just don't know what your suppliers are throwing in the water to make it safe to drink. A few years ago we experienced a Cryptosporidium and Giardia outbreak in Sydney. As well as people getting sick, there was a major rush of growers experiencing root zone problems. No matter what they did the problem continued to haunt them. Initially, they blamed everything from the nutrient they were using to propagation gels, additives and the advice they received. As each case was investigated they found that even though all systems, lighting, airflow, growing methods and nutrients used were very diverse, all growers had the same problem. Naturally a common denominator was researched – and it was, of course, water. Some growers were hard to convince, considering they were on 'town supply' and, therefore, the over-riding belief was the water quality must be of a high standard (if it's safe to drink it must be okay for my plants). Not so. Did you know that over 50 different chemicals can be legally added to our town water supply in order to make it safer to drink without us even knowing? Listed below are just a few of the major ones which can also affect your plants: Calcium Oxide or hydroxide, potassium aluminium sulphate, liquefied chlorine, sodium silicofluoride slurry, sodium hypochlorite solution, fluorosilicic acid and various other 36

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electrolytes. This is not taking into account the number of chemicals that are added to our water supplies unintentionally. Most of our catchment areas are exposed to the elements, some of which may include lead, copper, pesticides, herbicides, asbestos and raw sewerage to name a few. I've seen plants that look absolutely amazing when small and as soon as they are exposed to the main system, they crash. Why? Poor water quality. Even if you are drawing your water from bores or rainwater off the roof, you still run the risk of not only collecting water, but a high mineral load, which when fed to your plants can affect the nutrient levels, potentially giving your crop toxic shock. Rusty, galvanised or copper pipes also contribute to higher levels of heavy metals such as zinc (zincalume) and iron in the solution. If these metals are present in any quantity, your plant will experience toxicity symptoms even if you are using a balanced full spectrum nutrient. A good way to check if your water is suitable is via a digital salt meter (nutrient tester). If you get a reading in water above one conductivity factor (CF) you would be wise


to consider a water purifier of some sort. The purer the water and the more neutral the pH in your water supply, the better. Before I continue, I have to tell you that out of all the growers who were experiencing root zone problems, only one continued having problems (eventually driving the client to abandon hydroponics) because he was the only one who didn't buy a water purifier. For a small investment of around $200, he lost a fortune, (think about that!) Over-watering is a common problem with novice and experienced growers alike. Commonly known as 'killing plants with kindness', most growers assume that the plant will take as much water as you can throw at it. This is another fallacy. If the water you are supplying to the plant does not have the right oxygen, nutrient, pH and water mix, the plants can actually drown in a saturated mess. Oxygen is unable to get to the plant and consequently they start to suffer, developing deficiency symptoms. Brown, blotchy leaves turn down and start to wilt. The grower panics and throws more water and nutrient in the system, unwittingly overdosing their beloved plants; end result...the plant dies. If you experience this, you need to drain off the media completely.You can gradually bring the plant back to good health by feeding it oxygen-rich pure water. Good drainage is essential to the recovery process; therefore, consider the media (substrate) you are using. If you are doing everything right, new growth should start to appear in approximately two weeks. Plants generally take about that long to recover from a stress situation. Under-watering produces very similar symptoms; however, they can occur more quickly with more dramatic consequences. It can be a scary sight to check your garden and find your entire crop has suddenly wilted overnight. The problem is a result of one thing: lack of water. Check that your water pump is working and is clear of any root matter or fine media particles. Take the pump apart and clean it thoroughly. If this is the problem, it is easy to rectify and the plants should recover

Commonly known as 'killing plants with kindness', most growers assume that the plant will take as much water as you can throw at it. If the water you are supplying to the plant does not have the right oxygen, nutrient, pH and water mix, the plants can actually drown in a saturated mess.

with no noticeable damage within a couple of hours. Once the watering cycle resumes, hourly checks to mark the recovery progress would be adhered to. Regular maintenance of everything that services the growing environment is essential, which will ultimately lead to a successful end result. Try to visit your greenhouse or grow room once a day to avoid any of the above mentioned catastrophes, especially during the flowering stage. Think of it this way: "A little maintenance a day keeps the problems away," and you'll get to reap the benefits at harvest time. Oxygenation’s Role in Healthy Water Oxygen keeps a plant's root zone healthy and allows the uptake of nutrients. Oxygen is the key to a high growth rate. Without oxygen around the roots, the root cells would die leading to root rot (pythium) problems and the eventual death of the plant. You cannot grow in water unless you have dissolved oxygen in it, so a well oxygenated nutrient solution is essential for a healthy root zone. The fine root hairs take up the nutrients and oxygen, and obviously the more root development, the more nutrients the plant can take up, hence a healthier plant and better yields! If you have still and stagnant water you're asking for trouble because that will cause root death due to oxygen depletion, which in turn could cause pythium (a fungal disease) to run rampant, or even attract harmful bugs like the sciarid fly (fungus gnats). Recirculating systems add that essential element to hydroponics: oxygen. When oxygen increases, so does growth, and in many ways it is more important to consider than nutrients. Root zone temperature also plays a very important part in overall tank control, and the ability for plants to take up oxygen, water and nutrient. The ideal root zone temperature is between 20 and 24°C. If the temperature falls below 20°C plant growth will begin to slow, and if it reaches 14°C, plant growth will stop altogether. On the other hand if the root zone temperature rises above 24°C the need for oxygen by the plant increases as the dissolved oxygen that is in the tank decreases. This can have a devastating effect on the plant and can accelerate outbreaks of pythium spores and other root zone diseases. My golden rule of oxygen - plants cannot take up their nutrients unless oxygen is present. The more oxygen, the faster the uptake of nutrient... but watch the temperature too! MY MAXIMUM YIELD Australia - November/December 2009

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Water Clean and Pure