http://www.articletrader.com/ Articles at ArticleTrader en-us http://www.articletrader.com/home-and-family/gardening/biological-pest-control.html http://www.articletrader.com/home-and-family/gardening/biological-pest-control.html Wed, 05 Dec 2007 00:00:00 -0600 Pesticide Use & Environmental Impact

Thanks to the increasing awareness about environmental issues, groups and individuals have started taking various initiatives to promote more sustainable life styles. Because of the adverse impact they have on the environment, “hard” pesticides are now being gradually sought to be phased out to make way for more environmentally friendly alternatives, “soft pesticides”.


But pest control, through pesticide use, is often necessary considering the fact that without a measure of control many insects can cause huge damage to crops. Besides,
insects can also affect our quality of life in many different ways. These pests, if not effectively controlled would pose grave public health risks and also create significant negative impacts to the economy. The use of pesticides, as a measure to ensure favorable outcomes, in areas related to food production, public health etc. therefore cannot be discounted.


Pest Control in Hydroponics

In hydroponic cultivation pesticide use is discouraged and often not required. This is because hydroponic crops tend to be more healthy and pest resistant as they are grown under controlled conditions under a precisely regulated nutrient regime. Hydroponics systems mostly use natural preventative measures to control pest and parasite infestations. One of these is companion planting which uses a clever strategy to repel pests by growing plants that produce smells disagreeable to the pests. These plants are grown along with the main crop which is intended to be protected.


But not all bugs are put off by the smell, and at times, other means have to be adopted such as biological insect control. Biological insect control uses predator insects to reduce or destroy infestations. The predator insects consume the harmful, crop damaging species and die out or leave the garden. This is a safe, poison free natural method of pest control. Predator insects are bred commercially for such use and have proved extremely beneficial in pest control. These mostly carnivorous insects do not attack vegetation and being extremely voracious consume bugs on a massive scale daily.


Infestation Control

The best way to keep tabs on infestation, whether in the greenhouse or the grow-room is to carry out physical inspections to check for any pests. This should be done carefully by checking all likely places where pests may be present like leaves, around stems and even the growing medium. If any bugs are detected the next step is to determine the type of insect and the number of plants affected. The strategy to eliminate the pests will depend on the number of bugs and the extent of the infestation.


Proper identification of the type of pest is important as this will determine which predator insect will best get rid of infestation. This can be done with the help of good garden microscopes and standard gardening reference books. Once an infestation is detected and the harmful bug identified, quick release of predatory insects to control the infestation should follow.


It should be noted that the environment has to be maintained to be favorable to the predator insects. Many predatory insects are susceptible to high temperatures; also there should also be an adequate source of water or shelter. The grow room environment will therefore need to be carefully monitored.


Common Predators

The following are some of the predators most commonly used:

Ladybugs (Hippodamia convergens)

Ladybugs are most effective against aphids. Ladybugs need plenty of water, so place a small dish of water in your garden. This will help keep both the ladybugs and the insects close to your plants. Adult ladybugs are orange and black and feed on aphids, mites, scales, thrips, whiteflies and beneficial insect food.


Aphidius Colemani & A. Matricariae (Aphidius colemani & A. matricariae)

These are small black wasp (2-3 mm.) with narrow waist. They have long antennae. They prey on aphids turning them into brown, mummified shells. These predators are most active at temperatures between 18-26C (65-80F).


Praying Mantis (Tenodera aridifolia sinensis)

These are large green or brown insects having fine papery wings. They are shipped as egg cases that take 2-8 weeks to hatch. These general predators prey on aphids, beetles, caterpillars, leafhoppers, hornworms, squash bugs, white flies and several other pests.


Lacewings (Chrysoperla carnea, C. comanche & C. rufilabris)

These are general predators that feast on mealybugs, scales, spider mites, thrips, white flies and insect eggs. They are green or brown in color when adults. Lacewings are most active in temperatures 24-28C (75-80F).


Phytoseiulus Persimilis, New Zealand – (Phytoseiulus persimilis)- New Zealand Strain

These are bright orange mites (0.5 mm./1/20 in.), and are very effective against spider mites. They breed twice as fast as spider mite to make short work of any spider mite infestation. They do not form webs, but move along the plant using webbing to catch spider mite. These predatory insects are most active in temperature ranges 22-35C (72-100F) and 60-80% humidity.

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Diana
Writes about indoor gardening.

Source: http://www.articletrader.com ]]> http://www.articletrader.com/home-and-family/gardening/the-importance-of-chelates-in-plant-nutrition.html http://www.articletrader.com/home-and-family/gardening/the-importance-of-chelates-in-plant-nutrition.html Thu, 22 Nov 2007 00:00:00 -0600 Chelates are compounds that serve to make a number of nutrients, especially micro-nutrients available to plants. In the absence of chelates in the nutrient solution, plants would be deprived of key micro-nutrients which may lead to deficiencies, inhibited growth and several other undesirable conditions. Growers should therefore, ensure that these compounds are present in the nutrients they use in hydroponics cultivation.



The word chelate is derived from the Greek word “chele” which means “claw”, a rather apt association because chelation is a process somewhat like grasping and holding something with a claw. It would therefore be interesting to see how chelates facilitate absorbtion of nutrients that would otherwise be unavailable to plants. Many trace elements carry a positive charge as ions in solution, while the pores or openings on the roots and leaves of plants are negatively charged. The element is therefore unable to enter the plant because of the fixation of the positive and negative charges. However, with the addition of a chelate, elements such as iron are encapsulated and the positive charge changes into a net negative or neutral charge, which allows the element to pass through the pore into the plant.



Synthetic Chelating Agents

Most commercial fertilizers include one or more chelating agent and higher quality fertilizers incorporate several of these agents. The chelating agent in the fertilizer is identified on the label beside the trace element it serves to make available to plants. If the label on the pack has the letters EDTA beside some trace element, the fertilizer contains Ethylenediaminetetraacetate the most commonly used chelating agent. Higher quality grades of fertilizers also contain DTPA or Diethylenetriaminepentaacetate. Fertilizers that include ethylenediaminedihydroxy-phenylaceticacid, denoted as “EDDHA” beside iron on the label are the highest quality fertilizers.



Chelates have several points of attachment with which they “grasp” the trace element. EDTA has four connecting points to the elements it chelates, while DTPA has five, but the higher number of connection points may not always be an advantage. In some cases the four connection points may hold the element too tightly, while in a different situation these may not hold it tight enough.



When they require the chelated element, plants remove the element, for example iron, from the chelate and it is absorbed into the plant. However, being foreign to the plant, the chelate itself is not absorbed and is released back into solution.



The effectiveness of a chelating agent depends also depends the pH of the solution. EDTA is best suited to slightly lower than neutral pH levels while DTPA is most effective at high pH values. DTPA is more costly than EDTA and less soluble and is found in higher quality fertilizers.



The most effective of the synthetic chelating agents is ethylenediaminedihydroxy-phenylaceticacid (EDDHA). It is found only in select fertilization formulations because of its relatively high cost. It has been demonstrated that plants perform better, even under adverse conditions when the primary source of iron is chelated by EDDHA. In experiments on aeroponically grown chrysanthemums a portion of the plants were inoculated (infected) with a root disease (pythium). Only four percent of the plants that were supplied with EDDHA developed chlorosis (yellowing of leaves), while 35 % of plants supplied with DTPA became chlorotic. Of those supplied with HEDTA, 18% became chlorotic. Additionally, it was found that EDDHA supplied plants absorbed twice the amounts of zinc than plants supplied with HEDTA and DTPA.



Biological Chelating Agents

Apart from the synthetic chelating agents, there are compounds that occur naturally like fulvic acid that function as “natural” chelating agents. Plants growing naturally depend on fulvic acid and other chelating agents found in nature to enable absorption of trace elements. Fulvic acid results from the decomposition of organic matter into humus. The humus is acted upon by microbes to produce humic acids. The humic acids are further processed by micro-organisms into fulvic acids. Like some synthetic chelating agents, Fulvic acid forms four-point bonds with the elements it chelates, but unlike the synthetic agents it can be absorbed into the plant. This adds to the mobility of the nutrients within the plant. The nutrients chelated by fulvic acid can move more freely which prevents a number conditions like localized calcium deficiency which happen due to low mobility of nutrients.


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Fulvic acids can be most effective when the growing environment in the root zone (rhizosphere) is above or below optimal. Unlike synthetic chelating agents fulvic acid retains its effectiveness under conditions like high or low pH. Under such adverse conditions plants supplied with fulvic acid have been found to be remarkably free of signs of stress, deficiency etc. than plants supplied with synthetic chelating agents. Fulvic acid also produces all round improvement of transportability of various nutrients in plant tissue. This is not limited to the fertilizer minerals but also helps improve the transport of other plant fluids.



Amino acids form another category of biological chelating agents. Amino acids can function well as chelating agents due their positive and negative charges that can act as north pole and south pole of a magnet. As chelating agents amino acids form five point bonds with the mineral element.



Conclusion

As chelating agents enable absorption of a variety of nutrients vital for healthy plant growth, growers should look for nutrients that offer a range of chelating compounds. This will ensure nutrient availability over a wide range of conditions, including those above or below optimal.




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Source: http://www.articletrader.com ]]> http://www.articletrader.com/home-and-family/gardening/foliar-fertilization-in-hydroponics.html http://www.articletrader.com/home-and-family/gardening/foliar-fertilization-in-hydroponics.html Thu, 15 Nov 2007 00:00:00 -0600 nutrient. solution to the plant root. This is an effective method in most cases, but under certain conditions it may be quite ineffective. Though plant root systems can efficiently absorb the nutrients in normal circumstances, under conditions of root damage, nutrition deficiency or propagation from cuttings alternative strategies may need to be adopted. Foliar feeding, a technique of providing nutrients through the foliage of plants is often resorted to under such circumstances. Foliar feeding enables plants to absorb nutrients through the leaves. The minerals within the nutrients can then be translocated by plant within its tissues.


Nutrient Uptake in Hydroponics

Nutrient uptake, in hydroponics is a complex process that may be adversely affected by factors such as nutrient interactions, nutrient depletion, element unavailability due to the element being “bound” etc. Even environmental conditions like temperature can affect nutrient uptake through the roots. Plant pathogens such as fusarium pythium and phytophthora can also affect the normal functioning of the root zone severely restricting nutrient uptake. Other plant stress conditions such as anaerobic conditions in the root zone where oxygen is deficient, can limit nutrient uptake. Many other conditions can cause stress to plants such as humidity, lack of light, high radiation levels, etc. and directly or indirectly affect nutrient uptake. Under such situations foliar feeding has been found to be most effective in ensuring reliable nutrient uptake for healthy plant growth.
Foliar fertilization can thus help protect crop yields and quality against the vagaries of a wide variety of agents that can cause crop damage including climate, pests etc.


Foliar absorption

Absorption of nutrients in foliar feeding takes place through stomata on the leaves. These are located on the underside or on both sides of the leaf. The stomata normally function to enable gas exchange for photosynthesis and releasing water vapor in stomatal transpiration. But the leaf can also work as an organ for absorption and excretion of water and substances dissolved in it. Foliar feeding takes advantage of this to supply vital nutrients through the stomata. However, it is not possible for plants to be fed solely via the leaves; therefore the scope of foliar fertilization is limited. It is however, extremely effective as method of supplying micro nutrients.


There are several aspects of foliar fertilization that are not yet fully understood. There are several known and unknown factors that influence the effectiveness of foliar fertilization. It is known however, that the rate at which the nutrients supplied by the nutrient sprays are absorbed by the leaves and translocated within the plant is of critical importance. Also, practical experience provides several pointers for utilization of the technique for optimal benefit.


Application Considerations

The use of a good quality, non ionic wetting or sticking agents, such as Coco Wet, is vital to enable droplets to adhere to leaves. They also assist in the absorption of the fertilizer solution into the plant tissue. The foliar fertilizer solution is best applied as a fine mist until 'run off' so that the entire leaf surface is wetted. The effectiveness is also dependent on the timing of the application during the day. Early morning and evening are best suited as the conditions during these times of the day are ideal to allow the leaf to dry rather than stay wet for a long time. Foliar solutions are best applied while there is light but when temperatures are still cool; they should not be applied in hot, sunny conditions. In hot, sunny conditions the stomata are likely to be closed making the feeding ineffective. For the same reasons feeding is ineffective when the plants are wilting or under osmotic stress.


For the best results foliar feeding should be carried out on a regular, weekly basis. It is also found to be particular beneficial when limited to times of high nutrient demand. It is during stages of active growth such as during fruiting that foliar feeding is known to yield optimal results as during these stages leaves are particular efficient in absorbing nutrients.


Application in Hydroponics Cultivation

Even when hydroponic crops may appear to be well supplied with the necessary nutrients, it has been shown that they can still benefit from application of foliar fertilizers. Foliar fertilization was found in a number of studies involving hydroponically grown crops such as capsicum and potato, to dramatically increase yields. A weekly foliar feed applied to tomato crops grown in rockwool, also produced substantial improvements in both quality and quantitiy of the yields. It is believed that similar results can be obtained with a number of hydroponic crops with similar nutrient requirements. According to experts in the field, the process of foliar fertilization, is likely to emerge as a growth enhancing cultivation technique in the near future rather than just a 'quick fix' solution for mineral deficiency symptoms.



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Source: http://www.articletrader.com ]]> http://www.articletrader.com/home-and-family/gardening/lighting-and-reflectors-in-hydroponics-cultivation.html http://www.articletrader.com/home-and-family/gardening/lighting-and-reflectors-in-hydroponics-cultivation.html Wed, 31 Oct 2007 00:00:00 -0500 Lighting technology has come a long way since the times of the incandescent lamp and with several different types of lamps now available choosing the right lamp to suit your indoor gardening needs can, at times be confusing. There are other accessories to consider too like starters, timers, wiring etc. which can further confound the uninitiated. But while considering all the paraphernalia, growers sometimes tend to neglect one extremely important aspect of the lighting systems – reflectors.


Importance of Reflectors

To get the best from their lighting system growers would do well to understand how reflectors work and how reflector design has evolved over the years with advances in lighting technology. Reflectors perform the very important function of gathering the light emitted by the lamp and then directing it as required. Therefore, even though you may use the best lamps in the market, if you don’t use the right reflector most of the light produced by the lamp might be wasted. However, “tall crop” growers need not be concerned as their crops can soak up all the light they need from just bare lamps hanging down among the plants. “Short crop” (plants under one meter tall) growers, need to carefully consider available reflector designs to choose the one best suited to their needs.


Reflectors come in different designs and not all designs have comparable efficiencies. Some reflectors are many times as efficient as others thanks to the technical improvements in reflector design and manufacturing. One of the problems in the past was rooted in the misunderstanding of how H.I.D. (High Intensity Discharge) lamps produce light. HID lamps give their strongest light from the sides of the lamps, quite unlike the typical incandescent bulb. Vertical mount reflectors, which were the first reflectors developed for HID lamps proved highly inefficient with only about 9% of the light reflected to the plants. The rest of the light output was completely wasted in illuminating the grow room walls.


Developments in Reflector Design

Lighting efficiency increased dramatically with the introduction of the horizontal reflector. The sideways orientation of the lamp also increased the direct light to the crop as also the horizontal reflector which bounced more light to the crop. This arrangement seemed fine for some time until the lamps started burning out after only a few months.
Also there was always the possibility of electrical shorts in the socket wiring associated with this design. The reflector design then underwent major modifications with more open designs, incorporating vents, ducting even small exhaust fans. With the basic design features incorporated the attention turned toward the finding the material that would reflect light most efficiently. The specifications called for a surface that would reflect the light and also distribute it evenly onto the crop without localized heating and shadowing. Several years of research led to the development of a flat white surface that – coated with Titanium Oxide –fitted the bill to a T. It reflected 20% more light than the best glossy white finish. It also did not produce the uneven glare that the most reflective of glossy surfaces produce. With a unique method of applying Titanium coating the surface reflectivity touched 95%, i.e. the surface was able to reflect 95% of the light incident on it to the crops. This reflected light in addition to the direct light from the lamp, boosted the overall lighting efficiency in the garden to near perfect levels.


Benefits of Improved Design

Growers were quick to realize that these new reflectors offered an important benefit – they were no longer constrained to locate their growing systems in inaccessible locations. With the old style reflectors that allowed most of the light to fall on the walls growers tried to redirect some of this wasted light by covering the walls with Mylar or other reflective materials. But this resulted in gardens being moved into corners to take advantage of the reflective wall coverings creating problems with poor air movement, heat build up and inaccessible plants. All that changed with the new reflectors- light was now directed onto the garden, no light wastage on the walls meant no need for reflective walls and no need to locate the grow area in cramped spaces.


Accessible locations for the gardens improved air movement eliminated the problem of heat build-ups and promoted more growth friendly conditions in the garden. A free-standing garden with easy, unhindered could now allow easy access for inspection and carrying out other chores that help plant growth. It also discourages unwanted intruders like pests and bugs.



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Source: http://www.articletrader.com ]]> http://www.articletrader.com/home-and-family/gardening/pest-control.html http://www.articletrader.com/home-and-family/gardening/pest-control.html Mon, 22 Oct 2007 00:00:00 -0500 grow rooms would seem to provide ideal protection to plants against pests and parasites that can cause much harm to crops grown conventionally. It would seem reasonable to believe that since plants are grown in a comparatively sanitized environment without soil, a pest attack scenario would be unlikely, even remote. But pests wouldn’t be pests if they were so easy to shake off; so whether it is a hydoponics grow room or a green house, these tiny and not so tiny marauders have to be kept away. Fortunately, there are several ways growers can go about protecting their precious plants against these invaders.
Anything and everything can serve to introduce pests into the grow room, even humans are no exception. Once pests gain a foothold in the grow room, they multiply manifold, rapidly consuming plants and playing havoc with your indoor garden. The first step to regain control over your grow room is to identify the culprit. Once this is done a number of “soft” and “hard” control options are available to target the offending intruders.
Control Strategies
When only a few plants are infested growers can dip a small brush in insecticide or methylated spirits and apply directly onto plants to eradicate pests such as mealy bug or scale. This method is often very effective in protecting valuable indoor plants where spraying may not be acceptable. Moths can be dealt with using pheromone traps that help eliminate adult moths before they can lay eggs. Even hand-held vacuum cleaners have been reported to be effective against flying pests, particularly whiteflies.
Repellent Sprays, Powders and Formulations
Garlic sprays and hot pepper wax barrier are often used by growers in pest control. While these are mostly available off the shelf at any gardening supplies store, many growers prefer to make their own versions. However, the results seem to be mostly inconsistent, with some growers claiming excellent results while others reporting less than satisfactory outcomes. Some growers report that pests thrive on foliage treated with repellents.
Soaps and Oil Sprays
Soaps and oils have also proved effective in pest control. They work by blocking the pest’s breathing pores, thus smothering the pest. They also prevent some pests like mites from moving around and breeding. Soaps and oils are fairly safe. They can be easily stored and conveniently applied. Regular application over long periods, however, leads to buildup of oil/soap on hydroponic system components. This can be washed off from time to time.
Certain mineral compounds and diatomaceous earth work as natural or non-chemical insecticides. Diatomaceous earth has desiccant action on the insects. It also forms an abrasive layer slowing crawling insects like slugs and worms. It forms a dusty residue on hydroponic fruits or vegetables must be washed off.
Biological Formulations
A number of bio-pesticides are available in the market today. Perhaps, the most widely used of these is Bt spray, which is obtained from the bacterium Bacillus thuringinesis. Bt spray is applied to plants which is then absorbed by caterpillars as they feed. A bacterial toxin is formed in the digestive system of the caterpillar, which causes it to stop feeding. Dehydration sets in and the pest dies in a few days. Different strains of Bt have been developed for use against specific insects. It is important to use the right strain of Bt meant for a specific pest as the wrong strain will not work.
Some other products have been formulated from fungal pathogens of various insects. These work best under the right conditions. If the conditions, for example, humidity is not high enough, the controls are not effective.
Botanical Formulations
The two most common botanical extracts used for pest control in hydroponics are a pyrethrum, derived from a daisy (Chrysantehmum Cinaeraefolium) and neem oil derived from the seed kernels of the Indian neem tree (Azadiracta indica).
Pyrethrum is often combined with other compounds to enhance effectiveness; it can be used to control a wide range of pests. Neem oil or various extracts of neem are available as oil, solvent extract and as a ground product. Neem is an insect growth regulator, meaning, it stops the insect's life cycle. Neem is effective on particularly difficult pests like whitefly; it is also a good general purpose spray option for small-scale growers.
Growers often erroneously assume that since they are made with plant extracts soft pesticides are safer than chemical pesticides. The truth is that these can be more toxic to humans than some synthetic pesticides. Handling these products requires the same care and application as synthetic biological controls.


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Source: http://www.articletrader.com ]]> http://www.articletrader.com/home-and-family/gardening/busting-grow-room-odors-with-activated-carbon.html http://www.articletrader.com/home-and-family/gardening/busting-grow-room-odors-with-activated-carbon.html Mon, 15 Oct 2007 00:00:00 -0500 Versatile Cleaning Action
Activated carbon, with its phenomenal absorbent capacity has long been in use as a purifying agent for air and water. Its action in removing gases, particulate matter and even micro-organisms has found many applications in diverse fields from gas masks for use in wars to absorption of radioactive gases in nuclear plants. Activated carbon filters have also proved very effective in controlling odors from grow rooms and green houses.
Activated Carbon in Hydroponics
Commercial activated carbon usually comes in the form of pellets; these have millions of tiny pores on the surface. These sub-microscopic pores form an extensive network that effectively increases the area of the absorptive surface manifold. Activated carbon works by acting as a very efficient sponge, trapping within its pores all kinds of impurities, gaseous as well as particulate. The smaller pellets have been shown to be especially effective in trapping malodorous contaminants as they leave little space for air to escape through.
Activated carbon is safe and 100% non toxic, therefore it can be used in grow rooms where the cleansed air can be re-circulated. The best results with carbon filters are obtained with these are used in conjunction with an exhaust system, which cleans the air as it leaves the grow room. With this method all stale air gets exhausted and fresh oxygenated, C02 rich air is continually introduced into the grow room.
The typical activated carbon filtering set up comprises an exhaust fan drawing air through the charcoal activated carbon filter. The air is first passed through a poly pre-filter cover that is designed to trap larger particles before it reaches the carbon pellets. When the air passes to the carbon pellets, the odor molecule is scrubbed and drawn out through the exhaust system. The activated carbon air filter and exhaust system should be installed at the highest level in the grow room because warm, odor laden air tends to rise.
Humidity and Temperature Considerations
High temperatures and humidity adversely affect on the filtration capacity of activated carbon. It becomes important, therefore to adjust air flow into the filter with temperature fluctuations for effective functioning of the filter. One simple control method makes use of a thermostat to adjust the air flow with temperature variations. Besides temperature variations, extremely high levels of relative humidity also lead to diminishing absorption capacity. A relative humidity of 60%, it has been observed, is the upper limit beyond which filtering performance drops sharply. The relative humidity should therefore not be allowed to exceed this limit.
Optimizing Air Flow with Ducting
The flow of air inside a grow room is of key importance, especially in an all plastic inside wall environment that is now becoming increasingly popular. Such grow cabinets and grow rooms like Hydrohut tend to give off a plastic smell due to organic deposits on the inside polyurethane walls. Wiping the inside of plastic sheet with paper towels and water removes the offensive deposits and effectively de-odorizes the environment in the grow room.
Other odors can be more persistent in such conditions and the best way to tackle these is to have proper ducting arrangements to ensure optimized air flow. As intake and exhaust vent holes are provided on the grow rooms providing proper ducting is not difficult. Fresh air from outside should be blown in with an adequately sized blower through a duct, through intake hole. Similarly, air to be exhausted should be forced out of the Hydrohut through a charcoal filter with an exhaust blower, through the exhaust vent hole. Fitting a charcoal filter inside the grow chamber will help remove harmful organic molecules. If there are multiple grow rooms in a room, a carbon filter should be placed inside each grow room to avoid air quality problems.
Not using ducting can lead to all types of problems. For instance, blowing in air and not providing a way out by not using ducting will result in the impure air passively finding its way out and then re-entering the grow room. Even in cooler conditions in ocean side towns it is advisable to use proper ducting to ensure intake of fresh air and venting of stale, odor laden air.
Ideal Filtering Solutions
Activated carbon filters offer ideal solutions to odor and air borne contaminate removal problems. They absorb impurities to the extent of about 20 to 40% of their own weight. Carbon filters also act against mold and bacterial contamination in greenhouses and grow rooms. There is no residual smell, besides; there is no additional electrical cost for the user associated with incorporating activated carbon filter in the exhaust system. With their 99 % aromatic absorption rate activated carbon filters ensure the removal of all odors from the air. Activated carbon filters are also available in environment friendly models that allow the user to refill or replace the carbon cartridge as necessary.


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Source: http://www.articletrader.com ]]> http://www.articletrader.com/home-and-family/gardening/factoring-in-ph-in-hydroponic-cultivation.html http://www.articletrader.com/home-and-family/gardening/factoring-in-ph-in-hydroponic-cultivation.html Mon, 08 Oct 2007 00:00:00 -0500

Macronutrients and Micronutrients


Plants need two types of nutrients, namely macronutrients and micronutrients. When grown outdoors, plants are able to obtain both macronutrients and micronutrients from the soil, but when grown indoors these have to be supplied in the right amounts. There are two types of macronutrients- primary macronutrients namely nitrogen, phosphorus and potassium which are required in large amounts, and secondary macronutrients – sulfur, calcium and magnesium that are required in smaller amounts. The micronutrients iron, manganese, zinc, copper, chlorine, boron and molybdenum are required in even smaller amounts, but are still essential for growth. Each of these macro and micronutrients serves specific purposes for the plants and can be absorbed only when the pH of the solution is conducive to the absorption process. If the pH levels are too high or too low some nutrients become available only at potentially toxic levels, while others simply become completely unavailable.



Understanding pH

pH levels are basically indicative of the acidity or alkalinity of a substance and range from 0 (acid) to 14 (base). A pH of 7 is considered neutral and one that best supports absorption of macro and micronutrients. But for all practical purposes, taking into account other factors like the differences between plants, it is generally accepted that for best results the pH of nutrients solutions should be between 5.5 and 6.8.


The pH scale is structured to represent acidity and alkalinity differentials by a factor of 10. For example, a solution with a pH of 5 is 10 times more acidic than a solution with a pH of 6. Similarly a solution with a pH of 4 is a hundred times more acidic than a solution with a pH of 6. The same applies to alkalinity, though in the reverse order. A solution with a pH of 9 is 10 times more alkaline than a solution with pH of 8.



Monitoring pH

It is known that plants will grow best when the pH of the nutrient solution is between 5.5 and 6.8; obviously therefore, frequent monitoring of pH levels makes sense and several simple methods are available to keep track and make necessary adjustments. Hand held pH meters featuring glass probes offer an easy way to track the pH of nutrient solutions.
These display the pH values on a digital readout when the probes are dipped in the nutrient solution. If the pH is high or low, this can be corrected using suitable pH Up or pH Down liquids. Some of the commonly used pH lowering solutions are nitric acid, phosphoric acid, citric acid and vinegar. Potassium hydroxide is used for raising the pH.


One source of problems that should be taken care of at the outset is the water that is used in the nutrient solution. Before using the water it is good practice take its pH reading and adjust it as needed. Also it is best to avoid using hot water when mixing hydroponics nutrient, because hot water pipes are prone to scaling, and the calcium from the scales can raise pH levels which can be difficult to lower. Finally, indoor growers using rock wool as growing medium need to take measures to offset the inherent alkalinity of the medium. One solution is to use nutrient formulations specifically designed for use with rockwool.



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Source: http://www.articletrader.com ]]> http://www.articletrader.com/home-and-family/gardening/plant-propagation-in-hydroponics.html http://www.articletrader.com/home-and-family/gardening/plant-propagation-in-hydroponics.html Thu, 27 Sep 2007 00:00:00 -0500 hydroponics. These are seed germination and rooting cuttings (cloning).


Rockwool is the most popular propagating medium and is used as blocks or in loose or granular form. Rockwool blocks are 1” cube in size with a hole ¼” deep at the centre. A flat of 98 such blocks fit into a standard tray. The rockwool blocks are soaked and pH balanced and one seed is placed in the hold. The seeds are then covered with a thin layer of Vermiculite or Perlite. The tray is then covered with a lid. When the seeds germinate the cubes are separated and placed into bigger growing cubes or other aggregate.


Though not used as extensively as blocks loose or granulated rockwool is also popular with hydroponics enthusiasts. Loose or granulated rockwool is taken in a standard plastic starting tray and the seeds are spread evenly on the medium. The seeds are then covered with a thin layer or rockwool or Perlite and the tray is then covered to prevent loss of moisture.


Cloning is a method of asexual propagation in which stem cuttings from a healthy plant are taken and then rooted. Most plants can be propagated using this method of asexual propagation. Cloning produces plants that are exact genetic duplicates of the original. These mature much faster which saves a lot of time. As oxygen is vital to the development of roots air pumps are often used to provide a steady supply of oxygen to the cuttings. Rockwool cubes, pH balanced with their flats soaked in a diluted, high phosphorus nutrient solution are widely used as propagation medium.


Using a clean, sharp blade, a small branch consisting of a growing tip with two or three leaves is cut. This clipping is then allowed to stand in water as the next clipping is cut. The procedure is repeated until the required number of clippings has been taken. A fresh cut is then made on each cutting just above the first cut. The clippings are then dipped in a rooting compound and inserted one inch deep into the rooting cube. The tray is then covered with a plastic dome to retain humidity and the plants are allowed to grow exposed to 18 hours of diffused light every day. As the plants will need fresh air for growth, the cover is removed for a few minutes every day. Mild foliar feed like kelp extract is used to mist the cuttings. The formation of roots can be checked by giving the plants a mild tug. Once the roots have formed the clones are transplanted.





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Source: http://www.articletrader.com ]]> http://www.articletrader.com/home-and-family/gardening/air-movement-to-gain-control-over-temperature-humidity-and-co2.html http://www.articletrader.com/home-and-family/gardening/air-movement-to-gain-control-over-temperature-humidity-and-co2.html Mon, 13 Aug 2007 00:00:00 -0500 indoor grow rooms, need a steady supply of fresh air. While this is achieved naturally in outdoor gardens, fields, farms etc., in hydroponics gardening special means have to adopted to ensure air movement for continual supply of fresh air. This is done using fans blowers and associated equipment. As air that becomes stale can no longer support plant growth it has to be vented while fresh air has to be introduced to take its place. Providing a well designed system for the movement of air inside the grow room therefore assumes paramount importance in hydroponics.



Air movement helps maintain ideal levels of several parameters such as temperature, humidity and carbon dioxide in the grow room. These parameters need to be effectively controlled in order to avoid a number of problems. Though complete control over these parameters is not required, some control has to be provided for to ensure that vital plant processes like transpiration are not adversely affected. Transpiration is the process by which water in the plant is evaporated to the surrounding air. Transpiration can happen only when the surrounding the air temperature is within a certain range neither high nor too low. Efficient air movement which ensures heat dissipation and temperature control facilitates transpiration.



Temperature & Carbon dioxide Availability

Though efficient movement of air has a positive effect on a number of processes, its greatest effect is seen on carbon dioxide availability. For photosynthesis to take place, carbon dioxide and light must be available to plants in adequate quantities. Carbon dioxide is naturally present in the atmosphere to the extent of 300 ppm while the light is provided by the lighting system installed in the grow room. Plants in the grow room will, over a period of time, consume the available carbon dioxide necessitating fresh supplies of the gas. In the absence of air movement the process would stop. The venting of carbon dioxide depleted air and addition of fresh, cool carbon dioxide rich air ensures that this does not happen and carbon dioxide is always available for uptake by the plants.



The uptake of carbon dioxide from the surrounding air happens through stomata - microscopic openings on the underside of the leaves. Carbon dioxide absorbed by the stomata is used to make Adenosine Triphosphate (ATP), the major source of usable chemical energy in metabolism. Humidity and temperature ranges trigger the opening and closing of these openings to regulate internal processes. Air temperatures within 65-80 deg. F are ideal for indoor grow rooms. The upper limit can be raised to 85 deg. F with carbon dioxide supplementation. It has been shown that higher temperatures up to 90 deg. F increase the rate of photosynthesis. Beyond 90 deg F, the stomata close to cut excessive transpiration. This starves the plants of carbon dioxide with disastrous effect on yields.



Humidity Considerations

Humidity in the grow room is also an important factor that needs to be controlled as it influences several plant processes. Water is taken up by the plants for normal metabolic processes and excess water is released to the air as water vapor through transpiration. A few gallons of water is thus released by plants in a grow room adding to the humidity. This process is accelerated at higher air temperatures as plants attempt to cool themselves by releasing greater amounts of water vapor. Hence higher temperatures will lead to higher humidity in the grow room.



Relative humidity ranges of 40-60 % are ideal for most plants as optimum carbon dioxide absorption occurs within this range. Higher relative humidity levels affect the carbon dioxide absorption rate as the stomata’s absorption capacity is reduced.



High humidity may also lead to heavy condensation problems. This may happen when temperature drops 10 -15 deg. F, following the switching off of grow lights. In humid conditions this can lead to heavy condensation as the air’s capacity to hold water vapor gets reduced. Water droplets get deposited on grow room surfaces in which colonies of fungi and mold are formed. These may then reproduce releasing spores that can spread throughout the foliage causing extensive damage if left unchecked. The best way to avoid this problem is to ensure that all hot air is vented out of the room so that no condensation can occur.



It can be appreciated from the above that humidity in the grow room cannot be allowed to build up and needs to be controlled. Humidity control in the grow room can be achieved by ensuring movement of air. This can be done in a number ways with varying degrees of efficiency. Perhaps the simplest approach is to install a humidistat and a fan. The humidistat allows for the setting of upper limits on humidity. This does not allow high humidity levels to build up and prevents excessive condensation. Removing this air and moving fresh air in the grow room helps maintain the right conditions for plant growth.



Oscillating Fans

Since the foliage of the plants is where various processes like transpiration, absorption of carbon dioxide etc. take place, oscillation of air around it can create better conditions of temperature and humidity. It has been observed that using an oscillating fan helps mixing of the warm and cool air, reduces humidity around the plants and keeps the stomata open. An additional benefit is the high carbon di oxide content of the new air. Oscillating air also helps in pest control. A number of garden pests become uncomfortable under the high breeze of an oscillating fan and find it difficult to breed in such hostile conditions.



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Source: http://www.articletrader.com ]]> http://www.articletrader.com/home-and-family/gardening/salinity-and-salinity-meters.html http://www.articletrader.com/home-and-family/gardening/salinity-and-salinity-meters.html Thu, 26 Jul 2007 00:00:00 -0500 grow rooms and indoor greenhouses, are completely dependent on supplied water to meet their nutritional needs. It is therefore important that growers gain a basic understanding of certain vital aspects concerning water supply and plant nutrition.



Water is an excellent solvent and whether it is drawn from a tap, a lake, river or other natural sources, contains dissolved impurities along with mineral salts. The salts commonly found in water include common salt (sodium chloride), calcium chloride and carbonates. Plant growth is not adversely affected as long as salinity levels (levels of dissolved salts) are not excessive, but beyond certain threshold limits it can cause extensive tissue damage.



Chemicals used in standard hydroponic nutrient solutions contain only minor quantities of common salt (sodium chloride) which does not normally constitute a problem. Usually, it is the amount of dissolved salts in the water used for making nutrient solutions and the water added to replace the water transpired by plants that can be potentially damaging to plant tissue. Unless this water is purified to remove the salts it can lead to high concentration in the nutrient solution which can cause damage. The dissolved salts are present as anions and cations, which are negatively and positively charged atoms or groups of atoms. These always exist in pairs as so that the net electric charge is zero.



Salinity can be defined as the total amount of soluble salts in the nutrient solution, which is a measure of its conductivity. It can also be defined specifically with reference to the level of sodium chloride in the solution.



Crops vary as to their sensitivity to sodium and chloride ions. Tomatoes, for example can be grown in saline nutrient solutions; in fact common salt (sodium chloride) is added to nutrient solutions to increase conductivity. Higher conductivity of nutrient solution provides improved fruit quality, though yield decreases. On the other hand, plants like lettuce are prone to damage by common salt and high salt concentrations would be disastrous.



Salinity Meters



Growers today, have several types of electronic meters for measuring the salinity of water or nutrient solutions. The more widely used of these are electro-conductivity (EC) and Total Dissolved Solids (TDS) meters. EC meters measure the ability of an aqueous solution to carry an electric current by measuring the electric current between two electrodes. A solution that is rich in nutrients has higher electro-conductivity than a solution with less ionic salts. These meters measure the electro-conductivity in either milliSiemens/cm (mS/cm) or micro Siemens/cm (mS/cm). EC meters are more commonly used by commercial growers because their measurement more accurately corresponds with the best estimate of the strength of nutrient solutions.



TDS meters measure the concentration of a solution as the total weight of dissolved solids. Widely used by hobbyists, they actually measure the electro-conductivity of a solution. They measure the electric current between two electrodes – with a greater concentration of nutrients electric current flows faster than in a solution with a lower concentration. An in-built conversion factor in the microprocessor logic converts the measured current into parts per million (ppm) of total dissolved solids. There is no direct relationship between micro Siemens and ppm for mixtures but with an appropriate conversion factor applied to the measured current a rough estimate of TDS is obtained.



TDS meters can only give a rough estimate of TDS as there are several factors at play including the presence of air bubbles, probe positioning, temperature etc. TDS measurements are indicative of range and pin point accuracy is not possible. However, in the majority of typical applications a range indication is good enough.



Meter Ranges



EC and TDS meters are available in different ranges and not all are suitable for hydroponics applications. There are TDS meters that measure up to 1999ppm, and EC meters that only measure up to 1990mS. These meters, will not be useful for several crops where the optimum electro-conductivity exceeds these limits. For use in hydroponics TDS meters should ideally have a range from 0 to 10,000ppm while EC meters should have a range from 0 to 19.9mS (19,999mS).



Conclusion


Salinity is an important determinative factor in plant growth and growers need to ensure that the water they use has a low salinity. Both EC and TDS salinity meters have been in use in hydroponics in different parts of the world in accordance with the regional preferences and practices. Both types of salinity meters have enabled thousands of growers ensure correct water salinity levels for optimizing plant growth in hydroponics systems. Though much can be said about the need for accuracy, consistency etc. of the measurements, it may be best at times to let practical experience guide user preferences.




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Source: http://www.articletrader.com ]]>