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Tue Aug 09, 2016 11:42 am


CONTROLLING THE ENVIRONMENT

How Important Is Water Quality In Hydroponics...

Water quality is an important determinative factor in hydroponics cultivation. Water is the basic ‘carrier’ in hydroponics as it dissolves and transports nutrients for plants. However, water also dissolves a lot of impurities that can be harmful to plants. These impurities cannot be easily detected visually, and it is all too easy to be misled into making wrong assumptions about the purity of water from the clarity of a sample.

Fortunately, solutions to water quality problems, in the majority of cases, are simple and do not involve complicated methods and techniques. Even small growers can use some simple and proven techniques to effectively solve their water quality problems. The types of water quality problems that growers will likely face depends on the water source from which they draw water for their hydroponics garden. Poor water quality can lead to a number of plant growth problems including stunted growth, mineral toxicity or deficiency symptoms, build up of unwanted elements in plant tissue, bacterial contamination, etc. Though causes of poor water quality are numerous and varied some of the more frequently encountered of these are

1. Chlorination

Chlorination is the most extensively adopted measure to control bacterial contamination of water supplies in cities, towns and other urban centers. In hydroponics cultivation, the use of chlorine by growers to kill pathogens in their water has caused problems in a number of instances. It was found that this happened due high levels of active chlorine in the water used to make nutrient solution. Chlorinated water sources need to be aerated in a ‘holding tank’ for 48-72 hours (depending on the initial concentration), with good ventilation during which time the active chlorine levels fall to below 1ppm, a safe level for the plant’s root systems. Chlorine in nutrient solution water is known to cause damage to several crops especially to sensitive crops such as lettuce, salad greens, strawberries and others.

2. Unwanted minerals

Water being an excellent solvent dissolves a large number of substances including minerals. While some of these are beneficial, others like sodium, for instance, are quite harmful. Plants do not require sodium and sodium chloride if present in water can cause problems even in small quantities. Sodium can be very harmful especially in re-circulating systems. Plants differ widely in their sensitivity to sodium; some plants like tomatoes can tolerate much higher levels of sodium than other plants such as lettuce. Sodium needs to be kept below 80 ppm for healthy growth of most plants, but below 30 ppm for plants such as lettuce.

Magnesium, calcium, potassium, sulfur, nitrates and trace elements such as boron, copper, manganese and zinc may be present in water from various water sources. This can be taken care of in most cases by suitably adjusting the nutrient formulas to factor in the presence of these elements thus preventing accumulation and toxicities in the water supply. The presence of trace elements can be more troublesome and may require demineralization and dilution of the water source with pure water supply when using in nutrient solutions.

3. Microbial or pathogen contamination

Water from sources such as wells, ponds streams etc. often contains organisms that should be removed before the water can be used in nutrient formulations. The most common of these ‘pathogens’ is Pythium, which can attack plants when present in sufficient spore concentration. Growers have successfully used chlorination as a line of defense against these pathogens, but it requires that the chlorinated water be held for a few days to allow to the concentration of chlorine to drop to levels tolerable to plants. Hydrogen Peroxide can also be used to kill pathogens such as Fusarium wilt and Pythium in water and nutrient solutions.

4. Iron and Iron bacteria

Iron in the form of iron hydroxide is usually present in water from ground water sources near areas with deposits of iron sand or iron ores. The iron hydroxide in water, though not directly harmful to plants presents a number of problems due to the blockages it causes in various components of the system. These blockages if not removed, from an ideal medium for growth of iron bacteria, which consume a variety of elements that are provided for plant growth in hydroponics systems. Iron hydroxide removal methods include aeration and settling or flocculation with different agents. Iron bacteria can be removed by sterilization of the water or nutrient solution.

5. Hard water sources

Water is termed ‘hard’ when it contains substantial amounts dissolved calcium bicarbonate and other elements. When in contact with pipes and equipment the calcium bicarbonate changes to insoluble calcium carbonate also known as lime scale. Hard water forms scale in irrigation pipes, heating elements and pumps causing severe blockages. Computerized water conditioner units similar to the ones used in domestic water supplies can be used to eliminate scaling problems in hydroponics systems.

6. Herbicides

Cases of herbicide contamination of ground water sources and even municipal water supplies are not unknown. Herbicide contamination manifests as damage to sensitive crops such as tomatoes. Activated carbon filtration can help reduce damage but care must be taken to replace the carbon often enough to enable it to retain its efficiency.

Summary

Pure, clean water is essential for healthy plant growth and growers can give the best start to their plants by investing some time and effort in ensuring water quality. Water quality problems are often easy to solve provided they are properly identified. The best approach is to be proactive about water quality as assumptions based on water clarity, absence of visible contamination etc. may be quite misleading.
Image What is the correct water temperature for hydroponics...

You should maintain a constant temperature between 70° and 80°F (21-26° Celsius) in your nutrient reservoir. This is important, especially during the cool months, to help increase plant performance. Do not increase the temperature above 85°F (29° Celsius) as this may cause root damage.

You can use an aquarium heater to maintain the temperature in your reservoir. It takes at least 5 watts per gallon to heat and maintain a constant nutrient temperature (for example, a 10 gallon reservoir requires a 50 watt heater).
Image Is humidity important...

Humidity levels can become very high in your hydroponic growing area due to consistent watering and the enclosed environment.There are monitoring devices to help you keep a check on the humidity level. This is another area where correct ventilation and fanning helps. Your plants can either become saturated or too dry, and neither is very healthy.
Image How effective is CO2...

There is no question that increasing carbon dioxide levels in the garden has tremendous potential for creating faster, more productive crop plants. The trick is to use Co2 wisely – knowing how and when to add Co2 for maximum results.

The first step is to create such great growing conditions in your garden that your crops will benefit from extra Carbon Dioxide! Careful attention to light levels, temperature, air flow through the garden, exhaust fan capability, air intake, crop spacing, and nutrient supply will result in a first class garden. You will have healthy, vigorous plants ready and willing to take up and use extra Co2 efficiently. Overheated, crowded, and bug-infested plants are so busy just trying to survive that adding Co2 would be wasteful. Whip your garden into shape first – then plan when and where to add Co2 to get the greatest benefits.

Our plants go through several growth stages during their lives 1) seedling/cutting stage, 2) transplant, 3) green growth, 4) transition to flowering and crop production and 5) production stages. Each growth stage has its own “cultural” requirements. Seedlings need different light levels and fertilizer strengths than established crop plants. Extra Co2 is more useful during some growth stages than others. Generally, adding Co2 will help the most, during periods of rapid growth, but a team of Canadian university researches and commercial growers have discovered some surprising and useful facts about carbon dioxide’s effects on specific stages of growth and how extra Co2 early in a plant’s life brings unexpected benefits months later.

The researchers and commercial growers discovered that adding Co2 to plants at the seeding/cutting stage for about two weeks produced two benefits; faster early growth and greater final crop yield, even without extra Co2 during green growth and crop production. This is useful information for hobby gardeners since a little extra carbon dioxide for rooting cuttings and seedlings can help plants so much.

If you use tall, clear covers over your baby plants, release a little Co2 under the cover to raise Co2 levels to about 1500 ppM. Remove covers to let in fresh air after a few hours, and be sure plants have only fresh air (no Co2) during dark periods. The two-week period leading up to transplanting is the most effective time for this Co2 technique. If you are already using Co2 for other purposes, try treating your “small fries” with this proven growth and crop stimulator.

Adding carbon dioxide during transplanting stage is not recommended, since plants are adjusting to new growing conditions and can make do with regular Co2 levels (average 300 PPM) in the air.

Once plants are ‘established’ in green growth stage (full light levels, full strength fertilizers, spreading roots and new top growth), it’s time to consider adding Co2 to your rapidly growing green plants. Your decision should be based on the length of time your crop will be in green growth as well as an impartial evaluation of the garden’s growing conditions. Plants with a long green-growth period (30 days and more) would benefit from Co2 enrichment, growing to a desired size more quickly. Growth hormones used along with extra Co2 and increased food strength, results in faster, healthier green growth plants.

Some crops, called ‘long day’ plants produce their crops during summer, while continuing to put out new leaves and stems. Tomatoes and roses are typical long-day crops, which benefit from supplemental Co2 right through the green growth/crop production stages. These plants do not go through a separate transition stage like short-day crops, so additional Co2 can be applied through the life of the plants during the light cycle.

“Short-Day” crops have a definite “transition” stage before flower or crop production begins thus upsetting Co2 applications. Short-day plants produce green growth during spring and summer and flower flower and crop in autumn, responding to the longer nights by beginning crop production. Chrysanthemum and hardy hibiscus are examples of this category of plant.

Since Co2 is most useful when established plants are actively growing, shut off your tank until crops pass through the transition stage and save the extra Co2 for use when crops begin producing flowers. Holding off on extra carbon dioxide while plants go through the transition from growth to crop production should help keep plants bushy and compact while they decide what to do next and reduces ‘stretching’ problems so common in the early transition period. In fact, if your short-day crop has a history of stretching, cut off the extra Co2 two week before the end of the green growth stage.

Once crops are ‘established’ into crop production stage (full light levels, full strength food, plants actively producing) resume Co2 enrichment. If all goes well, you could consider increasing the nutrient strength for periods of maximum growth during this stage. Cut back on Co2 as growth slows and crop is finishing up.

After 7-14 days, your crops tell you how many plants you are gaining from extra Co2. How much is it helping your crop plants?

You can re-position oscillating fans, add Co2 airlines to more oscillating fans or increase Co2 flow rate if growth rate is uneven or if some plants need more Co2. Usually growers become very enthusiastic about adding Co2 at this point since they can see how it is helping their gardens. If little or no effect on growth is seen, check growing conditions for limiting factors. High garden temperatures, poor air movement, bugs, disease or incorrect nutrient mix all interfere with Co2 uptake and growth.

The Co2 generators we use for carbon dioxide enrichment are very efficient burners of propane or natural gas. By completely oxidizing the fuel, the generator gives off pure carbon dioxide and lots of heat as water vapor! Growers planning to install Co2 generators in their gardens should anticipate having to deal with excess heat and humidity from their new equipment. We approach this problem a number of ways.

One method involves placing the generator in a remote location and moving the Co2 through ducting to the air intake where it is delivered to the crop by oscillating fans. A fan attached to the duct draws the Co2-rich air from the generator, helping to dissipate heat and causing some of the water vapor to condense inside the duct. Catching condensation run-offs will help in removing condensation from the duct. Do this by sloping the duct slightly and placing a tray or bucket at the end.

Another method is to suspend the generator over-head, above the garden, and use timers or controls systems to supply Co2 for brief periods during the light hours. With all fans shut off, the Co2 generator goes on and carbon dioxide drifts downward onto the garden. When the generator shuts off by timer or thermostat, the fans are turned back on to cool the garden.

The disadvantages of this method are:

• Periods of high temperatures in the garden with no air movement.

• Limited amount of Co2 supplied to the garden

• Excess humidity levels in the garden


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