Hydroponic Farmers Federation farm tour – Practical Hydroponics & Greenhouses

Hydroponic Farmers Federation of Victoiria Biennial hydroponic farmers conference and trade exhibition.

The Hydroponic Farmers Federation (HFF)  farm tour will visit Boomaroo Nursery, a world-class vegetable seedling producer, and Thoang’s farm, a truss tomato, strawberry and Lebanese cucumber hothouse producer. This farm tour option is available to registered delegates of the HFF Conference and Trade Exhibition, to be held at the Mantra Lorne Resort, Victoria, from 8-10 June 2016.

Boomaroo Nursery

Boomaroo supplies around 300 million seedlings to growers across Victoria, New South Wales, Queensland and South Australia. The seedling producer is renowned for  high quality commercial seedlings and wholesale greenlife, and its capacity to deliver on time, every time.

The hallmark combination of high quality products, customer service and innovation in seedling production mean that much of the fresh vegetable produce available in supermarkets originates from Boomaroo seedlings, including lettuce, cabbage, broccoli, cauliflower, leek and onions. Located in Lara, Victoria, Boomaroo has 20 hectares under production.

The nursery also specialises in greenlife products, including potted colour (ornamental flowering plants), and are now one of Australia’s largest cyclamen producers.

Beginning as a small family business, Boomaroo was built on the passion of the three Jacometti brothers. Now with over 100 permanent employees, Boomaroo is one of Australia’s largest seedling suppliers and is recognised for its state-of-the-art technology and processes.

For more information on Boomaroo, visit website: http://www.boomaroo.com

Thoang’s farm

Thoang’s farm was established in 1985 by his parents who grew Asian vegetables such as khang kong, mint and bak choi, which were supplied to the Asian grocery shops around Melbourne.

Thoang took over the farming business in 2000. He started to grow tomatoes in a short crop. Along with the tomatoes, he thought he would try growing other crops also, including Chinese broccoli.

In 2012, Thoang decided to try a long crop with grafted plants from Trandos in his low-tech hothouses. The one crop rotation per year has saved him a lot of crop costings and down time.

Thoang's farm Thoang’s farm

This year because of poor tomato pricing, Thoang has invested in growing strawberries in his shade houses and Lebanese cucumbers in his hothouses. This was done because he wanted to diversify his business, in other words, “not to put all your eggs into one basket.” Still, it has been a learning curve for him, but the pricing has been rewarding and he looks forward to the challenge.

For further information and registration, email: eg@asnevents.net.au or visit website: https://members.asnevents.com.au/event/1423   O

Posted 11 May 2016

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Hydroponic Sorghum – Practical Hydroponics & Greenhouses

Sorghum Sorghum (Sorghum bicolor).

The list of crops which can be grown hydroponically is endless. Theoretically, any plant that can be grown in soil can also be grown in a soilless system. Most hobbyists and commercial growers tend to focus on practical or high-value crops that are strongly suited to hydroponics. There are of course some unconventional crops, which can also be profitably grown in a soilless set-up, however impractical they may be. While these crops might not be ideally suited to hydroponics, the applications are sometimes worth pursuing.

By CLIF DROKE

One such crop is sorghum (Sorghum bicolor). Sorghum is in the grass family and is an extremely versatile crop. It can be easily germinated from seed and the plant will tolerate a variety of growing conditions. One of sorghum’s most attractive traits is its tolerance to drought. But while sorghum grows well in arid growing conditions, it absolutely thrives in a hydroponic system in which water and nutrients are constantly available.

There are 25 species of sorghum worldwide, 17 of which are native to Australia. One species is grown for grain while many others are used for animal fodder. The heads of grain sorghum plants can be used to make flour or a nutritious hot cereal, which is valued in less developed countries. Certain types of sorghum seeds can even be popped like popcorn. The plant has also been used in the production of biofuels such as ethanol, and as a sweetener.

My interest in sorghum began with a winter trip to Florida. While driving across the central part of the state just south of Lake Okeechobee, I had the pleasure of witnessing the state’s vast sugar cane fields. Each year I make it my goal to grow something challenging or unusual in one of my hydroponic set ups. This year I was inspired to try sugar cane.

I typically start my plants from seed and was disappointed to find that sugar cane (Saccharum officinarum) is propagated via ‘seed cane’, which involves taking a cut section of the fully mature stalk and planting it in the ground. I was determined to harvest my own sugar cane juice and was upset at the prospects of having to abandon my plans. That’s when I discovered sorghum.

One of the most popular uses of the plant is the ‘sweet cane’ variety of sorghum, which is a close relative of sugar cane. Unlike sugar cane, sweet sorghum can be grown from seed and reaches heights comparable to that of sugar cane, which is anywhere from 12-14 feet at maturity. At harvest, the cane is crushed and yields a juice virtually identical to sugar cane juice in taste and appearance. A little known benefit of sweet cane juice is that it is nature’s perfect energy drink, full of vitamins, minerals, enzymes, and chlorophyll. The natural sugar contained in sweet cane is both delicious and energising. What’s more, it contains less than 15% of the sugar found in the refined version of table sugar we’re all familiar with. Cane juice can also be boiled down into a tasty syrup, known as sorghum molasses.

You might be thinking how cumbersome it would be trying to grow a tall cane-type plant in an outdoor soilless system, let alone an indoor hydroponic system. This doesn’t have to be the case, however. My experiments growing sorghum were surprisingly well suited for both indoor and outdoor crop development. I also found that sorghum plants grew thicker canes and developed faster when grown in soilless media such as rockwool or hydroton than when grown in soil. I also discovered that by harvesting the plants before full maturity I could eliminate the need for using an expensive crushing machine to extract the juice.

I further discovered that by growing certain varieties of sweet sorghum one can even grow the plants indoors under artificial lights from seed to harvest. The ‘Black Amber’ variety is a dwarf-type sorghum, which typically attains a height of six to eight feet, making it practical for greenhouse trials and small-scale indoor applications. It was grown by early American colonists and is still prized today for its sweet golden syrup.

Sweet sorghum sprouted in rockwool cubes. Sweet sorghum sprouted in rockwool cubes.

The type I decided to grow was ‘Red Sweet’ sorghum. I planted the seeds in both Jiffy peat pellets and rockwool cubes. My germination success rate was about 75%. The plants seeded in Jiffy develop faster in the initial stage of growth, but the rockwool seeded plants outperformed in the latter stages of development. Germination occurred in two to four days for most seeds.

One advantage of sprouting sorghum in soilless media is that it can be started several weeks before seeds are usually sown in spring. Consequently, indoor-grown sorghum germinated in the winter will mature months before the sorghum traditionally sown outdoors in spring.

Sorghum Sorghum starts in organic soil (L) and five-inch rockwool cubes (R). This photo was taken approximately one month after germination.

My seeds were germinated in January (our winter here in the US) in my kitchen using a heat mat and a plastic dome tray. Once the seedlings were established I transplanted them either to a soilless potting mix in plastic pots (for the Jiffy pellets) or to larger rockwool cubes. The plants were nursed under 23-Watt CFL lights for several weeks before finally being moved under HID lighting after six weeks. Sorghum can be theoretically grown with full-spectrum fluorescent lights, provided that coverage is adequate for the length of the plant (e.g. three-foot T5 strip lights, both vertical and overhead). Metal halide lamps are the preferred light source, however.

For the nutrient solution I used water-soluble MaxiGro fertiliser (NPK analysis 10-5-14) from General Hydroponics. The solution can be pH adjusted to a 6.5 level of acidity, which allows for maximum uptake of all macro and micro nutrients in sorghum. As the sorghum plant grows it can be transplanted to a bigger pot. Sorghum can be grown to full maturity in a three-gallon (11.4L) plastic pot using a rockwool/hydroton media combination.

The nutrient solution can be hand watered or delivered via automatic irrigation tubes at timed intervals. As sorghum is a very hardy and forgiving plant, the leaves will curl inward when the root zone goes dry, allowing the plant to survive several days before dying. In my experience, a once-daily application of nutrient solution that completely soaks the root zone of a three-gallon pot is all that is required to keep the plants healthy.

Sorghum Potted sorghum plants after three-and-a-half months.

Sorghum grown for syrup should be harvested when the seeds are fully in the dough stage, which is usually about five-and-a-half to six months after seeding. Outdoor harvesting should be done before a killing frost if possible; if not, the crop should be harvested immediately after the freeze. Leaves should be stripped off before the freeze to lessen the damage. Stalks can be juiced using a traditional sugar cane juicer or, if the stalks aren’t too thick, a roller-type pasta maker can be used to extract juice from the cane. The resulting juice can be consumed raw as a refreshing beverage or boiled down further into syrup.

Sweet sorghum is a valuable but overlooked crop in many Western nations, especially the US. While it was once prized by farmers for its hardiness and variety of uses, it has since been supplanted by sugar cane which is valuable only when grown in extremely high volumes. Sorghum is far easier to grow and should be a staple of every serious gardener’s crop lineup. For the hydroponics enthusiast, sorghum offers endless possibilities for experimenting with the technique and viability of soilless production.

About the Author
Clif Droke lives in Topsail Beach, North Carolina, USA, where he has been involved in hydroponics for 13 years. He is the author of the book, Year ‘Round Micro Gardening (ISBN 097925727).  O

PH&G July 2016 / Issue 169

View the original article here

Hydroponic Sorghum – Practical Hydroponics & Greenhouses

Sorghum Sorghum (Sorghum bicolor).

The list of crops which can be grown hydroponically is endless. Theoretically, any plant that can be grown in soil can also be grown in a soilless system. Most hobbyists and commercial growers tend to focus on practical or high-value crops that are strongly suited to hydroponics. There are of course some unconventional crops, which can also be profitably grown in a soilless set-up, however impractical they may be. While these crops might not be ideally suited to hydroponics, the applications are sometimes worth pursuing.

By CLIF DROKE

One such crop is sorghum (Sorghum bicolor). Sorghum is in the grass family and is an extremely versatile crop. It can be easily germinated from seed and the plant will tolerate a variety of growing conditions. One of sorghum’s most attractive traits is its tolerance to drought. But while sorghum grows well in arid growing conditions, it absolutely thrives in a hydroponic system in which water and nutrients are constantly available.

There are 25 species of sorghum worldwide, 17 of which are native to Australia. One species is grown for grain while many others are used for animal fodder. The heads of grain sorghum plants can be used to make flour or a nutritious hot cereal, which is valued in less developed countries. Certain types of sorghum seeds can even be popped like popcorn. The plant has also been used in the production of biofuels such as ethanol, and as a sweetener.

My interest in sorghum began with a winter trip to Florida. While driving across the central part of the state just south of Lake Okeechobee, I had the pleasure of witnessing the state’s vast sugar cane fields. Each year I make it my goal to grow something challenging or unusual in one of my hydroponic set ups. This year I was inspired to try sugar cane.

I typically start my plants from seed and was disappointed to find that sugar cane (Saccharum officinarum) is propagated via ‘seed cane’, which involves taking a cut section of the fully mature stalk and planting it in the ground. I was determined to harvest my own sugar cane juice and was upset at the prospects of having to abandon my plans. That’s when I discovered sorghum.

One of the most popular uses of the plant is the ‘sweet cane’ variety of sorghum, which is a close relative of sugar cane. Unlike sugar cane, sweet sorghum can be grown from seed and reaches heights comparable to that of sugar cane, which is anywhere from 12-14 feet at maturity. At harvest, the cane is crushed and yields a juice virtually identical to sugar cane juice in taste and appearance. A little known benefit of sweet cane juice is that it is nature’s perfect energy drink, full of vitamins, minerals, enzymes, and chlorophyll. The natural sugar contained in sweet cane is both delicious and energising. What’s more, it contains less than 15% of the sugar found in the refined version of table sugar we’re all familiar with. Cane juice can also be boiled down into a tasty syrup, known as sorghum molasses.

You might be thinking how cumbersome it would be trying to grow a tall cane-type plant in an outdoor soilless system, let alone an indoor hydroponic system. This doesn’t have to be the case, however. My experiments growing sorghum were surprisingly well suited for both indoor and outdoor crop development. I also found that sorghum plants grew thicker canes and developed faster when grown in soilless media such as rockwool or hydroton than when grown in soil. I also discovered that by harvesting the plants before full maturity I could eliminate the need for using an expensive crushing machine to extract the juice.

I further discovered that by growing certain varieties of sweet sorghum one can even grow the plants indoors under artificial lights from seed to harvest. The ‘Black Amber’ variety is a dwarf-type sorghum, which typically attains a height of six to eight feet, making it practical for greenhouse trials and small-scale indoor applications. It was grown by early American colonists and is still prized today for its sweet golden syrup.

Sweet sorghum sprouted in rockwool cubes. Sweet sorghum sprouted in rockwool cubes.

The type I decided to grow was ‘Red Sweet’ sorghum. I planted the seeds in both Jiffy peat pellets and rockwool cubes. My germination success rate was about 75%. The plants seeded in Jiffy develop faster in the initial stage of growth, but the rockwool seeded plants outperformed in the latter stages of development. Germination occurred in two to four days for most seeds.

One advantage of sprouting sorghum in soilless media is that it can be started several weeks before seeds are usually sown in spring. Consequently, indoor-grown sorghum germinated in the winter will mature months before the sorghum traditionally sown outdoors in spring.

Sorghum Sorghum starts in organic soil (L) and five-inch rockwool cubes (R). This photo was taken approximately one month after germination.

My seeds were germinated in January (our winter here in the US) in my kitchen using a heat mat and a plastic dome tray. Once the seedlings were established I transplanted them either to a soilless potting mix in plastic pots (for the Jiffy pellets) or to larger rockwool cubes. The plants were nursed under 23-Watt CFL lights for several weeks before finally being moved under HID lighting after six weeks. Sorghum can be theoretically grown with full-spectrum fluorescent lights, provided that coverage is adequate for the length of the plant (e.g. three-foot T5 strip lights, both vertical and overhead). Metal halide lamps are the preferred light source, however.

For the nutrient solution I used water-soluble MaxiGro fertiliser (NPK analysis 10-5-14) from General Hydroponics. The solution can be pH adjusted to a 6.5 level of acidity, which allows for maximum uptake of all macro and micro nutrients in sorghum. As the sorghum plant grows it can be transplanted to a bigger pot. Sorghum can be grown to full maturity in a three-gallon (11.4L) plastic pot using a rockwool/hydroton media combination.

The nutrient solution can be hand watered or delivered via automatic irrigation tubes at timed intervals. As sorghum is a very hardy and forgiving plant, the leaves will curl inward when the root zone goes dry, allowing the plant to survive several days before dying. In my experience, a once-daily application of nutrient solution that completely soaks the root zone of a three-gallon pot is all that is required to keep the plants healthy.

Sorghum Potted sorghum plants after three-and-a-half months.

Sorghum grown for syrup should be harvested when the seeds are fully in the dough stage, which is usually about five-and-a-half to six months after seeding. Outdoor harvesting should be done before a killing frost if possible; if not, the crop should be harvested immediately after the freeze. Leaves should be stripped off before the freeze to lessen the damage. Stalks can be juiced using a traditional sugar cane juicer or, if the stalks aren’t too thick, a roller-type pasta maker can be used to extract juice from the cane. The resulting juice can be consumed raw as a refreshing beverage or boiled down further into syrup.

Sweet sorghum is a valuable but overlooked crop in many Western nations, especially the US. While it was once prized by farmers for its hardiness and variety of uses, it has since been supplanted by sugar cane which is valuable only when grown in extremely high volumes. Sorghum is far easier to grow and should be a staple of every serious gardener’s crop lineup. For the hydroponics enthusiast, sorghum offers endless possibilities for experimenting with the technique and viability of soilless production.

About the Author
Clif Droke lives in Topsail Beach, North Carolina, USA, where he has been involved in hydroponics for 13 years. He is the author of the book, Year ‘Round Micro Gardening (ISBN 097925727).  O

PH&G July 2016 / Issue 169

View the original article here

Water quality needed for different hydroponic crops? – Part 2 – Practical Hydroponics & Greenhouses

Following on from last month’s question on water quality, here are some more guidelines. These list the Dutch guidelines for the maximum levels of sodium that are acceptable in recirculating solutions for a range of crops.

I have also included more recommendations as to different water sources, especially the collection of rainwater.

Answer by RICK DONNAN

The quality of the raw water going into a hydroponic system is very important, especially if the system is recirculating (‘closed’). The ion most likely to cause problems is sodium (Na+).

Build-up of non-essential ions at constant EC. Figure 1. Build-up of non-essential ions at constant EC.

Build-up of sodium
Most recirculating systems are managed on the basis of maintaining constant EC (electrical conductivity—a measure of solution strength) of the recirculating solution. However, EC tells you nothing about the individual ions that make up that solution. Unfortunately, when non-essential ions, such as Na, are added in with the raw water at strengths higher than the plants take up, then their concentration will rise. This is shown in Figure 1, which indicates their increase with time.

When this happens there is a double whammy. The non-essential ions, such as Na, are increasing towards toxic levels. At the same time, the effective nutrient content of the solution is shrinking. That is, the plants are heading towards a mixture of being both poisoned and starved. Not a good combination.

Table 1. Maximum level of Na recommended for recirculating systems. Table 1. Maximum level of Na recommended for recirculating systems.

Maximum Na level in recirculating solutions
Table 1 giving recommended maximum levels of sodium in recirculating solutions for different hydroponic crops is based upon information given in ‘Bemestingsadviestbasis Substraten’, published by Proefstation voor Bloemisterij en Glasgroente, The Netherlands.

The original information is given in molar units (millimole/litre). A mole is the molecular weight of a molecule expressed as gram/litre. For an atom such as Na, molecular weight is the same as atomic weight, which for Na is 23. Because ppm (parts per million), also expressed as milligram/litre), is the unit commonly used in Australia and some other countries, I have also converted the molar units to ppm.

Water source
In the previous issue, I mentioned using reverse osmosis to remove the ions from input raw water that had too high a content of unwanted ions, such as Na. There is another possible source of water sometimes pure enough to use. This is rainwater, but care needs to be taken, apart from availability, dependent upon the frequency and quantity of rainfall.

Excess salt accumulates in the tomato plant in the older leaves. Leaves turn yellow, and will eventually fall off. The plant is stunted and not vigorous, but other symptoms may be lacking. Tomatoes are relatively salt tolerant. (Image Texas A&M AgriLife Research) Excess salt accumulates in the tomato plant in the older leaves. Leaves turn yellow, and will eventually fall off. The plant is stunted and not vigorous, but other symptoms may be lacking. Tomatoes are relatively salt tolerant. (Image Texas A&M AgriLife Research)

Rainwater which has flowed over the ground could to be contaminated with soil borne pathogens. Consequently, it is dangerous to use stream or dam water without it being sterilised. Sometimes growers get away with not sterilising if they are in an area with no other horticultural or agricultural activity. Often, this may last for a year or two (the honeymoon period), but usually disaster eventually strikes.

Rain collected off greenhouse, etc, roofs is usually cleaner, but is still risky if not sterilised, especially if in a dusty area.

Other aspects to watch are that if near the sea, sea mist and drift can result in high levels of salt collecting in the rain water. Also, do not collect water from galvanised roofs—a little zinc dissolved from the galvanised layer can give levels of zinc in the water which are toxic to plants. O

PH&G July 2016 / Issue 169

View the original article here

Hydroponic Lighting | Season-extending technology – Garden Center Magazine

COURTESY OF NORTHWEST SEED & PET

The changing of the seasons makes it difficult — but not impossible — to grow and garden year-round. Indoor gardening fills this niche but demands a sharp technological edge to be feasible.

At Northwest Seed & Pet in Spokane, Wash., customers are particularly interested in indoor growing technology. With lighting and hydroponics systems from Hydrofarm, owner Bob Mauk is able to meet this need. Mauk says he has been stocking Hydrofarm products at his two locations for about 10 years.

“I think my primary reason for going to them in the first place was lighting and hydroponic gardens,” Mauk says. “Indoor lighting [has] become a bigger deal, a little more specialized. We do get a lot of planters, fertilizers and a little bit of everything in that grow operation. The customers we’re dealing with that are wanting to start herbs and vegetables and things like that indoors, [Hydrofarm’s] seems to be a better unit.”

In his market, Mauk says indoor growing is a popular activity, and Hydrofarm systems are also intuitive enough to be accessible for newer indoor gardeners.

COURTESY OF NORTHWEST SEED & PET

“I think the advances in fluorescent lighting are what got me more interested, extending our gardening season through the winter, getting more people to do indoor gardening as well under lights,” Mauk says. “Some of the hydroponics kits were a little more of an easy sell for customers who hadn’t done it before and weren’t looking for some kind of huge operation, they just wanted to have something they could grow.”

There are other sources for indoor growing systems available to Northwest Seed & Pet, but Mauk says Hydrofarm stands out from the competition with its focus on innovation and pioneering of new techniques and technologies.

“Hydrofarm has seemed to kind of stay ahead of it,” Mauk says. “More advances in some products and movement toward LEDs and some of the newer lighting. They’re pretty innovative, or at least they try to stay on top of what works in the marketplace.”

Products from Hydrofarm have become such a staple at Northwest Seed & Pet that the company’s two stores have made structural changes to accommodate a larger lighting and hydroponics section.

“They’ve been an excellent company,” Mauk says. “We added space from about a 10-foot [shelving] set to about a 40-foot set in both of my stores as far as lighting is concerned. We’ve increased our square footage, which consequently has increased our sales in that category. They’ve worked with us all [through] that.”

Tips for Havesting your Hydroponic Garden

The harvest is one of the most enjoyable parts of  running an indoor garden; It is your reward for all of the time and energy you have put into it.

Generally speaking, healthy, well maintained plants are going to produce plentiful harvests, but there are plenty of additional things you can do to get the most out of your plants.

Pre-Harvest Tips:

To avoid the taste of organic or chemical fertilizers, you should flush the garden with plain water 10 to 14 days before harvesting. Some gardeners will use fertilizers up to 3 or 4 days before harvesting and use clearing solutions to remove the fertilizer residue.If you are growing herbs that will be dried, do not water them for 1 or 2 days before harvesting them. The soil should be mostly dry, but not too dry to where the plants begin to wilt. Done correctly, this will reduce your drying time by about a day and will not in any way effect the end product.

Harvest Tips:

Harvest timing is critical, as plants and fruits need to be harvested at the moment of peak ripeness. This window is very small, usually between 5 to 7 days.Growth of the plant or fruit will stop at harvest. Make sure to keep plants from prolonged exposure to the light, temperatures above 80°F, excessive friction, or damp/humid conditions.

Tags: Best Hydroponic System, Commercial Hydroponics, Garden Grow Lights, Hydroponic Drip System, Hydroponic Gardening Supplies, Hydroponic Shop, Hydroponic Solution, LED Growing Lights, Online Hydroponics

This entry was posted on Wednesday, April 21st, 2010 at 7:06 pm and is filed under Hydroponic Growing System. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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Water quality needed for different hydroponic crops? – Practical Hydroponics & Greenhouses

I am considering setting up a small commercial hydroponic farm using a recirculating system. I have read that water quality is very important for hydroponics, especially when recirculating. Is this correct and can you give me some guidelines as to the quality required to grow different crops in hydroponics?

Answer by RICK DONNAN
Yes, the quality of the raw water going into a hydroponic system is very important. The most significant chemical naturally occurring in water supplies is common salt (sodium chloride, formula NaCl).

In a ‘closed’ recirculating system, every time the salt build up is displaced from the system, it is returned to become part of the feed into the system. Hence, if the Na in the added raw water is higher than the crop can take up, the Na level in the recirculating solution will continue to rise. However, in an ‘open’, free drainage, system any modest build up of Na stabilises, because any excessive build up is pushed out of the system by the next irrigation cycle.

Salt or EX toxicity High salt or EC: These cucumber leaves appear dull and leathery.?A narrow yellow border develops around the leaf margin. (Image NSW Industry & Investment)

Crop sensitivity to sodium chloride
Different crops have different sensitivities to sodium chloride, although it is sodium which usually has the major impact. The Dutch have been studying this problem for many years and their results for vegetables and cut flowers follow:

Vegetable sensitivity to salt
Very sensitive
• Bean
• Strawberry

Sensitive
• Cucumber
• Capsicum
• Egg Plant
• Melon
• Lettuce

Tolerant
• Tomato
• Spinach
• Endive
• Radish

Cut flower sensitivity to salt
Very sensitive
• Anthurium
• Cymbidium

Sensitive
• Hippeastrum
• Gerbera
• Alstroemaria
• Rose
• Anemone
• Tulip
• Chrysanthemum
• Bouvardia

Tolerant
• Carnation
• Euphorbia fulgens
• Gypsophila
• Freesia

(From: Wageningen UR. (2014) Kwantitatieve Informatie voor de Glastuinbouw.)

Salt or EC toxicity Salinity causes wilting. Leaves appear dull and dark green and cup downwards. (Image NSW Industry & Investment)

Reducing Na levels
Unfortunately there is no way of removing only sodium ions from a solution. If the level of Na in your raw water is too high for the crop you are growing, then if you have a recirculating system your only choice is to install reverse osmosis (RO).

Reverse osmosis equipment mainly consists of tubular cells made of semi-permeable membrane. When pressurised these allow water to pass through, but block the passage of all dissolved ions including Na and Cl, as well as all nutrient ions. The result is chemically (and biologically) clean water. This is perfect for use in recirculating systems, and especially for salt sensitive crops.

One aspect of installing RO equipment is that you need to be able to handle the waste (brine) stream from the unit, which contains all the incoming salts. For example, say you have a unit that recovers 50% of the input as pure water. The brine stream will be the other 50% of the input, but contains all the salts, hence it will be twice as strong as the initial water supply.
Another aspect of RO to watch is that a major operating cost is the replacement of the expensive membranes. Ensure that you purchase your unit from someone experienced, because proper pre-treatment of your raw water is essential to prolong the life of the membranes.

‘Hard’ water
Water coming off limestone will often be “hard’, that is, it contains calcium (Ca) and bicarbonate (HCO3) and perhaps magnesium (Mg) ions. These are usually OK to use provided they are the only significant dissolved solids. Because the Ca and Mg are nutrients they can be used, however, the Ca and Mg in your fertiliser formulation must be adjusted downwards to make allowance for these free nutrients.

The bicarbonate will raise the pH and hence needs to be neutralised with acid, typically phosphoric or preferably nitric. Again, your fertiliser formulation must be adjusted to make allowance for the extra phosphate or nitrate ions added as part of the acid.

Iron and boron
Although iron (Fe) is a nutrient, in water supplies it is much more of a problem than a benefit. This is because it oxidises and hence is useless as a nutrient and also can cause dripper blockages. This is why hydroponic fertilisers have their iron in a stable chelated form. Iron in the raw water can be removed by aeration followed by settling or filtration.

A problem in some countries, but rarely in Australia, is water with too high a boron (B) content. O

June 2016 / Issue 168

View the original article here