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Growing hydroponic vegetables by Malcolm Campbell

 Sure the idea of going into a Hydroponic supply shop seems to be only for the adventurous, but you can grow almost any plants without any soil or even soil-like media in a saturated nutrient solution, hydroponically. This may seem anathema to the organic gardener, but its practical acceptance came about by demonstration on the Himalian slopes of West Bengal near Kalimpong in India during 1946-7. The individual, who did more to popularise the art or science of hydroponics, depending on your point of view, was Sholto Douglas. His book Hydroponics the Bengal System was in its fifth edition by Oxford University Press in 1975 when I added it to my library and may still be in print. Douglas would not have had the temerity to claim to have discovered the technique, but he certainly demonstrated its application on the broadacre as no-one previously had done. There are, incidentally, lots of more recently written books available, Simple Hydroponics by AC Sundstrom, published by Viking O'Neil, RRP $19.95 is the ideal beginners manual with a local bias.

The technique

The principle of hydroponic culture is that while the whole media is saturated only a small portion of the media in the bottom of the container is liquid, so that about 80% of the air spaces above the liquid is moist, but only a small part is saturated. This provides good drainage, aeration and moisture from the nutrient-rich liquid, so the plants are in growth mode all the time.

Quite simply, hydroponic culture requires that you saturate a neutral media with a nutrient solution. The media provides drainage and anchors the roots as they grow. The most popular media is Perlite. Made locally it is light yet has a high moisture retention capacity. However any of the following are also suitable. Vermiculite, a fine gravel, clean washed sand, Rockwool/Growool or reconstituted and recycled poly products which have more recently been used to good effect. The initial cost of Perlite is worth the outlay, because the product is used again and again, whereas Vermiculite Grade 3, breaks down and finishes up as a rather slushy mess. On the other hand if you are trying to grow lettuce at Eucla then the extra water-holding capacity of Vermiculite is a real plus over gravel, which might be the ideal media at Cooma. Grey Gravel warms up more quickly in Winter and can push some very early season Carrots and Lettuce along very rapidly. If using gravel it is best to use a non porous type because they are usually more inert, so their pH has little or no influence on the uptake of the nutrient solution. Marble chips are excellent if you have access to a friendly monumental mason in your neighbourhood.

Fortunately the nutrient used to saturate the media is commercially available from a plethora of outlets and it is comforting to the average user that you don't have to be an industrial chemist to apply the stuff. Most require only a few grams dissolved into some tepid water then added to the hydroponic containers. The several hydroponic growers I know use the same mixture for all their crops and don't seek to reconstitute the solution with the elements that have been absorbed. To the chemist that's the real challenge: to be able to keep adding the chemical compounds at the rates of usage by the vegetable or whatever else you choose to grow. Mushrooms are about the only common 'vegetable' crop that you are unable to grow hydroponically. They are a fungi of course and the chemical compounds in the nutrient will kill them, as you will have discovered if you grew mushies in your lawn and then fertilized the lawn with chemical fertilizers.

The nutrient is added in solution to water-tight containers at regular intervals, say weekly or at the very most in the growing season, fortnightly. The liquid nutrient can be topped up as it evaporates or utilised by the plants or it can drained totally at the week's end. In areas with high rates of evaporation or a salty water supply, such as my friends in Marla have, the concentration of salts gets a bit high after a week so they drain the whole solution and replenish it rather than exacerbate the problem with lots of top ups that increase the level of undissolved salts. Curiously most vegetables can tolerate fairly high levels of saline salts when the media is constantly moist. It's when things dry out that the trouble starts. The discarded depleted nutrient solution can be added to any undiscerning soil crop. My Horseradish thrives on the discards.

One hydroponic system that I favour has polystyrene foam containers with a PVC tube and a float in the tube that indicates the liquid level. These are known to agronomists as piezometers and can sum up the situation at a glance.

Site

The containers are best located in the same warm open sunny aspect as you would cultivate a crop in the ground. The big advantage though is that you can grow the same crops much earlier in a poly igloo or glasshouse or even outside in frost-free sites, because the media warms faster than most soils.

The hydroponic advantage

Because there is no soil, there are no weeds, no digging, no soil-borne diseases nor any need to rotate crops. And there's certainly no cultivating. These advantages are appealing to the gardener who hates to weed or is limited in any physical activity. Hydroponic culture also appeals to the gardener who wants total domination over their labours and for gardeners with limited time to dedicate to their hobby or indeed limited space in which to practice it.

The taste test

Organic purists may denigrate the taste of artificially grown hydroponic vegetables, but from my own taste tests they are delicious and if anything, much larger and certainly more robust than much organically grown produce. There is absolutely no chemical taste about the vegies and you simply won't believe the size of root vegetables grown this way.

I've seen show-bench quality parsnips 500mm long and 150mm thick grown in specially constructed poly sleeves, with no forking. Succulent lettuce and prolific cherry tomatoes are a breeze in the hydroponic media.

Sowing

While sowing seed is possible the beginner may prefer to plant commercially grown seedlings. If you choose to buy punnet seedlings, wash the soil or soil-based media from them, then soak in a diluted hydroponic nutrient solution until they become turgid, before planting. This assures an instant 'take' and they start growing without the usual check in growth if planted in soil.

For raising your own seedlings you will need a fine grade (Number 1) of Vermiculite as the seed raising media. Crops like carrots can be raised in shallow furrows of Vermiculite laid on top of your Perlite media, so that no transplanting is required, once the seed has germinated.

Red Beet, Silver Beet and the Golden Beets jump out of the media when grown hydroponically and even Sugar Peas and Snow Peas thrive.

Asian Vegetables that prove a bit slow in the South, like "Mong To-e" Basella rubra ,"Rau Munong" or "Water Spinach" Ipomœa aquatica and "Galangal" Languas galanga , can be grown to perfection, hydroponically.

Final word on culture

If you are keen to try growing herbs hydroponically, you might want to dilute the solution used, because most Mediterranean herbs yield their best flavours when grown fairly hard, with low nutrients. Parsley and Basil thrive on the nitrogen-rich solution, but Marjoram and Chives are best in a diluted solution. Whatever your vegetable preferences, hydroponics is certainly worth a try.