Hydroponics Basics


The word hydroponics comes from the Greek words hydro (water) and ponos (to work) and literally means ‘water work’. The first hydroponic systems come from antiquity. In fact, The Hanging Gardens of Babylon, and the floating gardens of China and Aztec Mexico. Early Egyptian paintings also depict the growing of plants in water. Thanks to the continuous flooding it was possible to cultivate food the whole year round.

English philosopher Sir Francis Bacon (1561 – 1626) published the book Sylva Sylvarum , which is the earliest known book on growing plants without soil. 1600, Belgian physicist Jan Baptista van Helmont (1579 – 1644) demonstrated that a willow shoot kept in the same soil for five years with routine watering gained 160 lb (13 kg) in weight. As it grew into a full-sized plant, the soil in the container lost only 2 oz (57 g). Clearly, the source of most of the plant ’ s nutrition was from the water, not the soil.

The basis for modern hydroponic systems was laid after the experiments that took place from 1895-1865 done by German scientists Von Sachs and Knop with growing plants in water-nutrient solutions, calling it nutriculture. They discovered that plants needed certain nutritional elements to develop. The first successful hydroponic systems were developed in the thirties by Dr. Gericke in the American state of California. During the Second World War these systems were adapted to provide American soldiers with fresh vegetables. The first hydroponic systems were adapted for commercial purposes for the production of vegetables and flowers in the seventies and eighties.

Hydroponics is the process of growing plants in a mixture of mineral nutrients and water; specifically without the use of any type of soil. The two major features of hydroponics are the use of liquid solutions for plant growth and the support of plants with porous materials, such as pebbles or gravel, which let the nutrients into the roots. Plants usually grow by using mineral nutrients from soil and non-mineral nutrients from air and water. With the use of hydroponics, plants do not get the nutrients usually taken from the soil. However, plant physiologists provide each type of plant with the correct amount of each nutrient needed to grow without soil. In the eighteenth century, solutions containing mineral nutrients were first developed. 

Almost every hydroponic garden starts with the same four parts, a grow bed, nutrient reservoir, grow media nutrient solution. It sounds simple, but the first two usually cause the most agony for many new gardeners. You probably will ask yourself, "Where should I start?"- build from scratch (too complicated for many), buy an existing manufactured system, or use ordinary gardening creativity with existing materials, modified to meet the basic requirements.

A distinction can be made between ‘real’ hydroponic systems in which plants are cultivated without using substrate (NFT, aeroponics) and hydroponic systems that use a substrate (rock wool, perlite, coco, clay pebbles and peat). The type of nutrient that must be used depends on the type of system.

An important distinction can also be made between open and closed systems. In open cultivation systems (run to waste) substrate is continuously supplied with fresh nutrients, while the old is removed from the substrate by the drainage system. In a closed or re-circulating system the nutrients aren’t removed by the drainage system, it is collected and supplied to the plants again. This is particularly useful if no substrate is being used in cultivation or if the substrate retains relatively little moisture (baked clay pebbles and perlite).

It is very important in hydroponic cultivation systems that the nutrient solution contains all the necessary elements that the plant needs in the correct proportions. The most suitable type of system depends on the grower’s preference and experience. Nutrient Solution Mineral composition of the nutrient Content of the nutrient reservoir Acidity of the nutrient (pH) Nutrient strength (EC) Temperature (water and air) Water quality The nutrient reservoir in recirculating systems must be checked regularly and topped up, or renewed, when necessary. This is necessary to prevent shortages and build-ups of salts. The frequency with which the solution has to be renewed depends on how inten-sive the cultivation process is and the size of the nutrient reser-voir. The nutrient reservoir must contain at least 5 liters per plant. The more nutrient there is available for the plants, the smaller any fluctuations in the pH and EC will be.

Under normal circumstances the nutrient should be renewed every 7 to 14 days. If the nutrient is not renewed in time, the desired balance between the different nutritional elements will be severely disrupted. Nutritional elements such as calcium, magnesium, sulphate, sodium and chloride will build up first. This can happen without affecting the EC! The elements nitrogen and phosphate will be exhausted first, which can cause shortages. These are visible on the larger leaves, which can turn completely yellow (nitrogen shortage), or will show purple spots (phosphate shortage). Build-ups of sodium and chloride will slow down growth. The nutrient reservoir needs to be regularly topped up to its original level, in between the days on which the nutrient solution is renewed. Start topping up when 25 to 50% of the nutrient solution has been used up. It is best to use a solution that is approximately half as strong as the original nutrient solution. In circumstances where evaporation is a concern, the reservoir is best topped up with tap water. This is the case when the temperature is high and humidity is low, for example. In this way, evaporation can take place easily while the nutrient solution’s EC is prevented from rising. Given the fact that the nutrient solution has to be renewed regularly, this is not, strictly speaking, a sealed system. Reverse osmotic filters can be used to remove build-ups of salts such as sodium and chloride, which will reduce the frequency with which the nutrient solution has to be renewed. EC An EC-meter can measure the concentration of dissolved salts and can also measure the total volume of nutrient elements that are dissolved.

In recirculating systems it is certainly not to be trusted 100%. This is because certain nutritional elements have built up in the nutrient solution, while at the same time others have become diluted. It is advisable to start with an EC that is between 0.8 and 1.0 higher than the EC from the water supply and to gradually raise this as necessary to a maximum of 1.3-1.7 above the water supply’s EC. Keeping a regular check on the nutrient solution’s pH and EC levels and observing the plants is necessary to be able to take the correct action at the correct time. (If necessary), pH fluctuations between 6.2 and 5.2 are perfect. pH Stable pH values are important for optimizing the availability of nutrients for the plants. If we compare run to waste systems, with recirculating growing systems then we will see that the pH value in the latter fluctuates more and should therefore be supervised more carefully. This fluctuation occurs because waste products from the roots directly affect the nutrient solution’s pH value. This influence is, among other things, dependent on the plants’ stage of development, their condition, the nutrient solution’s composition and the water supply. During the growing phase, plants tend to cause the nutrient solution’s pH to rise. This happens because at this stage the roots can excrete relative large quantities of elements that increase the pH. During the flowering phase, the reverse happens: the roots now produce acidic secretions causing the nutrient solution’s pH to fall. To a large extent, the nutrient solution’s composition determines whether or not the roots excrete predominantly alkaline or acidic secretions. By using different nutrient solutions that are customized to the different phases of the crop (vegetative and generative), you ensure that the pH remains as stable as possible.

Benefits of Hydroponic Cultivation

The future lies in locally grown and sold produce, limiting the ‘road miles’ applied to todays food supplies. Whilst export opportunities will occur, the main development will be that smaller niche of locally based growers who will sell to supermarkets or to farmers’ markets, florists, local restaurants or wholesale operations, perhaps even supplying to the consumer direct. This method of growing our food is a more sustainable model than those currently practised. The consumer is becoming increasingly concerned over health issues, environmental issues, even water consumption cost and availability……… these are all drivers for the further development of hydroponic growing techniques. There are 5 forces threatening long term crop and food production in open field situations:

1. Increasing ultraviolet radiation.

2. Decreasing fresh water supplies and water quality.

3. Increasing top soil erosion and soil degradation.

4. Increasing resistance of insect pests and plant diseases to traditional chemical controls.

5. A convergence of natural cycles leading to extreme weather conditions.

Further, open field production is hindered because the grower has no control over the growing environment. The result is that the grower cannot predict yields and is unable to budget effectively. The field grower cannot always ensure adequate aeration of the rootzone during periods of extended rainfall. Hydroponic nutrient solutions can be tailored to the plant’s requirements, whereas in the field there is a tendency to over or under-fertilise. Nutrients in the soil are often fixed as insoluble compounds that are not available to plants and therefore a loss to the grower. Irrigation water in field grown operations cannot be effectively recycled.

Hydroponics can reduce irrigation water usage by 70% to 90% by recycling the run-off water. As water becomes scarce, and important as a resource, the use of hydroponics and other water saving technologies will increase in time. Fungal disease can be significantly reduced through controlled humidity. Hydroponic systems will reduce the amount of exposed moisture in the growing environment. Hydroponics will effectively prevent wetting of the leaf surfaces which, in normal agriculture, provides the fungal spores with the perfect medium to proliferate.

All labour inputs associated with soil management, such as digging and weeding are reduced with hydroponics. The use of Integrated Pest Management (IPM) in protected environments is ideally suited to hydroponic growing techniques, especially when carried out in a protected environment such as a glasshouse or plastic/polythene tunnels. The use of IPM can virtually eliminate the need to use toxic and expensive chemical insecticides. Taking all the above into account, it is easy to see why protecting cropping in general and hydroponics especially is becoming increasingly important.

A hydroponically grown greenhouse plant:

1 Can be protected from increasing and damaging UV radiation.

2 Offers the possibility of safe biological control of insect pests and diseases.

3 Uses Water that is reclaimed and reused.

4 Allows nutrients to be reclaimed, re-balanced and re-used.

5 Can be protected from unpredictable weather patterns.

6 Have a good root system that is not at risk from contaminants and diseases.

7 Make very efficient use of labour, which is increasingly expensive.

8 Can be grown to take full advantage of their genetic potential and produce outstanding crops by using optimum nutrient formulations.

9 Can be producing at times when market prices are highest.

Combine these factors with increasing public concern over food safety, pesticide residues and fungicide use; it is easy to see that the future of crop production favours hydroponic and greenhouse production. Especially so when premium prices can be obtained and the demand is sustainable.

To summarise, the benefits include: - Reduced water consumption – a must for the 21st Century. 90% saving in some instances ! Improved Produce Quality – Hydroponically grown produce is often clean and blemish free and full of flavour. A higher price is therefore achievable. Increased Yields and Growth Rates – Grow more produce in less time ! Longer Shelf Life - Hydroponically grown produce tends to have a longer shelf life. Less labour inputs – All labour associated with soil management, such as digging and weeding, is eliminated. Higher Value Crops – Clean, healthy produce will more likely command premium prices. Extended Growing Season – Grow high value crops out of season or deliver early ! Happier Workers – Many systems can be run at waist height eliminating bending down. Lower Labour Costs – Once established, a hydroponic system uses less labour compared to soil based agriculture for harvesting, growing and planting. Pests and Diseases – any problems are more easily controlled. No Soil – No Problem – It is possible to grow things where it would normally be impossible, i.e. in areas of poor or no soil, in rocky areas, on roof tops or even at the South Pole ! Control – With hydroponics it is simpler to manipulate the crop to maximise growth and yields. Market Control – Create and target new market niches.

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