Contrary to what many suppose, hydroponics didn’t begin with the Hanging Gardens of Babylon – there were no compound chemicals available then and, at best, the Hanging Gardens were a series of cleverly constructed water channels down which the water flowed thus watering all the plants in soil-based systems from top to bottom. Rather, it began in the USA during the 1930s as an outgrowth of the culture techniques used by plant physiologists in plant nutrition experiments in that country.
What is hydroponics?
Its name gives us the sense that hydroponics means to work in water – hydro being the Greek for water, and ponos, work. In a nutshell, the basic difference between hydroponics and traditional soil-based agriculture lies in the fact that in hydroponics the nutrient food for the plants comes from water-soluble nutrients, whereas in agriculture the nutrients come from the soil. So, in hydroponics there is no soil – hydroponics can thus be said to be the growing of plants in nutrient solutions (rather than just water) with or without sand, gravel or other inert media to provide mechanical support.
Having established that fact, one might be tempted to assume that hydroponics is a much simpler way of growing plants than growing in the soil, but this is not totally true. Hydroponics is a meld of chemical engineering and agriculture together and, apart from nutrition, other aspects such as pest and diseases, and the preferences of the plant for more or less light remain the same.
Plant nutrition in hydroponics
Plant nutrition in hydroponics is based upon the premise that all the nutrients that are required for the plant’s growth throughout its life cycle will be supplied in the same proportions that the plant will take up. Developmental science has established that there are 16 different elements that need to be supplied to the plant to maintain growth, development and survival, or put another way, for foliar development, flowering and fruiting. These elements are divided into six macronutrients (where the minerals are absorbed in large quantities), seven micronutrients (where the minerals are absorbed in minute quantities) and three gases.
Minerals are measured in parts per million (ppm) and these are expressed in grams per million cubic centimetres of water. 1m ccs of water is 1 litre so ppms = g/l in the case of macronutrients and milligrams (one thousandth of a gram) per 1m ccs water in the case of micro nutrients or mg/l. Developmental science has established certain bandwidths within which the minerals should fall and they are broadly as follows:
Nitrogen (N): 100-450
Phosphorous (P): 10-100
Potassium (K): 100-750
Magnesium (Mg): 20-95
Calcium (Ca): 70-350
Sulphur (S): 20-250
Iron (Fe): 1-6
Manganese (Mn): 0.8-4
Boron (B): 0.3-0.8
Zinc (Zn ): 0.2-0.5
Molybdenum (Mo): 0.05-0.2
Copper (Cu): 0.05-0.1
Chlorine (Cl): 0.01-0.02
The reason for such precision in the balance of nutrients is to avoid toxicity or deficiency in the nutrient mix.
Thus, contrary to what occurs in soil, the plants are supplied in just the correct proportions that they need resulting in perfectly balanced nutrition, the exact requirements of the plant resulting in optimal growth and high quality produce. If the produce is perfect, then so are the availability of vitamins and minerals also at their maximum. In soil and organic growing, the plant nutrients are not perfectly balanced often resulting in poor nutrition and slow growth. Yields are reduced and growth is stunted with consequent attacks by pests and diseases as they always attack a weak plant first.
Soil versus hydroponics
When growing in soil, farmers must have their soils analysed to establish what minerals are missing, and add lime to them to balance the pH level and fertilisers to fill in the missing minerals. Completely balanced nutrient levels are not always possible when farming in soil.
Most fertiliser companies supply their nutrient mixes in the form of a cocktail or blend of nutrients containing all the minerals except Calcium Nitrate which is supplied separately. This is to prevent the Calcium and Sulphur reacting together and forming Calcium Sulphate which sets up like epoxy when mixed together in concentrated form.
pH measures the number of hydrogen ions present in a solution and is important in hydroponics because the minerals are absorbed by the plant more readily when the pH is between 5.5 and 6.0 (7.0 is neutral). A hydroponic enthusiast should get a handheld pH and EC meter combined – Hanna instruments make a good one.
It’s important, before starting a hydroponic venture, to get a proper education in hydroponics. This will save you a lot of money and prevent you from making costly mistakes. DaisyFresh holds monthly two-day hydroponics courses in Camperdown, outside Durban. Contact us for further information.