Plants too can suffer from hunger, even at the same time as they have an excess of nutrients. Shortages and surpluses are reflected in how the plant looks and ‘behaves’. In any case, all plants need light, air, nutrients, and water.
Having sufficient light gives the plant the energy, with the help of carbon dioxide (CO2), to make the substances it needs for a good development. The plant gets the other necessary nutrients with the aid of its roots out of the medium (coco, soil, rock wool, etc.) and transports them to other parts of the plant.
Let’s assume the temperature is right (24-27°C), the humidity is within the right parameters and there is plenty of light and ventilation. For completeness: insufficient lighting is expressed by the plants stretching towards the light, lengthening as they do so, the distance between the nodes becoming ever greater, and the plants take on a slender, lanky look. Possible cause: bulbs too old or too few Watts given off, or the lamps are hanging too high.
A shortage of carbon dioxide is rare, and is always the result of insufficient air circulation. So if you haven’t got them already, get your hands on a couple of ventilators and ensure your air circulation is up to scratch.
Thus, although many factors may be important, in relation to the nutritional aspects it is most important to keep a close eye on the pH of the medium and the feed water! Depending on the medium, the pH must have a value that lies between 5.5 and 6.2. The pH is after all one of the most important factors in the uptake of necessary nutrients.
In principle there are two situations: not enough or too much of a particular nutritional compound. The ideal situation is where there is precisely enough of everything for the plant. A shortage of nutrients generally shows in the plant as yellowing leaves, while too much nutrient manifests as both exaggerated green leaves and as burnt leaf tips. A shortage of nutrients in the medium can be remedied by adding extra nutrients, available in a variety of forms: liquid, granules, powder, etc. An excess of nutrient is (sometimes) fixable by flushing the medium with water.
There are two broad groups of nutrient: major and trace elements. Both groups need to be available in sufficient amounts in order for the plant to be able to grow optimally. The major elements are the most necessary, and without them, adding extra trace elements makes no sense.
To finish the section, here are a few terms and facts. Shortages or surpluses can cause a whole range of phenomena that we can categorize into two terms. Necrosis is the dying of tissue and is irreversible. Chlorosis is a term we use to describe a colouration that occurs as a result of a shortage of chlorophyll (the stuff that makes leaves green). Chlorosis is (to a certain degree) reversible by the application of the nutrients that are lacking. For a first diagnosis it is important to know that the symptoms of a deficiency are first visible both at the bottom and towards the top of the plant and this is dependent on the mobility capacity of a (deficient) nutrient. A shortage of mobile nutrients (N, P, K, Mg) initially causes a problem in the lower plant. A shortage of less or non-mobile nutrients (Mn, Zn, Ca, S, Fe) manifests first in the upper parts of the plant on the young leaves and/or growth tips.