Types of fertilizers and their use
Fertilizing the plants is crucial for their proper growth and development. Flowers are notoriously picky about the nutrients of their soil. Quantity and quality of the nutrients are very important, as well as the need for particular nutritious elements during the different stages of plant’s development. In general, young plants are the ones most sensitive towards concentration of nutrients. Through changes in the content, quantity and the schedule according to which we introduce fertilizers, flowers growth could be regulated, the development rate could be increased or decreased, and the proportion between vegetative and generative organs (through which blossom is formed) could be altered. It is known for a fact that fertilization introduces considerable opportunities for the production of plants with abundant blossoms, continuous and intensive flowering and bright coloring. It could also increase the quantity and quality of the corms, bulbs and seeds.
Types of fertilizers
Depending on the objectives we have in mind, we can use different types of fertilizers. There is a great variety in fertilizers and they can be grouped according to different characteristics. Thus we have organic and mineral fertilizers, depending on the compounds present in their nutritious elements; Direct and indirect – depending on the way they work. These can work either as direct sources of nutrients or as indirect ones, by improving the feeding conditions for the plants.
As far as organic fertilizers go, the most widely used ones are manure, worm castings, compost, seaweed, guano, or naturally occurring mineral deposits (e.g. saltpeter). Their influence is both direct and indirect, because they contain almost all nutritious elements and improve the physical, chemical and biological properties of the soil considerably.
In the mineral fertilizers, the nutritious elements are the mineral compounds, therefore they act directly. According to the prevailing element, these fertilizers fall into three categories: nitrogenous, phosphorus and potassium.
They are further subdivided into groups depending on the state of nitrogen in them – nitrate, ammonium, ammonium-nitrate and amid fertilizers.
Nitrogenous fertilizers are also called saltpetre. Here nitrogen is in its nitric state (NO3). The nitrogen content is about 15%. These fertilizers are physiologically alkaline and are suitable for acid soil. Most widely used are potassium nitrate and sodium nitrate.
In ammonium fertilizers the nitrogen is in its ammonium state (NH4). Physiologically, these are acid fertilizers and are used on alkaline soil. For most ammonium fertilizers the nitrogen content is 20-25%. Most widely used are ammonium sulphate and ammonium chloride.
In ammonium-nitrate fertilizers, nitrogen is present in its two absorbable forms – ammonium and nitrate. Most widely used is the ammonium nitrate, or the ammonium saltpetre.The nitrogen content in this fertilizer is greater – between 33-35%.
Usually, the ammonium nitrate is physiologically neutral and can be used on different types of soil. Plants absorb the nitrite nitrogen first , then the ammonium nitrogen, which makes it possible for the ammonium saltpeter to be active, for longer period.
As for the amid fertilizers, urea(carbamide) is the most common one. Characteristic feature of it is that the nitrogen in it is in its organic state, but easily transforms into mineral state. Urea is the most densely concentrated of all solid nitrogen fertilizers. Its nitrogen content is about 46%. Among its specific properties is that it can be absorbed not only through the roots, but through the leaves as well. This fertilizer is a universal one, suitable for all types of plants and soils.
Phosphorus fertilizers fall into categories according to their solubility. Most widely used are the ones that dissolve easily, like the common and the concentrated superphosphate. The phosphorus oxide (P2O5) content in the common phosphate is between 15-20%. The concentrated one contains 45-54% P2O5. Potassium sulphate contains 48% potassium oxide (K2O).
Semi-soluble phosphorus fertilizers are precipitates, thermo-phosphate, coconut flour. The slowly dissolving ones include bone dust and phosphorus dust.
There is no typical classification for the potassium fertilizers. Widely used are potassium chloride and potassium sulphate. Potassium sulphate is a highly concentrated potassium fertilizer, containing 50-60% potassium oxide. Potassium sulphate contains 48% potassium oxide.
The different properties of the mineral fertilizers define the various ways in which they are used in order for the nutritious elements to be fully absorbed and negative reactions such as turning the soil acid or alkaline to be prevented.
- Nitrogenous fertilizers are fast acting and are used to stimulate plants growth.
- Phosphorous fertilizers are slowly soluble. They are used for intensifying blossom growth.
- Potassium fertilizers are easily soluble and are used in the same way as phosphorous fertilizers.
In recent years, a lot of liquid fertilizers have come into use. The proportion between nitrogen N, phosphorus P and potassium K is different i n them. It is noted on the label. The amounts to be used should also be noted on the label. Among the best liquid fertilizers are those containing both micro-elements and vitamins.
We should always take into account the type of plants we are fertilizing and in what stage of development are they. For example, young or small plants need less fertilizing. During the vegetation period, in spring and summer, more fertilizer is required. Weak solutions could be used to fertilize on weekly basis – for example, one year old plants, or older, often situated on the balcony or in a flower bed. As for pot flowers, they are very different from one another and we need to take into account their type and nutritious needs. There are liquid fertilizers for specific groups of plants, like the Orchid, or different ornamental plants, blossoming plants, Bromelia-like flowers, etc.
Remember that before fertilization or nutrition, plants must be watered, so that the chemicals do not affect roots directly. During autumn and winter, fertilizing at home is not recommended.