23/10/2019
Feeding and Fertilization of Plants.
In order to optimize the performance of all plants, adequate balanced nutrients must be made available to the plants, whether they be flowers, shrubs, fruit bearing trees or lawns.
Plant food is normally classified into two categories, namely Micro or Macro elements.
MICRO-ELEMENTS (or trace-elements) consist of iron, manganese, zinc, copper, boron and molybdenum. Plants only require small quantities of these elements, most of which are normally present in the garden soil. It is difficult for the untrained to diagnose deficiencies of micro-elements, and should one wish to assess these requirements, soil tests should be done professionally. Care should be exercised when adding micro-elements, as an overdose may be as detrimental as a deficiency.
MACRO-ELEMENTS consist of nitrogen, phosphorus, potassium, calcium, magnesium and sulphur. Plants require large quantities of these elements. A range of standard combinations are produced for different plant types, and care should be exercised in selecting the correct product for the purpose. It should be noted that macro-elements are not more important that micro-elements. Furthermore, an overdose of one element cannot make up for the deficiency of another.
The most important macro-elements are:
NITROGEN (N) which promotes plant growth when properly applied, resulting in lush green foliage. Ammonium sulphate and limestone ammonium nitrate (L A N) are two readily available fertilizers containing nitrogen. Nitrogen is easily leached from the soil and should be replenished at regular intervals. Should the fertilizer come into contact with any part of the plant before absorbing the required quantity of water, such part (root, stem or leaves) will be chemically burned. Care should therefore be taken to prevent an over dosage and to ensure adequate watering after application. Gardeners often fertilize just prior to a rainstorm.
PHOSPHORUS (P) primarily promotes root growth but also contributes to the overall development of plants. It is relatively immobile in the soil and is therefore not easily leached out. As South African soils, especially in coastal areas, generally show a phosphorus deficiency, fertilizers with a high phosphorus content should be used when establishing a new garden or planting shrubs. A single element fertilizer containing only phosphorous is available as Superphosphate. All balanced fertilizers available do however contain some phosphorus.
POTASSIUM (K) works in conjunction with the other elements and promotes tissue and carbohydrate formation. It increases the resistance of plants to disease and enhances the formation of fruit and flowers. When needed, small dosages should be applied regularly for optimum results.
Fertilizer Compounds
Most Fertilizer mixtures consist of combinations of nitrogen (N), phosphorus (P) and potassium (K), in different ratios for different applications.
All Fertilizer mixtures are identified by N:P:K, ratios. A compound described as 2:3:2 (22) contains 2 parts nitrogen, 3 parts of phosphorous and 2 parts of potassium, in 22% available plant food. The latter Figure is indicated between the brackets.
SR on the fertilizer bag indicates that the fertilizer that releases a small, steady amount of nutrients over a course of time.
How much fertilizer must be applied?
On average a single application of fertilizer should be 150g/m2.
From this one can determine the quantity of fertiliser needed for any given area which is to be fertilized by simply multiply the area to be fertilized (in m2) by the factor of 150kg/m2, e.g. an area of 160 m2 requires – 150 g/m2 x 160 m2 = 24,000 grams fertilizer = 24 kg.
The area which can be fertilized by a given quantity of fertilizer can also be calculated e.g. a bag of 50 kg fertilizer can fertilize 50 kg x 1000/150 = 333.3 m2
