Fertilizers are broken into two broad categories, organic and inorganic (or artificial/ chemical). Both are useful and have their advantages and disadvantages if used correctly.
Some basics: Plant nutrient requirements are divided into Basic nutrients, Macro-Elements, and Micro-Elements or Trace Elements.
Basic elements and their atomic symbols
Carbon (C)
Oxygen (O)
Hydrogen (H)
These are obtained from water and air
Primary/ Macro-elements and their atomic symbols
Nitrogen (N)
Phosphorus (P)
Potassium (K)
These are the NPK or big three that everyone always references in terms of fertilizers
Secondary/ Micro-elements and their atomic symbols
Calcium (Ca)
Boron (B)
Zinc (Zn)
Nickel (Ni)
Magnesium (Mn)
Iron (Fe)
Copper (Cu)
Molybdenum (Mo)
Chlorine (Cl)
Sulphur (S)
Sodium (Na)
The lack of these micro-elements causes what is called trace element deficiencies. The "complete" list of these elements varies depending on who you talk to and which references you consult
All fertilizers irrespective of source have to be diluted in water. This is referred to as the "soil solution" which is the water contained in the soil along with any chemicals dissolved in it. The elements have to be in solution in order to be absorbed by the root system.
Fertilizers should not be confused with “growth stimulants” these are not one and the same thing, stimulants, stimulate growth but do not provide nutrition.
Organic Fertilizers (also sometimes called soil conditioners), are products that are derived from an organic source, products such as manure, chicken manure, compost, and decaying leaves are all considered an organic fertilizers as they contain nutrients that are released and made available for the plant root system to absorb.
In general, organic fertilizers take longer for their effects to become apparent in the plant; the nutrients are locked up in molecular forms which have to undergo decomposition in order to first release them and in some cases convert them to forms that are water soluble so that they can be absorbed.
This “slow release” action has the advantage of not causing sudden changes to the soil chemistry (such as the pH) which could adversely affect the plants. The other advantage of organics is that they have structure in the form of fiber which adds to the structure of the soil over time, an added benefit is organics have a large surface area in the soil, which provided numerous “points of attachment” for nutrients to be exposed to the roots, and are not quickly leached from the soil by watering. As organic fertilizers are sourced from organic components their formulation is variable, although most companies will try to include the composition on the packaging.
One big advantage to using organic fertilizers is that they almost always come with a host of beneficial biological content (bacteria and fungi) which all contribute to the soil ecology, improving the breakdown of the organic matter and improving nutrient uptake by the plant.
Chemical Fertilizers are produced artificially or are derived as the by-product to a chemical process.
They lack the structure that organics have and dissolve entirely and quickly in water and are therefore rapidly leached through the soil by water over a few months - this depends on the structure of the soil and also how much organic content it has as these nutrients can attach themselves to the organic particle and released over a longer period.
As chemical fertilizers dissolve quickly in water and are mainly in the correct chemical formulation for plant use, they are quickly absorbed into the plant and their observable effects are a lot faster.
Some fertilizers can even be diluted in water (fully water soluble) and applied as a foliar spray, which is absorbed directly into the leaves.
A very important disadvantage is they have an almost immediate effect on the soil chemistry, this means they can change the pH of soil dramatically within a few short hours – and if you have applied too much, the change in pH can damage the root system of the plant and even kill it.
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