Water soluble fertilizers are fertilizers that can be dissolved in water and added or leached out of the soil easily. With water soluble fertilizers it is easy to control the precise amount of nutrients available to your plants(the control is more exact with soilless mixes).
Soluble fertilizers usually have N-P-K numbers listed on their label. The numbers listed are not always the exact percentages, they are an indication of the smallest percentage that the fertilizer contains of the listed element. The reason for this is that companies do not want their competitors to know the exact amount of nutrients they have in their product, so they list the lowest levels their product might contain to thwart any copying of their secret growing compounds. The N is for nitrogen, the P is for phosphorus and the K is for potassium or potash. Of the 16(12 of which are contained in water soluble fertlizers) known elements necessary for plant life, N-P-K, are the three that are of the most importance and always listed on water soluble fertilizers, in that order(except Eco-Grow, which lists N-K-P). Following N-P-K, calcium(Ca) and magnesium(Mg) are the two, second most important nutrients listed on the label. The rest, iron(Fe), sulfur(S), manganese(Mn), boron(B), molybdenum(Mb), zinc(Zn) and copper(Cu) are trace elements or micro-nutrients.
Nitrogen is the most important of the nutrients. It controls the processes used to make proteins vital to new protoplasm in the cells. Nitrogen is essential to the production of chlorophyll and is responsible for leaf growth, as well as, overall size and vigor.
Phosphorus is necessary for photosynthesis and provides a mechanism for energy transfer within the plant. Phosphorus is associated with overall vigor and is used at it’s highest levels during germination, seedling and the fruiting or flowering stages of growth.
Potassium, or potash, provides the manufacturing and movement of sugars and starches, as well as, growth by cell division. It also increases chlorophyll levels in the foliage and helps regulate the stomata openings so plants make better use of light and air. Potassium is important in all stages of plant growth.
Trace elements are vital to chlorophyll formation and must be present in minute amounts. Little is known about the exact amounts needed. They function mainly as a catalyst to plant’s processes and the utilization of other elements.
The ultimate goal of fertilizing is to supply your plant with the right amount of nutrients, yet, at the same time not toxifying the soil via over-fertilization. Therefore, follow the instructions given on the product label to get the most out of your plant.