There are two basic types of fertilizers: organic and inorganic. Organic fertilizers are derived from living organisms, and it adds texture to the potting soil. Bacteria and fungi in the soil break down organic fertilizer so that the plants can slowly but steadily take up the nutrition from the fertilizer. Inorganic fertilizer, on the other hand, delivers more nutrients more quickly to the plants, but it does not improve the potting soil like organic fertilizers do.
The best organic fertilizers to use include manure, compost, seaweed and worm castings.
Manure. If you choose to use manure in the garden, make sure to either purchase it from your local garden shop or prepare it correctly. Animal manure must be mixed with straw or sawdust and rotted before it is used with container plants, otherwise it will add harmful ammonia to the soil. Manure that has been rotted should have no odor.
Compost. Compost piles in yards are compost of decomposing waste from the kitchen or the garden (when adding). Bacteria breaks down the nutrients and makes it usable for plants (you know bacteria is doing its job if the air around the compost feels warm).
Seaweed. Dried and prepared seaweed is available at some local garden shops, and it contains a lot of potassium, which is beneficial to plants. This is not a balanced fertilizer.
Worm compost. Worm compost from a vermicomposting bin is like composted material, except with the help of worms. Worms will take kitchen waste, such as rotting vegetables, eggshells and coffee grounds, and convert it into “black gold.” Worm castings are easy to create yourself in your balcony garden, beneficial for the environment and produce fantastic results when growing plants.
Inorganic fertilizers are manmade and are chemical additives, such as nitrogen, phosphorus, potassium (the three essential nutrients for plants), calcium, iron, zinc, magnesium and more. Inorganic fertilizers from your local garden shop can come in many different forms, such as solids and liquids. Liquid fertilizers release nutrients quickly, while slow-release pellets or granules can be applied monthly or once a season.
Inorganic fertilizers also created to have varying NPK levels (NPK stands for the following nutrients: nitrogen, phosphorus and potassium). NPK is expressed on fertilizer labels with three numbers separated by colons, such as 4:4:6. If you want better stem or leaf growth, choose a fertilizer with a higher nitrogen level. If your plants need better root growth, then choose one with a higher phosphorous level. If you need nutrients for fruit or flowers, choose a fertilizer with a higher level of potassium. Most gardeners can purchase one balanced fertilizer to use on most of their plants. Some specialized plants, such as roses, bromeliads or other finicky plants, have specific fertilizer types that gardeners can purchase (the fertilizer container will be clearly labeled as such).