As for organic verses inorganic types, both have their advantages and disadvantages. Inorganic types are easier to use and we have more control over the content of nutrients in these sources. This allows us to apply our nutrients more accurately. Organic sources are variable in their nutrient content and we have very little control over this. However, organic sources can sometimes be obtained for little or no cost, it adds valuable organic matter to the soil and has some slow release action.
Timing means everything to the efficient use of fertilizer.
As a rule of thumb for all plants, fertilizer needs to be applied when the plant is actively growing. This timing will depend on the specific crop that you are growing. Before applying, know when your crop needs fertilizer and apply it so that the nutrients will be available when the plants need them. Just as I mentioned earlier for determining the type of fertilizer to use, you will need to know your crop needs as well as the amount of nutrients available in the soil, to determine the amount of fertilizer to apply. Find out what your crop needs and have your soil tested.