read this
http://www.garden-counselor-lawn-care.com/fertilizer-numbers.html
it explains NPK ratings (Nitrogen, Phosphorus, Potassium)
youll see numbers on the back of any fert or nute package like this
15-8-9, 14-3-11, 5-8-8
N-Nitrogen content is the first number
P-Phosphorus content is the second
K-Potassium content being the third
there are also micronutrients these are im portant but not so much as the main three
k now that you can read the labels we can move on to which ones
ex. 15-8-8 high in N. Good for vegging
ex. 5-12-9 high in phosporus Good for flowering
ex. 3-6-9 high in potassium Good for flowering
now to organics like fish emultion fert ( i like)
theres many organic ferts that are alot less harsh on the plants
and MG can be a good fert BUT only when it is used properly in moderation its real picky
(this came from Hydroponicsnutrients.com)
These nutrients play many different roles in plants. Here are some of their dominant functions:
o Nitrogen (N)promotes development of new leaves
o Phosphorus (P)aids in root growth and blooming
o Potassium (K)important for disease resistance and aids growth in extreme temperatures
o Sulfur (S)contributes to healthy, dark green color in leaves
o Calcium (Ca)promotes new root and shoot growth
o Magnesium (Mg)chlorophyll, the pigment that gives plants their green color and absorbs sunlight to make food, contains a Mg ion