Subject: What type of fertilizer, organic or inorganic, promotes betterplant growth?

I am planning to do a science project to test, "What type of fertilizer, 
organic or inorganic, promotes betterplant growth?" I am not really sure how to 
set up the experiment because from what ive read, you are not supposed to add 
fertilizer to the soil until the plant has sprouted. The project i have come up 
with is like this:    
I am planting three types of seeds, wheat berries, soy, and lentils. I am 
planting them all in potting soil, and when each plant sprouts, i plan to add 
fertilizer (organic cow manure to some and inorganic plant food (20-20-20) 
toothers) to each plant around once a week. Is this ok? or should my project be 
set up a diffrent way, or maybe fertilizer can be added from the begining? 
Also, what are some things i can look for to see if my plant is growing well, 
besides height and leaf color

Re: What type of fertilizer, organic or inorganic, promotes betterplant growth?