Which group of plants is the control group out of these two?

Question

Group A was fed a balanced application of fertilizer with additional nitrogen.
Group B was grown under identical conditions, except the fertilizer they recieved contained no additional nitrogen.

Which plants represent the control group? Which plants represent the experimental group? What were the independent and dependent variables?

Answer 1

I agree with Bhavi that Group B is the control group (regular fertilizer) and Group A is the experimental group (fertilizer with additional nitrogen).

The variable that is changed is the amount of nitrogen, so that's the independent variable.

The dependent variable will be the result measured or counted -- what happened because of the independent variable. Your description doesn't tell how the groups of plants are supposed to be evaluated, but the dependent variable may be any of these:
-- height of the plants
-- final dry mass of the plants
-- subjective descriptions of the green-ness of the plants
-- mass of seeds or fruits from the plants

... whatever is measured or counted for the results.

Answer 2

Group B is the control.

Group A is the experimental as it contains the additional nitrogen.

Independent as you can control according to how much nitrogen you give them.