how to measure the effectiveness of an ammonium fertiliser?

Question

please explain and give an example

Answer 1

You would have to set up 5 as-near-as-identical plants as possible, for example seedlings, in identical compost. Keep one as a control, and make up 4 different concentrations of an ammonium salt, for example, ammonium nitrate. Keep all the plants together, at the same temperature, with the same amount of light, and give them the same amount of liquid. The control will have just water, but the others will have the same volume, but of fertiliser solution.
After a week, measure the height of the plants, and see whether the fertiliser has made them grow any taller.