1- Take seedlings of the same parent plant and grow them to get genetically identical plants of the same age and size.
2- Place plants in equal amounts of nitrate ion solution, made by adding 200 cm3 of water to 50 ppm of nitrate ions, keeping all other minerals constant.
3- Allow the plants to grow at 25 degree Celsius at room temperature near a light source of a 250 W light bulb for 4 weeks. Keep on adding distilled water when required.
4- Measure the growth of the plant by counting the number of leaves formed. Repeat the same experiment with different concentrations of nitrates, 100, 150, 200 and 250 ppm.
5- Compare the number of leaves for each concentration. Repeat the whole experiment to get more reliable and valid results. Record the data and plot the graph.
Okay fine, this is how we compare the effects of different concentrations of nitrate ions. My question is, how do we compare the effects of different minerals?