In a fertilizer experiment, what are the constants

the plant, soil, water, sunlight, anything you’re not changing

Explanation:

i’m guessing you’re testing to see if the fertilizer works? so it should be anything but the fertilizer since you would we testing one with and without fertilizer

 effective nuclear charge increases as electron shielding remains constant. ... The increased distance weakens the nuclear attraction to the outer-most electron, and is easier to remove (requires less energy).

Explanation:

In general, ionization energy increases across a period and decreases down a group. Across a period, effective nuclear charge increases as electron shielding remains constant. ... The increased distance weakens the nuclear attraction to the outer-most electron, and is easier to remove (requires less energy).