What are some things that harm the growth of vegetation?

Question

Things that I could simulate in a science project.

Answer 1

too much water, high soluble salts, high and low pH, low light vs high light, different kinds of light (grow lights vs natural light). You could try soil types, sandy soils vs loamy soils vs hydroponic growing media.

Make sure to germinate way more plants than you need because there is a percentage loss from starting seed.

Answer 2

Water conditions would be a really easy thing to simulate. Have 3 identical plants. Over water, under water, and water just right.

Light would also be very easy in the same way.  

Nitrogen - same project as above but with fertilizer.

Answer 3

Too much CO2 will make it grow fast, but it will be spindly and weak, or even kill it.

Answer 4

remove CO2.  Put the plant in a upside down aqurium.  Have plenty of sun and water.  You can buy or get donated a bottle of N2.  Do the same with excess CO2 and one with plenty of air.