stimulate, simulate

Stimulate or stimulate means to invigorate or incite to action or effort--
Some economists want to lower the interest rate to stimulate home buying.
Children may have difficulty concentrating if their video games stimulate them too much.

Simulate or simulate means to pretend or to feign; to take on the appearance of--
This robot was programmed to simulate human speech.
This is meant to simulate a tropical garden; some of it is plastic.

Now that you know that, you can say--
"We hope to use this program to simulate what will happen if we use fertilizer to stimulate growth."

Note--"stimulate" is a verb ( action word ), with all of then usual verb forms--
I stimulate; you stimulate; he stimulates; we are stimulating. Yesterday we stimulated.
"Stimulation" is a noun ( thing or idea ) form of "stimulate"--
This may be too much stimulation for the children.
"Stimulant" is something used to produce energy or to invigorate--
The caffeine in coffee and tea is a commonly used stimulant.
Note # 2--"simulate" is also a verb ( action word ), with all of the usual verb forms--
I simulate; you simulate; he simulates; we simulate; everyone is simulating.
Yesterday we simulated. Tomorrow we will simulate.
"Simulation" is a noun ( thing or idea ) form of "simulate"--
This isn't real; it's a simulation.
Note # 3--not to be confused with "assimilate", meaning to absorb or incorporate, physiaclly or culturally--
It takes time for the body to assimilate the food we have eaten.
"Assimilation" is the noun ( thing or idea ) form of "assimilate". "Assimilation" means absorption or incorporaton--
Most immigrants become Americans through assimilation.