How does fertilization work naturally?(in a system-type way)

[Tideo]

I was wondering...

1.When a plant dies it returns various nutrients to the soil right? And other plants can reuse it?

2.Does that mean that the soil become more fertile over time? Since it would gradually build up? Since the fruits and the plant will return to the soil.

if not then why?

3.If there is a buildup then if people eat the fruits of the plant would that "buildup" be canceled out?

4.If there is a "build up" of nutrients and people eating the fruits will be equal to the amount of nutrients going into the soil how could we learn whats a good "system"

Like how much we can eat. While still giving enough nutrients to the soil.


I hope these questions aren't confusing =\ (this isn't homework) i hope i posted in the right section...

[JackBean]

well, the death plant is usually decomposed (as other death organisms) by many bacteria, fungi, and some animals. However, for the balance, you have to consider also the animals of course.
It probably does not become more fertile, but rather builds up in volume.