Requirements for becoming a naturalized citizen

I assume that you mean in the US?
The process is different for every country and then it's also different depending on your original passport.
In the US you need one of the below: (and then fulfill more detailed requirements)
- 5 years of residence
-3 years of residence if your spouse is an US citizen
-serve in the Military (further conditions apply)
- have a parent who is a citizen

The changes to agriculture in the united states since 1900 is that increased mechanization has increased food production, thereby increasing the need for labor. there has been an increased need for higher speeds of food production due the fact that the population in the united states continues to rise.