I love learning about agriculture and living off the land!
Could not agree more. It amazing to think how the practice of agriculture allowed the transition to permanent civilization from nomadic tribes.
Agreed!  Our civilization has come a long way!  I teach our kids the basics in case we have to resort back to old methods.
It is always good to teach about the balance of ecosystems and how we can engage with it to steward it and produce food regardless of climate and technology. 
So what do you think is the most important essential needs or methods of agriculture that we must know?
I think the biggest need right now is learning sustainability - the ability to consistently grow without destroying the land.
I could agree more.  But what I meant was more individual need.  I think we all need to know how to grow our own gardens to survive.
I see. Yes, for individual needs I think what is most important is knowing your own climate zone and what will do well there.