[mespe]

Hi - coming from a PhD in agriculture (focus on sustainable ag), graduate level courses are going to be tough to jump into unless you have a strong background in ecology. Most of my grad-level courses assumed years of training in e.g. genetics, soil science and chemistry, plant physiology, ecology, weed science, entomology, etc. Agriculture is a very broad life science field.

That said, if you want a quick primer, "Crop ecology: productivity and management in agricultural systems" is a good primer on most of the basic ecological systems in agriculture. I've read it cover to cover many times.

However, you don't need a grad-level education to farm (believe me, I have been reminded this endlessly) - this is more for people doing research. For applied/actionable specifics for cold climates, your best friend is going to be local crop-extension services (in the US, most land-grants run an extension service). They will have tested techniques for your area and will be able to point you to good resources for farmers, not people researching agriculture.

[mespe]

One last thing - to be a successful farmer has very little to do with growing crops. Take business classes - the rest is relatively easy to figure out.