Why is Maseches Brachos in Seder Zeraim? It just doesn't seem to fit with the theme of agriculture. I've asked around and the only answer I got was because some Brachos are on seeds, but that doesn't sound right. Please cite sources.
From the Rambam's introduction to the Mishna, in my own, loose translation:
When a doctor wants to keep a patient healthy, he first adjusts his diet. Thus, the wise compiler of the Mishna started with B'rachos, adjusting our diet, for no one may eat before saying a b'racha. Then, so as to deal with a complete topic, he spoke of b'rachos in general; and because he would speak of the b'rachos said for "Sh'ma", and saying "Sh'ma" is a mitzva every day, he had to first speak of "Sh'ma" itself, which is thus how he started the Mishna.