I would suggest lost in the woods and if there is room for more forests add those in as we'll. also since borborgymos is your main win condition, you should have some protection for him like lightning greaves or Swiftfoot boots

meh. you kill him and I throw my hand at you is usually good protection

I LOVE IT!!! Some suggestions:

Crop Rotation, Harrow, Expedition Map for tutors and to be able to get land into your graveyard for Life from the Loam and Creeping Renaissance. Vesuva and Thespian's Stage to screw over Legendary Lands. Ghost Quarter, Tectonic Edge for some spot removal of other problem lands.

Also some Manlands wouldn't hurt, IMO, like Dryad Arbor, Raging Ravine, Ghitu Encampment, Mishra's Factory, Inkmoth Nexus, Blinkmoth Nexus, Dread Statuary, Kher Keep,Gargoyle Castle, Hellion Crucible, and Treetop Village. Maybe even Kessig Wolf Run for fun!

wolf run would be fun, but I don't have one yet. And some manlands/destroyerlands wouldn't be bad either.

Many are relatively inexpensive. Manlands survive the many board wipes in EDH. As do Selesnya Keyrune and Gruul Keyrune.

keyrunes are a no, they have too little benefit in a deck like this

I love this deck! It inspired me to create BorBor, LandLand!.

I had also added Knollspine Dragon to my version independently. Its draw/damage capability is insane in this deck and is essentially another win con.

My only problem with this deck is i felt there wasn't enough ramp and draw power to keep throwing land and drawing into Keen Sense or Snake Umbra for win con. you don't really need specific land draw, most plain draw will be land. and the important cards to draw are non-land because it sets up your win con. e.g. Abundance. instead of putting the land in your hand, its better to put it on the battlefield for ramp e.g. Burgeoning or Manabond. then you can fill your hand back with land by mere draw e.g. Wheel of Fortune and Mind's Eye. i know they are a little expensive but i feel are worth the extra bucks for such awesome draw power.

I absolutely love the amount of mana in your deck. I wanted mine to be just as good because you can literally go through the entire deck with Keen Sense or Snake Umbra, but i decided that having more ramp and draw allowed me to get borbor out quicker and win without necessarily having either of those in play.

try some Mulch

mulch is ok, but not nearly as good as Life from the Loam