Harvest v3

treeSpacing=2
deepCount=9
wideCount=14
minFuel=30
fuelSpot=1
woodSpot=2
saplingSpot=3
fertilizerSpot=4
sapBackup=16

function plantTree()
  turtle.select(saplingSpot)
  turtle.placeDown()
  if turtle.getItemCount(saplingSpot)==0 then
    turtle.select(sapBackup)
    turtle.transferTo(saplingSpot,turtle.getItemCount(sapBackup))
  end
  turtle.select(woodSpot)
end

function checkFuel()
  if turtle.getFuelLevel() < minFuel then
    turtle.select(fuelSpot)
    turtle.refuel(1)
  end
end

function chopTree()
  turtle.dig()
  turtle.forward()
  turtle.digDown()
  plantTree()
  while turtle.compareUp() do
    turtle.digUp()
    turtle.up()
  end
  while turtle.down() do end
  turtle.forward()
end

function fertilizeTree()
  turtle.down()
  turtle.select(fertilizerSpot)
  turtle.place()
  turtle.select(woodSpot)
  turtle.up()
end

function nextColumn(currentColumn)
  if currentColumn % 2 == 1 then
    turtle.turnRight()
    turtle.forward()
    turtle.forward()
    turtle.forward()
    turtle.turnRight()
  else
    turtle.turnLeft()
    turtle.forward()
    turtle.forward()
    turtle.forward()
    turtle.turnLeft()
  end
end

function dumpExtra()
  for slot=5,15 do
    turtle.select(slot)
    turtle.drop()
  end
end

function dumpLogs()
  dumpExtra()
  turtle.select(woodSpot)
  turtle.drop(turtle.getItemCount(woodSpot)-1)
end

function resetToStart()
  turtle.select(fuelSpot)
  turtle.refuel(2)
  turtle.turnRight()
  while turtle.forward() do end
  turtle.select(saplingSpot)
  turtle.suck()
  turtle.select(sapBackup)
  turtle.suck()
  dumpExtra()
  turtle.turnLeft()
  turtle.select(fuelSpot)
  turtle.suck()
  dumpExtra()
  turnAround()
end

function turnAround()
  turtle.turnLeft()
  turtle.turnLeft()
end

function tryChop()
  if turtle.compare() then
    chopTree()
  else
    fertilizeTree()
    if turtle.compare() then
        chopTree()
    else -- if fertilize didn't spawn a tree for some reason, skip this and go to next tree
        turtle.forward()
        turtle.forward()
    end
  end
end

--while true do
  checkFuel()
  turtle.up()
  for j=1,wideCount do
    tryChop()
    for i=1,deepCount-1 do
      checkFuel()
      turtle.select(woodSpot)
      for s=1,treeSpacing-1 do
        turtle.forward()
      end

      tryChop()

    end

    if wideCount~=j then
      nextColumn(j)
    end
  end
  turtle.down()
  dumpLogs()
  resetToStart()
--end