Are you able to get fresh manure? If so, you can plan to have 'well-rotted' manure for your plants by keeping it in a heap for a year or so to rot down; or layering it in your compost heap; or putting it into trenches where you will be growing spuds (they will tolerate fresh manure). If your manure is full of wood chippings or sawdust, it might take longer than straw to get to 'well rotted' stage, but you will be able to tell by the sniff 'n crumble test as already suggested. I have successfully laid fresh manure on 'set aside' parts of the lottie before covering with black plastic for a few months, and the worms seemed to love it.