[dice]

[fish emulsion]
The only problem that I see with using fish emulsion is
that it takes a lot of it to get that initial nitrogen charge
into the bales.

Figure for each cup of ammonium nitrate that he uses
(34% nitrogen), you would need to use 7 cups of undiluted
fish emulsion (5% nitrogen, if it is the usual 5-1-1 Alaska
Fish Fertilizer). You would of course dilute the fish emulsion
enough to make it pour easily and soak into the bale, but that
is really how much you need. The bacteria trying to breakdown
that high-carbon wheat straw will consume the usual
2 tablespoons of fish emulsion in a gallon of water in a
heartbeat, more-or-less.

A couple of handfuls of sulfate of ammonia might do it,
though (very inexpensive, dissolves easily, etc). It is
an acidifier, but the bacteria and fungi inside the straw
bale are basically making compost at a rapid rate, which
tends to even out low and high pH components of what
they are eating, moving the end result toward neutral
pH. I would not use sulfate of ammonia in my garden beds,
because it kills earthworms, but that should not be a big deal
in a straw bale, which does not have any earthworms to start
with. By the time the worms discover it and the internal
temperature drops enough for them to tolerate, the bacteria
will likely have eaten most if not all of the sulfate of ammonia.