Digging by hand or by spade you are restricted to the length of the blade
i.e. between 6" to 9" depending on the spade.
You must also consider the depth of your top-soil and its condition. Horse
manure is good as it contains straw which will rot to produce humus, blood
and bone meal are slow release fertilisers.
How well you are going to fluff up the soil depends entirely on the type of
the said soil.
"Frogleg" wrote in message
...
On Thu, 4 Dec 2003 22:24:38 -0800, Down Under On The Bucket Farm
wrote:

So my question is... How deep should I till down through this
soil (I will be doing it by hand)? I figure that the need is to
turn over the grass, etc, and fluff up the soil for veggies to
have a good root-pushing environment. I plan on mixing in a bit
of manure and blood-n-bone meal to feed it.

So... How deep to till?

Most veg roots don't need more that 8-10" (there are *some*
exceptions) of fluffy stuff. Fertilizer is good to dig in, but don't
forget compost. That helps a *lot* to keep the dirt fluffy. Good
luck with your dirt!