4-6 inches will work fine and macro critters in the soil will take some deeper. A number of other factors will weigh in, however, such as how raw the stuff is, when you apply/till it and when you plan to plant. Raw manure could fry young seedlings.

tj

Its about as fresh as you can get it. I spread it on top this fall and will let it set until spring. I'd say most of the nitrogen will be gone by then, at least it shouldn't burn the new seeds and plants.

I'm thinking the poo should be down 8 inches or so not just till it in the top 3-4 inches.

You need to be carefull, it's not just the burn factor but fresh manure can be loaded with all kinds of nasty things. It would be best to windroll it and let it cook for a summer, make sure all then pathogens, bacteria, and whatever else the cows were injected with has had a chance to cook off.

That stuff can not only be transfered into your food but you'll be directly exposed to it while your in the garden.

be sure to check out the composting forum, good luck