[Solved]What am I supposed put in the NBTTagCompound Field for a compressor recipe?

I am working on making a compressor recipe and am only having one problem: It requires that I add an NBTTagCompound field between the input and output, and I don't know what to put there. Here is the current code:

Recipes.compressor.addRecipe(dirtStack,  NBTTagCompound, darkDirtStack);

Note: I am using the most recent IC2 experimental API, if that changes anything.

Sorry if I am just not doing it right, but when I entered null into the field, I got this error message for it:

The method addRecipe(IRecipeInput, NBTTagCompound, ItemStack...) in the type IMachineRecipeManager is not applicable for the arguments (ItemStack, null, ItemStack)

One final question(Sorry, but I can't find it elsewhere):
In the code

IRecipeInput dirtStack = new WHATGOESHERE(Block.dirt);

, what goes in the spot labeled 'WHATGOESHERE'?

Thanks! That was exactly what I needed.