Apply the recommended amount, not double the amount. You can either apply the fertilizer and lightly till the soil (<4-in. depth) or apply fertilizer after tilling and use a metal rake to incorporate it.

Christa

So from what I understand, the 1000 sq ft is for that area and mixed up to 4 inches deep.

Even if I till and mix 8 inches deep, I still use the same recommended amount and area.

Yes, the recommended dosage of a soil amendment (lime, sulfur, etc.) or fertilizer is for the given surface area of soil, regardless of depth being worked. Use the same amount even if you till 8 inches deep. The majority of plant roots are going to be growing in the top foot of soil, where oxygen, moisture, and nutrient access is greatest, so will be able to absorb what they need whether it's closer to the surface or not. Plus, even a surface-applied material will eventually be worked-in to soil layers several inches down over time by rainfall and the action of numerous soil-dwelling organisms (insects, isopods, springtails, millipedes, earthworms, moles, etc.) that provide the natural equivalent of roto-tilling as they travel.

Miri