Can Land/Property Value % For Depreciation?

[Brian G.]

Is it possible to change the depreciation write off amount for tax purposes on a rental property? I was advised to use a 40% land 60% structure ratio applied to the purchase to figure out my depreciation amount (which I have done for 5 years) however I noticed that the county assessor ratio is more like 25% land 75% structure which if used would allow me to increase my depreciation write off by $700 and shelter more income going forward. Can I just change the ratio going forward? Is it wise to amend my tax returns or simply use a the different ratio starting with my 2016 tax returns?