Yes, you can enter the land apart from the building on the sale screen. However, this will fail to show the difference in the land price in 2012 and now. Also, you will have been depreciating the property based on the amount including land. There is no way to fix that apart from using Form 3115, which TurboTax does not support.

Unfortunately the depreciation recapture is "allowed or allowable" meaning even if you never depreciated it, you would still have to recapture the depreciation. Depreciation taken would be on line 18 of Schedule E.

One solution is to elect an accounting method change and file a Form 3115 in the current year and take the  prior depreciation as a section 481(a) adjustment. [land  value is separated, land is not depreciated]

Below are the IRS links related to the change in accounting method. TurboTax does not have that form.

May be these will help

Form 3115, Application for Change in Accounting Method

http://www.irs.gov/uac/Form-3115,-Application-for-Change-in-Accounting-Method

Instructions for Form 3115 (03/2012) 

http://www.irs.gov/instructions/i3115/index.html

Form 3115,

http://www.irs.gov/file_source/pub/irs-pdf/f3115.pdf