Harvest and the Limits of Land Value

Can Harvest propel a land beyond value 9 or is such a bountiful place beyond improvement even by such divine magic? If so, is the limit of magically improved land value 11? This has the added benifit of potentially giving all negative demand modifiers. Similarly, can multiple harvest spells stack with each other? Can a 3 value wasteland be turned into a 9 value paradise?

I'd be very interested in knowing that myself.  Our party has created three adjacent domains, and one of our number is an 11th level Divine caster.