Re: Partition With Land Improvements
A partition case is a two-step process. In the first phase, the court will adjudicate the plaintiff's right to force a partition and determine whether it should be by physical division (very uncommon nowadays due to subdivision laws and the smaller and highly improved nature of most parcels) or by sale and division of the net proceeds. In the second phase, usually handled by a court-appointed referee, the economics of the sale and division are worked out. A great majority of partition cases are settled prior to final judgment, and usually before the property is ever put on the market. There are exceptions.
One of the first factual matters a court or referee would inquire into would be whether the co-owners had a contract, written, oral or implied, that modifies the usual application of principles of law and equity, or whether either co-owner intended to make a gift to the other.
If these matters are resolved in the negative, the court or referee should divide the net proceeds according to equitable ownership of title, usually but not always per the deed, after making adjustments for unequal contributions for mortgage payments, taxes, insurance, maintenance and improvements.
Therefore, I would say your partner will probably get reimbursed for his costs, perhaps without interest, but will not get the current fair market value of the mature vineyard...that's probably your best-case scenario unless there is a gift or contract giving you a better result.
The court or referee will be concerned about getting best value overall, and if a buy-out of one co-owner by the other is offered and the price looks attractive, the court probably has the equitable power to oblige the offeree to sell. I will research this and get back to you.
I have just successfully concluded two partition cases in Sonoma County and would be pleased to consult with you and provide references. I also co-own a small vineyard.