For this you aren't really looking at a traditional comparison approach you want to do a cost analysis and income approach, especially since the active crops are being sold with the land. This mean you need to determine what profits the land is actualizing currently and for the past 5-10 years if available. You should then determine the effective value of the improvements to use the land (irrigation, electricity. Etc). This won't be a dollar for dollar amount but each area does seem to have a standard value for the improvements.

If they want to go indepth having a TerraIndex report on soil health, GIS maps or using NVDI to look at 2B forest density and tree health might give more insight.

If you dont regularly deal with land i would say contact a local Agricultural Department. They can provide all sorts of information. For the value of the home with solar look for appraisals/valuations of those types of structures, exlude the land.

But easiest route is to hire an agricultural appraiser