Lower productivity of crops in initial years

[FraGard]

Thinking that some plants take a few years to become productive and it could be important to take this into account in cases such crops are widespread and new land is assigned to them. If one wants to account for lower productivity over a few years, A 'for' loop may be needed (probably not worth it). But maybe one could account for one year of lower productivity, using some production gap directly multiplied with new capacity of land?