Attached is the link to the Department of Local Government Finance's "Certification of Agricultural Land Base Rate Value for Assessment Year 2012." In it, the Department calculates the income value of agricultural land to be $1,630 per acre based on the "lowest five years of a six year rolling average".
http://www.in.gov/dlgf/files/111230_-_Certification_Letter_-_2012_Agricultural_Land_Base_Rate.pdf
Also, the Department published its supporting documents:
http://www.in.gov/dlgf/files/Reference_Materials_for_2012_Ag_Land_Base_Rate.pdf
