Here is a study that says that ag-related businesses did better than the S&P 500 the last few years.
http://www.farmdocdaily.illinois.edu/2011/04/performance_of_publicallytrade.html
Summary
As a group, the market values of publically traded firms within the AgIndex exceeded those of S&P 500 in the last five years. Since 2008, market value changes have been larger for AgIndex than for the S&P 500. Like crop farms, many agricultural firms have performed well in the period of higher commodity prices.
Market values varied across sectors. Fertilizer, equipment, and seed & genetic sectors had large increases in market values. These firms supply products to farmers, who have generally had above-average incomes. Farm’s having above average incomes likely led to higher demand for fertilizer, equipment, and seed & genetic sectors. The sector that had the lowest market value increase from 2007 was the first processor sector. This sector purchases inputs from grain farms and higher commodity prices may have played a role in lower market values.
Issued by Clay Kramer and Gary Schnitkey
Department of Agricultural and Consumer Economics
University of Illinois
