Although agriculture has become a popular market to follow, investing in it can be a tricky task. Individual crops tend to behave in a volatile manner. Therefore the best approach for long term investors would be to target broad-based products like MOO and PowerShares DB Agriculture Fund ( DBA). First Trust NASDAQ Global Auto ETF ( CARZ) The First Trust auto ETF could take the spotlight on Friday when auto and truck sales results released. CARZ provides ETF investors with exposure to a unique and previously-unexplored corner of the markets. However, during the fund's opening weeks of trading it has struggled to gain a following. Currently, its average daily volume stands at a paltry 2,000. CARZ remains vulnerable to illiquidity issues and should ultimately be kept at an arm's length. A stronger and more reliable way to target the automobile sector would be through the Fidelity Select Automobile Fund ( FSAVX). Written by Don Dion in Williamstown, Mass.