Yes. Like everything in love, there is a downside. The problem with them is they invest in futures and have to roll them. Sometimes that helps if the term structure is in backwardation (current market price is higher than the futures price) and sometimes it hurts if the term structure is in contango (mp is lower than futures price). The are etfs for a lot of stuff. If you want to see the negative impact, look at a 10yr chart for UNG (nat gas, which is the basis for most fertilizer products). DBA is the big Grains etf. If you bought in 2012 at the last price spike you would still be in the red.
I guess my point is that investing in commodities is generally a bad idea because they aren’t investments. If you find a trend following fund that trades them, the results might be different.