Agricultural Commodities Bottoming? ASX: QAG

The prices of agricultural commodities such as sugar, wheat, and soybeans have been falling for some time now. This can be seen in the performance of the QAG ETF.

For a number of months now I have been thinking that these commodities cannot go down forever. If this were the case, soybeans, sugar, etc would eventually be free. Could this be a buying opportunity?

QAG ASX price from 2012 to 2017
Source: Google