Agricultural economists are predicting yields for corn and soybeans to break records this year, almost the polar opposite of the scenario from two years ago. In 2012, the U.S. experienced one of the hottest summers on record, which put a major damper in the supply of these two commodities. This year, the summer was relatively mild, creating ideal growing conditions for the two crops.

The expected production has pushed both of these commodities to near four-year lows and has some worried that prices could continue to sink into 2015. Some have even suggested that farmers hold on to their stockpile and attempt to sell it at a higher price down the road.

Wheat is also sitting at a four-year low, as it has its own problems. U.S. demand for wheat has been relatively small, while stockpiles around the world continue to grow. That combination has made it difficult if not impossible for U.S. producers to be competitive in the global space. The expense of shipping the commodity overseas is one of the biggest factors in this equation.

Earlier this month, the U.S. Department of Agriculture cut its forecast for U.S. exports of wheat, while data overseas has shown countries like Egypt opting to purchase their wheat from countries within a closer proximity.

Wheat is also plentiful in U.S. markets, which is only adding to the downward pressure on its price. The chart below displays what the corn, soybean, and wheat ETFs (CORN, SOYB, and WEAT respectively) have done on the year compared to the broad commodities ETF DBC.

The three grains funds started off the year on the right foot, but things quickly went downhill as the summer months rolled around. Investors will want to keep a close eye on how the stockpile situation plays out with these commodities, as any reversal in the current trend could present a nice buying opportunity for these hard assets.

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Disclosure: No positions at time of writing.