"On the bearish side, we are forecasting a 13 percent 12-month return in agriculture," said Goldman analysts in a "Commodity Watch" research note on Tuesday.
"This is being driven by the increasing likelihood of a significant rebound in inventories, on the combination of a realized record-large Latin American harvest, already making its way on the export market and helping rebuild depleted inventories, as well as prospects for record large U.S. production."
(Read More: Latin American Hot Spots Lure Investors)
The U.S. Department of Agriculture forecast that 14.1 billion bushels of corn will be harvested in the U.S. this year, well above the previous record of 13.1 billion in 2009. As of Monday however, only 28 percent of the expected crop had been planted.
U.S. farmers achieved one of their most profitable years on record in 2012, with farm commodity prices boosted by a lengthy and severe drought that constrained supply. In April 2013, around half of the country remained in drought, according to the National Oceanic and Atmospheric Administration, down from 65 percent the previous year.
(Read More: Drought Worsens, Scorching Much of the Country)
Corn traded at about $6.50 per bushel on Wednesday, up more than 20 percent from a year ago. However, Goldman Sachs said that only a second major weather shock could keep crop prices at these levels.
"While weather remains key to our outlook, with a large increase in U.S. planting required in coming weeks for this base case scenario to play out, it is important to emphasize that we believe the record-large realized South American harvest and the current weak level of global consumption requires another major weather shock in the U.S. this summer to keep crop prices near their current levels," the analysts wrote.
Despite the very bearish stance on agricultural commodities, Goldman maintained its neutral outlook on commodities overall. It forecast commodity returns of 0.1 percent in the near-term, and 1.6 percent over the next 12 months.
"Later this year, and into 2014, we expect accelerating economic growth to tighten commodity markets more broadly, likely creating better opportunities for investors to benefit from higher roll yields," Goldman Sachs said in the note.
—By CNBC's Katy Barnato
This story was updated to reflect that corn was trading at about $6.50 a bushel on Wednesday.