Rice Dairy flagged the potential for a "sharp increase" in corn prices, assuming US yields follow the historical pattern of following a record season with a significantly lower result the following year.
The Chicago-based broker, which has a large number of dairy industry clients, urged milk producers to cover some of their forward corn needs, flagging a potential risk of prices of the grain topping $4.50 a bushel this summer.
That is well above the $3.88 ¾ a bushel at which Chicago's September futures contract was trading at on Wednesday.
"Given the current tight margins in the dairy industry, the strong possibility of production volatility returning to the US corn crop... has us concerned about a sharp increase in corn costs in feed rations the second half of 2015," said Jerry Gidel, chief feed grains analyst at Rice Dairy.
The caution reflected widespread ideas that US farmers will not only cut sowings of corn this year, with Rice Dairy factoring in a drop in plantings of 2.1m acres to 88.5m acres, but that they will achieve weaker yields too.
Years of record corn yields, year-after result, and (% change)
1992: 131.5 bushels per acre, 100.7 bushels per acre, (-23%)
1994: 138.6 bushels per acre, 113.5 bushels per acre, (-18.1%)
2004: 160.3 bushels per acre, 147.9 bushels per acre, (-7.7%)
2009: 164.7 bushels per acre, 152.8 bushels per acre, (-7.2%)
2014: 171.0 bushels per acre
Sources: USDA, Agrimoney.com
"An interesting pattern has developed since 1990," Mr Gidel said, noting that on the four occasions that US corn yields had set a record since then, yields had dropped "sharply" the following season.
After the past two record yield years, of 2005 and 2010, "the combination of a record crop pulling a high percentage of the nutrients from the ground, and producers reducing inputs to save money, has cut the US corn yield by 12 bushels per acre".
Even steeper drops were seen after the record harvests of 1992 and 1994, of 31 bushels per acre and 25 bushels per acre respectively.
It is a trend that has been noted by New York-based broker Jefferies too, which also foresaw a potential drop in yield this year from the record 171.0 bushels per acre achieved in 2014.
"Farmer income has peaked and expected to drop significantly," said Shawn McCambridge, senior grains analyst at Jefferies.
"Famers will be looking for ways to reduce production costs, including cheaper seeds, less for chemicals/fertilizer, and fewer seeds per acre."
After the past four years that a record yield was set, "yields dropped in each season that followed.
"Unless weather conditions are ideal across all corn producing areas of the country, 2015-16 could make it five-for-five in our view."
The comments come amid growing talk of US farmers, faced with lower crop prices, cutting back on fertilizer use, particularly of nitrogen, which is a key requirement for boosting corn yields.
US farmgate corn price during season with record yield, and (year-on-year change)
1992-93: $2.07 a bushel, (-12.7%)
1994-95: $2.26 a bushel, (-9.6%)
2004-05: $2.06 a bushel, (-14.9%)
2009-10: $3.55 a bushel, (-12.6%)
2014-15: $3.70 a bushel, (-17.0%)
Sources: USDA, Agrimoney.com
Richard Feltes, at RJ O'Brien, said that talk of "reduced 2015 US corn fertilizer rates", which tallied with the broker's own intelligence from western Corn Belt contacts, suggested "an even lower US corn yield nationally", below the 166.8 bushels per acre forecast by the USDA, and the 164.0 bushels per acre expected by the University of Illinois.
In fact, the farmgate US corn price for 2014-15 is forecast by the US Department of Agriculture, at $3.70 a bushel at the midpoint of the range, falling by 17.0% year on year – bigger drops than seen after the record harvests in 1992, 1994, 2004 and 2009 undermined values.
Jerry Gidel has pencilled in a yield this year of 162.0 bushels per acre, a figure which, given growing demand, both this year and last, could be insufficient to prevent stocks falling back below 1bn bushels at the close of 2015-16, on Rice Dairy estimates.
"Given this year's low prices, US domestic demand should also expand by 1-2% because of higher livestock numbers and solid ethanol demand," Mr Gidel said.