Spreading, with traders buying corn and selling soybeans, limited losses in corn.
Benchmark March futures ended down 1/2 cent at $3.47 a bushel after matching Friday's contract low of $3.46-1/2 earlier in the session. May through September and March 2019 also matched their previous contract lows, while May 2019 futures notched a new low.
Weekend rains in Argentina brought relief to parched farm belt and allowed planting to resume in most of the affected areas.
Speculation that the US Department of Agriculture would raise its 2017 US corn production estimate in its next monthly report in January also hung over the market. Private analytics firm Informa Economics raised its corn forecast on Friday.
The supplement to the CFTC's weekly commitments report showed large speculators expanded their net short position in CBOT corn by about 36,000 contracts in the week to Dec. 12, to 238,065 lots.