B. Moisture

Moisture content is reported on official grade certificates, and maximum moisture content is usually specified in the contract. However, moisture does not determine which numerical grade will be assigned to the sample. Moisture content is important because it affects the amount of dry matter being sold and purchased. Moisture content is also an indicator of whether a need exists for drying, has potential implications for storability, and affects test weight. Higher moisture content at harvest increases the chance of kernel damage during harvesting and drying. Moisture content and the amount of drying required will also affect stress cracks, breakage, and germination. Extremely wet grain may be a precursor to high mold damage later in storage or transport. While the weather during the growing season affects yield, grain composition, and the development of the grain kernels, grain harvest moisture is influenced largely by crop maturation, the timing of harvest, and harvest weather conditions. General moisture storage guidelines suggest that 14% is the maximum moisture content for storage up to 6 to 12 months for good quality, clean corn under aerated storage under typical U.S. corn-belt conditions; and 13% or lower moisture content is recommended for storage of more than one year[1].


  • The average U.S. Aggregate moisture content recorded at the elevator in the 2016 samples was 16.1%, which was higher than 2015 (15.7%), lower than 2014 (16.6%), and the same as 5YA (16.1%).

  • U.S. Aggregate moisture standard deviation in 2016 (1.47%) was lower than in 2015 (1.53%), 2014 (1.84%), and 5YA (1.78%), indicating less variability in the 2016 samples than in prior years.

  • The range in moisture content values in 2016 (11.2 to 23.7%) was the same as 2015 (11.0 to 23.5%), but less than 2014 (10.9 to 29.9%).

  • The 2016 moisture values were distributed with 33.1%[1] of the samples containing 15% or less moisture. Fifteen percent is the base moisture used by most elevators for discounts and is a level considered safe for storage for short periods during low wintertime temperatures. There were more high moisture samples in the 2016 crop than in the 2015 crop, with 28.4% of the samples containing more than 17% moisture, compared to 19% in 2015 and 37% in 2014. This distribution indicates more drying will be required in 2016 than in 2015, but less than in 2014.

  • In the 2016 crop, 12.5% of the samples contained 14% or less moisture compared to 19.8% in 2015 and 12.4% in 2014. Moisture content values of 14% and below are generally considered a safe level for longer–term storage and transport.

  • The average moisture content for corn from the Gulf ECA (16.2%) was higher than the Pacific Northwest (15.9%) and the Southern Rail (15.7%) ECAs.

  • Average moisture levels for the Gulf ECA were highest or tied for highest among all ECAs for 2016, 2015, 2014, and 5YA. Samples from the Gulf usually contain higher moisture content values as a result of weather and harvest conditions.

  • Because of higher moistures in 2016 than in 2015, and higher total damage levels in 2016 than in previous years, care should be taken to monitor and maintain moisture levels sufficiently low to prevent possible future mold growth.

    [1]MWPS-13. 1988. Grain drying, handling and storage handbook. Midwest Plan Service No. 13. Iowa State University, Ames, IA 50011.

    [2]The pie chart and the histogram show that 33.2% and 33.1%, respectively, of the samples contained 15% or less moisture. This difference is solely due to rounding.