Test weight (weight per volume) is a measure of bulk density and is often used as a general indicator of overall quality and as a gauge of endosperm hardness to alkaline cookers and dry millers. It reflects kernel hardness and kernel maturity. Test weight is initially impacted by genetic differences in the structure of the kernel. However, it is also affected by moisture content, method of drying, physical damage to the kernel (broken kernels and scuffed surfaces), foreign material in the sample, kernel size, stress during the growing season, and microbiological damage. High test weight at the export point generally indicates high quality, high percent of horneous (or hard) endosperm, and sound, clean corn.
- Average U.S. Aggregate test weight (57.3 lb/bu or 73.7 kg/hl) was lower than 2014/2015 (57.5 lb/bu) and 4YA (57.7 lb/bu), but the same as 2013/2014 (57.3 lb/bu). The average U.S. Aggregate test weight was above the limit for U.S. No. 1 grade (56.0 lb/bu).
- The 2015/2016 export samples had less variation than the 2014/2015 export samples, as indicated by the lower standard deviation (0.77%) compared to 2014/2015 (0.90%). However, the 2015/2016 variation was close to 4YA (0.79%). The range in values was also less than 2014/2015 and 2013/2014.
- Test weight for 95.9% of the samples was at or above the minimum for U.S. No. 1 grade (56 lb/bu), and 100.0% of the samples were at or above the limit for U.S. No. 2 grade (54 lb/bu).
- Test weight at export was lower than at 2015 harvest (58.2 lb/bu or 74.9 kg/hl). Average test weight at export has been consistently lower than at harvest, with 4YA export average (57.7 lb/bu or 74.2 kg/hl) lower than 4YA harvest average (58.1 lb/bu or 74.8 kg/hl).
- The 2015/2016 export samples’ variability (standard deviation of 0.77%) was less than the 2015 harvest samples (1.08%). As corn is commingled moving through the market channel, test weight changes and becomes more uniform, with a lower standard deviation and a smaller range between maximum and minimum values than at harvest. At export, 4YA standard deviation was 0.79% compared to 4YA of 1.39% at harvest.
- Test weight was higher in samples from the Gulf (57.5 lb/bu) and Southern Rail (57.2 lb/bu) ECAs in comparison to samples from the Pacific Northwest ECA (56.8 lb/bu).
- Average test weight of corn for contracts loaded as U.S. No. 2 o/b (57.3 lb/bu) was slightly higher than for those contracts loaded as U.S. No. 3 o/b (57.2 lb/bu). Averages for both contracts were above the limit for U.S. No. 1.