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 for alkaline cookers and dry millers. High test weight corn takes up less storage space than the same weight of corn with a lower test weight. 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. When sampled and measured at the point of delivery from the farm at a given moisture content, high test weight generally indicates high quality, high percent of horneous (or hard) endosperm, and sound, clean corn. Test weight is positively correlated with true density and reflects kernel hardness and kernel maturity.
Average U.S. Aggregate test weight in 2016 (58.3 lb/bu or 75.0 kg/hl) was higher than 2015 (58.2 lb/bu or 74.9 kg/hl), 2014 (57.6 lb/bu or 74.2 kg/hl), and 5YA (58.1 lb/bu or 74.8 kg/hl).
Average U.S. Aggregate test weight in 2016 was well above the minimum for U.S. No. 1 grade (56 lb/bu).
U.S. Aggregate test weight standard deviation in 2016 (1.22 lb/bu) was higher than 2015 (1.08 lb/bu), but lower than 2014 (1.34 lb/bu) and 5YA (1.33 lb/bu), indicating more variability than 2015, but less than 2014 and 5YA.
The range in values was greater among the 2016 harvest samples (10.4 lb/bu) than 2015 (8.1 lb/bu), but similar to 2014 (10.6 lb/bu).
The 2016 test weight values were distributed with 94.9% of the samples at or above the factor limit for U.S. No. 1 grade (56 lb/bu), compared to 94% in 2015 and 77% in 2014. In the 2016 crop, 99.5% of the samples were above the limit for U.S. No. 2 grade (54 lb/bu), compared to 99% in 2015 and 94% in 2014.
Average test weight was above the limit for U.S. No. 1 grade in all ECAs. The Gulf (58.4 lb/bu) and Southern Rail (58.5 lb/bu) ECAs had the highest average test weights. The Pacific Northwest ECA had the lowest test weight (58.0 lb/bu) in 2016, 2015, 2014, and 5YA.
Although the Pacific Northwest ECA had the lowest test weight in 2016, it had less variability as indicated by its lower standard deviation (1.19 lb/bu), compared to the Gulf (1.24 lb/bu) and Southern Rail (1.22 lb/bu) ECAs.