- Kernel weight data was collected from hybrid plots across Iowa in 2016-2020.
- Kernel weights for each hybrid at a location were measured in one of two ways:
- A subsample of 100 random kernels, or more, was weighed and corrected to 15% moisture with the moisture data used to calculate the hybrid’s grain yield.
- Multiple stand/ear and kernel counts were performed prior to harvest to provide a reasonably accurate estimate of ears per acre and kernels per ear. This data was divided by the hybrid’s yield at 15% to determine kernels per bushel.
- Both methods have limitations, but hybrid trends were consistent; thus, datasets were combined to increase the number of locations.
- A location average kernel weight was calculated from the average of all hybrids in each plot location.
- To account for environmental differences across locations, kernel weight for each hybrid within a location was calculated as a percentage of the location average. Those percentages were then averaged by hybrid family over all plot locations, as shown in Table 1.
- The standardized kernels per bushel in Table 1 were calculated as 80,000 kernels/bu divided by the average kernel weight percentage to provide a reasonable estimate for kernels/bu by hybrid family. This result is not the actual mean of the observed kernels/bu because the dataset is very unbalanced for locations between hybrids. As such, caution should be used with these results.
Figure 1. Representative kernels from the tip, middle, and butt of an ear from hybrid families with above-average (P1197) and below-average (P1082) kernel weight in 2019. Photo courtesy of Bill Long.
Table 1. Kernel weight as a percentage and standardized kernels/bu by hybrid family.
1Calculated as hybrid kernels per bushel compared to the location average kernels per bushel, then averaged over all locations.
2Calculated as the kernel weight percentage applied to a “normal” value of 80,000 kernels per bushel, rounded to the nearest 500.
3Only hybrids with a minimum of 3 locations were included.