Spatial variation of protein, oil, and starch in corn

Significant spatial yield variations are known to exist in cornfields with different soil types, topsoil depth, and other variables. Similarly, variations might also be found among the highly valued chemical components (oil, protein, and starch) in corn kernels due to local differences in soil type, fertility, acidity/pH, organic matter, etc. This study quantified the spatial variability of protein, oil, and starch content of corn from two conventional cornfields and two high-oil cornfields. Whole ears were harvested by hand from 20 to 40 randomly selected locations within each field. A differential global positioning system (DGPS) receiver recorded the location of each collection site. Samples were also collected from hauling vehicles with a segmented probe prior to transport from the field and from the grain stream as trucks were unloaded. A NIRSystems 6500 near-infrared reflectance instrument was used to measure the protein, oil, and starch concentration of each sample collected. Yield maps were plotted for each type of corn along with protein, oil, and starch variation. Results showed large variations between the conventional and high-oil cornfields. Slight variations were found between truck probe samples from the same field. Oil content was more variable than protein or starch. Probe samples appeared to provide the most representative results. Segregation of grain based on average values of components in hauling vehicles appeared to be feasible. The oil concentration between truck hoppers was significantly different and could be used for binning corn of different concentrations. However, segregation on the combine during harvest does not appear to be feasible due to the large variations that occurred within fields at the same location. For example, the oil concentration of individual ears varied between 1 and 7 percentage points at the same location within the field.