Survey of mean particle length in whole-plant corn silage

Theoretical length of cut (TLOC) settings on forage harvesters vary as dairy farmers attempt to increase the mean particle length (MPL) of whole-plant corn silage (WPCS). Our objective was to evaluate the MPL of WPCS using 2 methods of determination in whole-plant and stover-fraction samples. Eighty WPCS survey samples were collected and represented varied TLOC settings and processor types and settings. Particle size distributions for determining MPL were measured using either the Penn State Particle Size Separator (PSPS) or the Wisconsin Oscillating Particle Separator (WIOS). The MPL of WPCS samples determined by PSPS and WIOS, respectively, were 12.0 versus 11.8 mm and for the stover-fraction samples were 11.8 versus 8.1 mm. The TLOC, indicated verbally by surveyed dairy farmers or their custom operator, was unrelated to MPL regardless of particle-separation method (P > 0.10) for both whole-plant and stover-fraction samples. However, MPL measured by PSPS and WIOS were positively related in both as-fed whole-plant (R2 = 0.62, P = 0.001) and dried stover-fraction samples (R2 = 0.60, P = 0.001). The elimination of kernels through hydrodynamic separation did not improve the relationship between verbal TLOC and MPL. A relationship between MPL of as-fed whole-sample and MPL of the stover fraction was observed (PSPS, P = 0.001; WIOS, P = 0.001) but with poor R2 values (PSPS, 0.25; WIOS, 0.18). The strong relationship between the 2 methods used to determine MPL in WPCS suggests that MPL may be measured adequately on farm by consultants using the PSPS.