Impact of Defoliation on Corn Forage Quality

Hail damage can be a serious problem on corn (Zea mays L.) grown for silage. The value of corn grown for silage is a function of both the yield and quality of the forage produced. An improved understanding of the effects of defoliation on forage quality would improve the ability of agronomists, farmers, and crop insurance adjusters to assess the economic impact of hail damage to corn harvested for forage. The objective of this study was to evaluate the effects of defoliation on the forage quality corn grown for silage production. Experiments were conducted during 2000, 2001, and 2002 at Arlington and Marshfield, WI, and State College, PA. Corn quality measures responded similarly to defoliation treatments across most environments. Increasing defoliation either did not affect quality, especially at V7 and V10 stages, or lowered quality, especially at the R1 and R4 stages of development. The largest differences in neutral detergent fiber (NDF), acid detergent fiber (ADF), and in vitro true digestibility occurred at R1 and R4. Starch content was most affected when defoliation occurred at R1. The response of NDF digestibility was inconsistent across environments. These changes in forage quality resulted in decreases in Milk Mg-1 and Milk ha-1 with increasing defoliation in most environments. Predictive models for estimating forage quality and yield losses can be used to improve estimates of the impact of defoliation caused by hail on corn grown for silage.