Corn Response to Differential Removal of Leaves from the Upper and Lower Canopy

Abstract

Although considerable information is available on the impact of whole-plant defoliation on the performance of corn, little is known concerning the response of corn to differential defoliation of the upper and lower canopy. The objective of this study was to determine effects of defoliation above and below the ear during grain fill on the agronomic performance of two hybrids differing in maturity. Defoliation treatments involved 50 and 100% removal of leaf tissue above and including the ear leaf, and 50 and 100% removal of leaf tissue below the ear leaf. Defoliation treatments were imposed at four grain fill stages: silking (R1), blister (R2), milk (R3), and dough (R4). Yield losses and stalk rot were greatest at R1 with 100% leaf removal above and including the ear leaf. Grain moisture at harvest was lowest in corn with complete upper canopy defoliation. Fifty and 100% defoliation of the upper canopy at silking resulted in yields 76 and 48% of the untreated check (UTC), whereas 50% and 100% defoliation of the lower canopy resulted in yields 93% and 81% of the UTC. By R4, yield losses from lower canopy defoliation were negligible (less than 5% of the UTC), whereas yield losses from upper canopy defoliation were 11% and 28% of the UTC for the 50% and 100% leaf removal treatments.