Reliability of Chlorophyll Meter Measurements Prior to Corn Silking as Affected by the Leaf Change Problem

Abstract

The normal practice of using chlorophyll meters involves measuring the youngest fully developed leaf of a corn plant (Zea mays L.) before silk emergence and then switching to the ear leaf. A discontinuity exists of chlorophyll meter measurements associated with leaf change prior to the silking stage. The lag of silk emergence within a cornfield prior to silk emergence makes it practically impossible to take chlorophyll measurements on leaves at the same growth stage. Therefore, the change in leaves being measured introduces errors when chlorophyll meters are used prior to silk emergence to diagnose nitrogen (N) deficiencies. We report results from three field studies to assess the difference in chlorophyll measurements between the uppermost fully developed leaf and the ear leaf near the time of silk emergence and identify possible problems associated with the difference when chlorophyll meters are used to estimate the need for in‐season fertilization in cornfields.

Keywords:

• Chlorophyll meters
• growth stage
• leaf change
• nitrogen
• silk emergence
• SPAD

ACKNOWLEDGMENTS

Special thanks to Yiran Zhang for proofreading this manuscript and for her valuable comments.