Wednesday, November 15, 2006

Variability of Chlorophyll Meter Readings of Individual Maize Plants.

Paul Hodgen1, Fernando Solari1, J. S. Schepers2, R. Ferguson1, and John Shanahan2. (1) Univ of Nebraska, 1132 N 45th St, Lincoln, NE 68503, (2) USDA-ARS, 120 Keim Hall, East Campus, Lincoln, NE 68583

There has been increasing work done on measuring and fertilizing individual corn plants.  There has been extensive research using a Minolta 502 SPAD meter to estimate chlorophyll content in various crops and to use this information to make more informed nitrogen (N) fertilizer decisions.  The purpose of this study was to determine the variability in yields and N status of individual plants in the high yielding irrigated area of the Central Platte Valley in Nebraska.  SPAD meter readings were taken on strips of rows of approximately 30 meters in length, for two years on an experiment station and surrounding farmer fields.  There were 5 SPAD meter readings taken per plant at V16 and R1 on either the upper most expanded leaf or on the ear leaf depending on the growth stage at the time of data collection.  Each plant was then hand harvested at physical maturity and the grain shelled and recorded.  Data indicate that a SPAD meter can be used to detect differences in individual plant yields.  The variability in observed grain yields varied from 0 to nearly 250 g plant-1, while the SPAD meter readings varied from approximately 30 to 65 units.  SPAD meter readings explained nearly 55 % of the variability of over 1500 individual plant yields.  These data may be helpful in the use of a 502 SPAD meter to make fertilizer recommendations in corn cropping systems.