|Pinter Jr, Paul|
|Brooks, T. - UNIV. OF ARIZONA|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 19, 1998
Publication Date: N/A
Technical Abstract: The seasonal dynamics of PAR absorptance and conversion efficiency by spring wheat (triticum aestivum L. cv. Yecora Rojo) were examined under field conditions at Maricopa, Arizona, using Free-Air Carbon Dioxide Enrichment (FACE). Plants were exposed to two levels of CO2 and two levels of nitrogen fertilization. A normalized difference vegetation index (NDVI) )was computed from frequent measurements of canopy reflectance factors. A linear PAR sensor was used to estimate the fraction of absorbed photosynthetically active radiation (fAPAR). Significant correlations were found between NDVI and fAPAR and the photosynthetic potential of the canopy as measured by chamber carbon assimilation rates. Elevated CO2 had no effect on crop maturity dates when nitrogen was adequate, a stimulatory effect on total biomass and yield, a minimal effect on the total APAR, and a 6 to 12% increase in light use efficiency. The reduced N treatment compressed the growing season by more than 10 days and reduced biomass and the total APAR by about 18%, but had minimal effect on LUE.