TITLE:
Corn Growth Response to Elevated CO2 Varies with the Amount of Nitrogen Applied
AUTHORS:
James A. Bunce
KEYWORDS:
Corn; Yield; Nitrogen; Elevated CO2; Photosynthesis; Stomatal Conductance; Leaf Area Index
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.3,
January
26,
2014
ABSTRACT:
Corn, with C4 photosynthetic
metabolism, often has no photosynthetic or yield response to elevated carbon
dioxide concentrations. In C3 species, the yield stimulation at elevated carbon dioxide concentrations often
decreases with nitrogen limitation. I tested whether such a nitrogen
interaction occurred in corn, by growing sweet corn in field plots in open top
chambers at ambient and elevated (ambient + 180 mmol·mol-1) carbon
dioxide concentrations for four
seasons, with six nitrogen application rates, ranging from half to twice the
locally recommended rate. At the recommended rate of nitrogen application, no
carbon dioxide effect on production occurred. However, both ear and leaf plus stem biomass were
lower for the elevated carbon dioxide treatment than for the ambient treatment at less than the recommended rate
of nitrogen application, and higher at the highest rates of nitrogen application. There were no significant
responses of mid-day leaf gas exchange rates to nitrogen application rate for either carbon dioxide treatment, and
elevated carbon dioxide did not significantly increase leaf carbon dioxide assimilation rates at any nitrogen
level. Leaf area index during vegetative growth increased more with nitrogen
application rate at elevated than at ambient carbon dioxide. It is concluded
that elevated carbon dioxide increased the responsiveness of corn growth to nitrogen
application by increasing the response of leaf area to nitrogen application
rate, and that elevated carbon dioxide increased the amount of nitrogen
required to achieve maximum yields.