Net carbon dioxide exchange of wheat, sorghum, and soybean

Abstract

Canopy net carbon dioxide exchange (NCE) rates are needed to understand the effect of light on crop growth and development. NCE rates of sorghum, soybean, and wheat canopies were determined using field chambers and an infrared gas analyzer throughout a growing season. Whereas sorghum attained peak NCE rates early in season, soybean and wheat did not reach maximum rates until the late reproductive growth stage. Frequently during the season, NCE rates of sorghum were nearly four times those of soybeans and wheat. Solar radiation had a much greater affect on the NCE of sorghum than on that of soybeans. Apparent light saturation was observed in both soybeans and wheat. An expression for dry matter production of sorghum was derived using chamber data. The expression simulated the total dry matter production for sorghum in 1973, 1972, and 1970 within 20%.