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Response of Cotton to Varying COz, Irrigation, and Nitrogen: Yield and Growth

B. A. Kimball, J. R. Mauney
Agronomy journal 1993 v.85 no.3 pp. 706-712
source-sink relationships, carbon dioxide, lint cotton, seeds, Gossypium hirsutum, dry environmental conditions, irrigated conditions, dry matter accumulation, water stress, harvest index, photosynthesis, root shoot ratio, nitrogen fertilizers, Arizona
The CO₂ concentration of the atmosphere is increasing and is expected to double sometime near the middle of the next century. To determine the effects of such a CO₂ increase on cotton (Gossypium hirsutum L.) growth and productivity, a series of experiments from 1983 through 1987 were conducted with open-top CO₂-enriched field chambers at ample as well as limiting levels of water and N at Phoenix, AZ. Comparisons with open-field plots showed that there was a significant chamber effect, amounting to a 30% average increase in growth inside, but under dry conditions in 1985, the situation was reversed. No significant effects of CO₂ on harvest index, root-shoot ratio, or lint percentage were found, so the primary effect of elevated CO₂ was to produce plants that were larger. Comparing the results of 500 and 650 µmol mol−¹ CO₂ treatments, the increments of growth from ambient (about 350 µmol mol −¹) to 500 µmol mol−¹ were not significantly different from increments from 500 to 650 µmol mol−¹. No statistically significant interactions were detected between CO₂ level and either irrigation or nitrogen level, even when these variables were sufficiently low enough to limit growth. However, under well-maintained water stress conditions, the growth response to CO₂ tended to he somewhat larger than under normal irrigation levels. Averaging over all the data available from these experiments, seed cotton yield (lint plus seed) and above-ground biomass were increased by 60 and 63%, respectively, by CO₂ enrichmento 650 µmol mo1−¹. This research was partly supported by the U.S. Dept. of Energy, Carbon Dioxide Research Division, Interagency Agreement no. DE-A101-81ER-60001.