In 1983 and 1984 cotton plants were exposed to 350, 500 and 650 ppm CO₂ in field enclosures. Plant growth parameters and water use were monitored. In 1984 one group of treatments was irrigated with two-thirds the volume of water deemed adequate for maximum production.

In 1983 the experiment was planted late, on June 15 and CO₂ enrichment resulted in a yield increase of about 70%. In 1984 the increase due to enrichment was 95%. The CO₂ enrichment at 500 ppm was intermediate it, yield response to the 650 ppm.

All growth and boll retention observations were increased by the CO₂ enrichment by about the same ratio as that of yield. The larger leaf areas of the CO₂ enriched treatments caused water use to be the same in all treatments. Water use efficiency was increased by enrichment due to the greater yield. Mid-season rains added sufficient water to the water stressed treatments so that no effect of water stress was observed on final yield.