Greenhouse CO2 Enrichment Alternatives: Effects of Increasing Concentration or Duration of Enrichment on Cucumber Yields

Abstract

Extended duration (delayed venting) and greater intensity were investigated as alternatives for CO 2 enrichment of fall and spring greenhouse cucumber ( Cucumis sativus L.) crops in North Carolina. The use of rockstorages allowed greenhouses to be enriched an average of 83% longer than was possible in conventionally ventilated greenhouses. Differences in daily enrichment times between rockstorage and conventionally ventilated houses were greatest during periods of high temperatures and high solar radiation levels in the early fall and late spring. In the rockstorage houses, enrichment increased fruit weights from 31–57%. Plants enriched to 600 μl·liter −1 yield as well or better than those enriched to 1000 or 1200 μ·liter −1 CO 2 . In the conventional houses, enrichment to 1000, 3000, and 5000 μl·liter −1 raised yields 18.5–34.5% in Fall 1983, Spring 1984, and Fall 1984. Cucumbers enriched to 1000 μl·liter −1 produced slightly less than the control plants in Spring 1983, however. In the conventionally vented houses, spring crops yielded best at the highest CO 2 enrichment level, whereas for the fall crops the reverse was true.