CARBON DIOXIDE UPTAKE EFFICIENCY IN RELATION TO CROP-INTERCEPTED SOLAR RADIATION

In order to apply supplementary CO₂ economically, we must make certain that during each hour of CO₂ enrichment the Carbon Dioxide Uptake Efficiency (CDUE) (i.e., the ratio of CO₂ assimilated by the crop to CO₂ applied to the greenhouse air) remains above an economic break-even point.

A comparison of CDUE in four modes of CO₂ enrichment is made: 1) constant CO₂ supply rate, 2) constant CO₂ concentration, 3) pulsed CO₂ enrichment (i.e., repeated cycles of a period with elevated CO₂ concentrations followed by a ventilation period without CO₂ enrichment) and 4) constant CDUE. The influence of crop-intercepted solar radiation on CDUE at different air exchange rates and at different elevated CO₂ concentrations is discussed.

Two methods for measuring CDUE are given.
Over short periods of time (minutes and hours) CDUE can be measured by gas exchange measurements of CO₂ and of an inert tracer gas (for instance N₂O). Over longer periods (weeks and months) CDUE can be measured by isotope analysis of ^13C and ^14C in atmospheric CO₂, in fossil CO₂ supplemented to the greenhouse, and in plants with and without CO₂ enrichment.

Symposium on CO2 Enrichment

H.Z. Enoch

https://doi.org/10.17660/ActaHortic.1984.162.13