Agricultural research uses controlled gas environments to study how crops respond to atmospheric composition, to measure gas exchange in leaves and soil, and to develop post-harvest storage protocols. This is distinct from commercial greenhouse CO2 enrichment operations, which use direct CO2 supply systems rather than research-grade gas mixers.
Photosynthesis and gas exchange measurement
CO2 response curves (A/Ci curves) are a standard measurement in plant physiology: a leaf is held in a cuvette, CO2 concentration is stepped from sub-ambient to elevated levels, and photosynthetic rate and stomatal conductance are recorded at each step. The gas mixer provides the CO2/air blends at each setpoint, with humidity controlled independently to avoid artefacts from stomatal response to vapour pressure deficit. Isotopic labelling experiments with 13CO2 use dynamic mixing to set the 13C/12C ratio precisely in the feed gas.
Elevated CO2 crop research
Understanding how crops will perform under future atmospheric conditions requires controlled-environment growth experiments at elevated CO2 concentrations, typically 600–1000 ppm versus current ambient levels near 420 ppm. A dynamic mixer holds CO2 at any target concentration throughout a growth experiment, enabling replicated comparisons between atmospheric treatments that cannot be achieved at low cost with field-scale open-top chambers or FACE installations.
Abiotic stress studies
Waterlogging causes soil oxygen depletion and elevated CO2 at root level. Controlled reduction of O2 in a root chamber, with independent humidity control, isolates the physiological response to hypoxia from soil chemistry effects. Similar approaches are used for drought (humidity ramps over a root zone), heat stress with combined humidity variation, and combined stresses that represent realistic field conditions.
Post-harvest physiology research
The correct storage atmosphere for extending shelf life of a specific fruit or vegetable variety is determined by research: lab-scale chambers expose produce to defined O2, CO2, and ethylene concentrations, with the atmosphere adjusted between or during experimental treatments by a calibrated gas mixer. Results inform commercial controlled atmosphere storage specifications.
Soil gas exchange and microbial studies
Carbon and nitrogen cycling in soil involves production and consumption of CO2, N2O, CH4, and O2 by microbial communities. Measuring these fluxes under controlled inlet gas compositions, and studying how soil microbiota respond to specific atmospheric conditions, requires a reproducible and adjustable gas supply to the soil sample or column.
