Abstract: A system and adjustable apparatus for applying CO2 gas to improve Cannabis production. The system includes upstream and downstream stages or subsystems. The upstream subsystem receives and stores gas, particularly CO2 gas. It monitors the environment of the downstream subsystem, determines when and how to apply gas to plants growing in the downstream system, acquires gas stored in the upstream subsystem, and distributes it to the downstream system. It also has various monitoring, command and control, management, and reporting features. The downstream subsystem includes one or more plant growth areas or plots, gas distribution means, such as gas conduits, tubes or lines from the midstream subsystem, and the high efficiency, adjustable gas applicator, and various sensing and monitoring devices communicatively connected to the upstream subsystem. Also disclosed are systems, apparatus and methods for pest control, humidity control, and odor control.