OBJECTIVES AND LIMITATIONS OF ENVIRONMENTAL CONTROL
Because of interactions between the crop and the environment, the relation between the measurement made by control engineers and the environment at the plant surface is sometimes very complex. Some environmental factors should probably be controlled in relation to the intensity of the solar radiation, but in a glasshouse this varies greatly in time and space, and it is not possible to make allowance for the fine structure of this variation.
Engineers use physical criteria to assess a control system but a horticulturist must decide whether the cost of improving control has been balanced by increased value of the crop. Present control systems cannot match skilled growers who use the environment as a tool in controlling the condition of the plants hour by hour throughout their lives.