The Carbon Dioxide Content of Field Air

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Abstract
The CO2 content of field air was measured at 1 m in a field of maize ana on an adjoining tower to a height of 152 m. CO2 content of the air increased in the field during a still night to as much as 0.04%, but was about 0.03% on a windy night. It dropped quickly after sunrise to 15 or 20% below the "normal" value of 0.03%. CO2 concentrations at 152 m were close to 0.03% at night, and dropped 10 to 12% during the day. Values at 30 m were close to those at 152 m and 10 m was intermediate. A maximum night time accumulation of 11 lbs.CO2 an acre was observed while daytime deficits, because of much greater height, were 100 lbs. an acre and more. CO2 apparently moves from the air toward the vegetation level during the day, and is probably limiting for photosynthesis at the concentrations observed. After killing frosts CO2 fluctuated irregularly; values at 1 and 152 m were nearly equal and slightly higher than the midsummer readings.