The CO2 flux concentration gradient and microclimate characteristics of a summ er corn community were measured with an infrared CO2 analysis system and a Bow en ratio device. The instantaneous CO2 flux density and the water use efficie ncy of the corn canopy were calculated. The result showed that the CO2 flux a nd CO2 concentration gradient as well as the water use efficiency of the summe r corn community had distinct daily and seasonal change patterns. The daily cha nge of the water use efficiency was described in a 'L'type curve with a peak value around 8 a.m. in the morning. Before grain filling, the water use effi ciency increased as the corn grew, while it decreased after grain filling becaus e of the decrease of photosynthetic ability of the corn community and the increa se of respiration consumption. The water use efficiency was affected by the fac tors such as global radiation and CO2 concentration and air saturation deficit etc. Therefore, in agricultural practice, the water use efficiency of the corn community could be raised by means of straw cover and sprinkling irrigation to reduce drive potential of transpiration.
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