Measurements of Photosynthesis and Evapotranspiration in Turfgrass Under Drought Stress with a Custom Surface Chamber.

Field measurements of photosynthesis in turfgrass are often conducted with surface chambers that cover a small area of the canopy. Measurements with typical portable photosynthesis systems may take up to four minutes, during which time the conditions that affect photosynthesis (e.g., air temperature) may change significantly inside the chamber. We fabricated a large turfgrass chamber that measured photosynthesis in about 30 to 40 sec. Furthermore, we added an infrared thermometer (IRT) inside the chamber to measure canopy surface temperature, which allowed for estimates of surface conductance to water vapor flux.  Measurements were made during drought stress on 4 cultivars of Kentucky Bluegrass (Poa pratensis L.) and a Texas bluegrass hybrid in the summer of 2009.  Ancillary measurements of soil water content at 5 and 20 cm were also collected.