| Popis: |
Natural rubber is a critical agricultural material, and guayule (Parthenium argentatum Gray) is the most promising domestic, agricultural source. A study on guayule was initiated to provide information on the water requirements and plant water stress behavior for this new perennial crop. Measured evapotranspiration averaged 3000, 2410, 2040, 1720, 1470 and 1520 mm, from May 1981 to December 1982, in decreasing order of water applications on the six irrigation treatments from the wettest to the driest. These evapotranspiration values indicated that the water use by guayule can be higher than many former estimates for an arid-type crop. Plant canopy temperatures also showed a progressive increase in plant water stress as irrigation water amounts decreased. The two-fold decrease in evapotranspiration from the wet to dry treatments corresponded to a four-fold increase in plant water stress indices based on remote infrared thermometer measurements. Both the concepts of stress degree days and crop water stress index, evaluated over the entire growing cycle, correlated well with the measured evapotranspiration. Even though the guayule plant can withstand long periods of drought, moisture stress will occur within a relatively short period of time after an irrigation for the guayule crop. |
