Figure 3. Daily trends of leaf water potentials of Kentucky bluegrass and Western wheatgrass on different grazing treatments and different days at the CGREC field site. Also shown are hourly averages of solar radiation, air relative humidity and air temperature, which are from the CGREC weather station. Leaf water potentials are shown as means standard errors. Differences between two grass species at particular times of day are significant (by t-test at alpha=0.05) unless labeled otherwise by an "ns". Under severe moisture stress, the number of Kentucky bluegrass samples (out of the total number of samples measured at particular times) whose water potentials were not accurately measured, due to shortage of nitrogen gas or the limit of the measurement range of the equipment, is indicated as a fraction.