Average Tw ranged from 16.5 to 24.7 8C and differed by 4.6–7.4 8C between low and high Tw treatments, and maximum Tw averaged for the treatment period ranged from 19.5 to 29.7 8C and differed by 7.3–8.1 8C between low and high Tw treatments in each period tested. Yearly variation in Tw followed trends in Ta and Rd, such that Tw in 1998 was relatively