PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



37 



Figure 2. — Field layout showing movable shades and irrigators in operation. Thermocouple at 30 cm. is shaded for 

 obtaining air temperature. Thermocouple at 7.6 cm. is within the grass canopy. 



during a growing season are presented (fig. 3). 

 One week after equipment was activated, soil 

 temperature differences were well defined even 

 though target temperatures were not exact. On 

 April 19 at 0600, there was no difference be- 

 tween the ambient and 10° temperature profiles 

 (fig. 4). By afternoon, they began to separate, 

 and the weekl}' average showed a difference of 

 3° C at 8 cm. Profiles for the 21° and 32° tem- 

 peratures were well defined. In mid-July, when 

 air temperatures often reached the high 30's, 

 temperature profiles were skewed to the right 

 at the soil surface. Plots were irrigated differ- 

 entially in an attempt to maintain uniform soil 

 moisture as measured by soil tensiometers placed 

 near the surface. This required more frequent 

 irrigation of warm temperature plots. 



This report deals with experiments conducted 

 in these plots from 1964 through 1970. A small 



part of the data will be presented and discussed 

 in terms of similarities and differences with 

 greenhouse and growth chamber studies. 



The first major consideration was to determine 

 the degree of environmental control possible and 

 the magnitude of plant responses. With this in 

 mind the facility was uniformly seeded to 'Po- 

 tamac' orchardgrass (Dactylis glomerata L.). The 

 design was a randomized split plot with three 

 replications. Whole plots were four soil tempera- 

 tures, sub-plots were full sunlight vs. shade (65 

 percent in 1964 and 75 percent in 1965), sub-sub- 

 plots were 28 vs. 84 kg. N/ha, and sub-sub-sub- 

 plots were stubble heights of 3.5 vs. 8.5 cm. Dry 

 matter, tiller number, persistence, and chemical 

 composition data were obtained. 



Because of marked shifts in maturity and per- 

 sistence, 'S-37' orchardgrass (late maturing) and 

 'Climax' timothy (Phleum pratense L.) (similar 



