PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



41 



summer, while at cooler soil temperatures initia- 

 tion continued throughout each growing month. 

 New tillers per unit area were determined at each 

 harvest, and the accumulation of these are shown 

 in figure 5. The first count was made May 11, fol- 

 lowing the second forage harvest. Until this 

 date air-temperatures were relatively cool, and at 

 10° C. soil temperature tiller initiation was much 

 slower than at higher soil temperatures. In early 

 summer, as air temperatures increased, tiller ini- 

 tiation was most rapid at 10°. Throughout much 

 of the summer, there was little difference between 

 10° and 21°, but because of the large number in 

 spring, accumulation of new tillers was largest 

 at 21°. Where high soil temperatures were 

 avoided, large numbers of tillers were initiated 



O OOOeOOOO OOOO O OOPPPO O P OtMi 



S46000S00S005000S 



X WPCCOOOOOOOOO t 



tOOO Q OOQQOOOOQ OV Oet 



40 



8C 



120 16 200 



N / 005 SQ METER 



240 



Figure 5. — Accumulation of new tillers on Climax tim- 

 othy during the summer as influenced by soil tempera- 

 ture. 



Table 3. — Total live tiller numbers for three forage grasses grown at 

 four soil temperatures, 1966 



Soil 









Tillers per 0.05 m. s * 





temperature 



Species 



May 4 



Aug. 16 



Sept. 23 



Ambient 



Potomac 



337 



ab 



142 be 



129 b 





S-37 



332 



ab 



118 be 



128 be 





Climax 



302 



abc 



125 be 



102 bed 





Av. 



324 



AB 



128 B 



120 B 



32° C. 



Potomac 



171 



f 



99 c 



89 d 





S-37 



214 



<!<■ 



132 be 



87 d 





Climax 



196 



ef 



41 d 



76 d 





Av. 



194 



C 



91 C 



84 C 



21° C. 



Potomac 



289 



abc 



147 b 



120 be 





S-37 



252 



cd 



152 ab 



125 be 





Climax 



279 



bed 



126 be 



101 cd 





Av. 



273 



15 



142 AB 



115 B 



10° C. 



Potomac 



299 



abc 



165 ab 



182 a 





S-37 



352 



a 



198 a 



180 a 





Climax 



355 



a 



148 b 



182 a 





Av. 



335 A 



170 A 



181 A 



Average : 



Potomac 



274 



X 



138 X 



130 X 





S-37 



287 



X 



150 X 



130 X 





Climax 



284 X 



110 T 



115 Y 



CV, percent 





12.2 





18.0 



10.8 



1 Values within each column with the same letter are from the same statistical 

 population at the 5-percent level of significance. Capital letters are used for main 

 effects. 



