42 



MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



and a high percentage of these survived even in 

 midsummer with high air temperatures. 



Crown and root weights were taken on repre- 

 sentative plants at the end of each season, but 

 only 1966 crown and root data are presented 

 (table 4). Orchardgrass produced significantly 

 more crown and root growth than timothy. Av- 

 erage crown development significantly increased 

 with cooler soil temperatures, with little differ- 

 ence between ambient and 21°. Orchardgrass did 

 relatively better than timothy at higher soil tem- 

 peratures. 



Soil temperature markedly affected crown and 

 root development and plant survival of red clover 

 placed in a solid timothy stand (fig. 6). All MD 

 Syn-1 plants survived and produced significant 

 growth at all but 32°, where growth was as high 



CK. 



IOC 



21 C 



32 C 



Figure 6. — Crown and root production of Dollard (D) 

 and Maryland Syn-1 (M) red clover grown in a solid 

 timothy sod at four temperatures. (Note: No Dollard 

 plants survied at 32° C. ) 



Table 4. — Effect of soil temperature on crown and root growth of three 

 forage grasses grown at four soil temperatures, 1966 



Soil 







Dry matter per plant 



(100 g.) 1 



temperature 



Species 



Crown 



Root 



Total 



Ambient 



Potomac 



1.99 



b-e 



2.05 c 



4.04 bed 





S-37 



2.43 



abc 



1.95 c 



4.38 be 





Climax 



1.10 



cde 



1.08 cde 



2.18 e 





Av. 



1.84 



B 



1.70 B 



3.54 B 



32° C. 



Potomac 



.88 de 



.73 de 



1.61 e 





S-37 



.92 



de 



.77 de 



1.69 e 





Climax 



.68 



e 



.63 e 



1.31 e 





Av. 



.83 



P 



.71 C 



1.54 C 



21° C. 



Potomac 



1.58 



b-e 



2.22 be 



3.80 cd 





S-37 



1.89 



be 



1.84 cd 



3.73 cd 





Climax 



1.28 



cde 



1.25 cde 



2.53 de 





Av. 



1.58 



C 



1.77 B 



3.35 B 



10° C. 



Potomac 



2.89 



ab 



4.99 a 



7.88 a 





S-37 



3.54 



a 



5.00 a 



8.54 a 





Climax 



2.26 



a-d 



3.16 b 



5.42 b 





Av. 



2.89 



A 



4.38 A 



7.27 A 



Average : 



Potomac 



1.83 



X 



2.50 X 



4.33 X 





S-37 



2.19 



X 



2.39 X 



4.58 X 





Climax 



1.33 



Y 



1.53 Y 



2.86 Y 



CV, percent 





42.7 





28.5 



21.0 



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. 



