116 



MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



seeds in the litter provided a sufficient reserve for 

 a second wave of germination. Seed dormancies of 

 from 50 to 80 percent were regarded as a valuable 

 mechanism for survival of the species. 



In general, germination is reduced with in- 

 creasing age of seeds. Older seeds often produce 

 malformed seedlings, some without the appear- 

 ance of a root or radical. Removal of a portion 

 of the seed awn of T. asper^am, (Jf£) appeared to 

 increase germination of older seeds, however. 



Williams (59) evaluated the emergence force 

 exerted by small legumes. On the basis of dif- 

 ferences in the force exerted, he concluded that 

 the seedling size was not always a reliable index 

 as to the force that the seedling was capable of 

 exerting. In heavy soils, choosing the species with 

 the ability to emerge under difficult conditions 

 would be a wise management decision for seeding 

 depleted annual rangelands. Grass species differ 

 significantly in their ability to emerge from dif- 

 ferent planting depths. The data in table 2 show 

 that T. asperum has a limited ability to emerge 

 from soil depths greater than 2 inches. 



Emergence of seedlings is often taken as an 

 indication that establishment has fully occurred. 

 This may be a reasonable criteria for the germin- 

 ation laboratory or in a humid environment, but 

 under annual range conditions, establishment is 

 not secure at this point. The number of plants 

 early in the growing season has been reported 

 (11) to vary from 20 to nearly 100 per square 

 inch. Considerable reduction in this number takes 

 place as the season progresses. In a review of 

 seedling vigor. McKell (36) stated that establish- 

 ment may not be fully assured until a grand rate 

 of plant growth has been demonstrated (fig. 2). 



Fertilizer may be applied in the area imme- 



Table 2. — Seedling emergence from i-, #-, 3-, and 

 4-inch planting depths. Each figure is an aver- 

 age of 15 observations 



Species 



Number of seedlings emerging 

 from depth of 



1 in. 



2 in. 



3 in. 4 in. 



Trifolium Mrtum 160 



Bronius mollis __' 259 



Taeniatherum asperum- 287 



91 



22 



1 



42 



1 







32 











u 

 Q 



c J- Period of Seedling Establishment 



El £ 



Time 



Figure 2. — Period of seedling establishment in relation 

 to succeeding stages of plant growth. (After McKell. 

 37.) 



diatel}- adjacent to grass seedlings (53). However, 

 Lolium multiforum seedlings supplied with ex- 

 tra nitrogen (1) failed to grow roots and tops 

 as fast as seedlings receiving no additional nitro- 

 gen. The ability to utilize nitrogen efficiently 

 must develop later, because older Lolium seed- 

 lings are known to be highly efficient users of fer- 

 tilizer nitrogen. 



Artificial Seeding 



The management of annual rangelands often 

 requires that improved species be introduced to 

 the plant community. The choice of adapted an- 

 nual grasses and legumes is extremely important 

 and has received considerable study ove'r the past 

 several years. Good management usually includes 

 drill seeding, fertilization, reduction of competi- 

 tion by grazing management, proper depth of 

 planting, and follow-up grazing management to 

 assure favorable conditions for seedling establish- 

 ment. 



In Bromus tectorum areas, concern has been ex- 

 pressed that sites formerly dominated by peren- 

 nial range grasses are almost impossible to re- 

 claim to perennial grasses because of the intense 

 competition offered by B. tectorum. Otherwise, 

 grazing management of the existing stand of 

 annual grasses appears to be the only solution 

 available at the present time. Recent work by 

 USDA's Agricultural Research Service range- 

 land scientists in Nevada and "Washington appear 

 to provide some answers for establishing peren- 

 nial grasses in the areas dominated by Bromus 



