360 



General Botany 



Cereal lHvesti(idt.un., L .S.D.A. 



Fig. 225. A field of kafir corn in western Oklahoma ; a good dry-land crop. 



soils. On the plains uplands it may produce two or three crops 

 of hay in a season ; on the lowlands it may produce three or 

 four, and in exceptional seasons, toward the south, five. Alfalfa, 

 like all clovers, has bacterial nodules on its roots that accumulate 

 organic nitrogen compounds. Thus by growing alfalfa in fields 

 for several years, the fields not only yield a good return, but if 

 the final crop is plowed under before planting other crops, the 

 soil will be improved in its nitrogen and humus content. The 

 growing of alfalfa has spread from the plains country into all 

 the Western irrigated districts and to the prairie and deciduous 

 forest regions. The drought-resistant millet grasses are of sec- 

 ondary importance as hay and forage crops on the plains and 

 prairie border. 



The western evergreen forest region. The plant industries 

 associated with the western evergreen forest are, for the most 

 part, lumbering and the manufacture of lumber products. As 

 the timber of the Eastern states became scarcer and poorer in 

 quality, the exploitation of these great Western forests began; 

 and now products from them, such as rough lumber, shingles, 



