22 THE FORAGE AND FIBER CROPS IN AMERICA 



such a plant reduces the yield by occupying land which could 

 have been more profitably occupied by a plant adapted to the 

 existing conditions. The plant is out of place; it becomes 

 a weed. 



Roots never fully occupy the soil. Those of different plants 

 occupy different portions of it. The roots of timothy grow 

 near the surface; clover roots grow deeper. Thus to a certain 

 extent they do not interfere with each other. When red clover 

 is sown with timothy the former usually dies after the second 

 crop, leaving the decaying roots and stems to furnish their 

 acquired fertility to the timothy and to succeeding crops. The 

 holes left by the decaying roots may perhaps in some cases 

 improve the mechanical condition of the soil. In many fields 

 some portions of the land are best adapted to timothy and other 

 portions best adapted to red clover. Under these conditions 

 a combination may yield the maximum crop. 



In some localities timothy does not reach its best develop- 

 ment until it has been sown two or three years. In the mean- 

 time the clover may occupy a portion of the ground with no 

 serious ultimate disadvantage, apparently, to the timothy. The 

 seeding with a miscellaneous mixture of grass seeds of varieties 

 of little or no value when sown alone has neither practical nor 

 experimental evidence in this country to commend it. Under 

 uniform conditions of soil, the maximum yields of hay are 

 obtained when but a single species exists. For pasturage, 

 several varieties may be desirable in order to furnish a suc- 

 cession of herbage throughout the season. The chief difficulty 

 in America is to find varieties adapted to our soil and climate 

 which will do this. (74) 



20. Calculating Mixtures. The amount of seed required per 

 acre may be stated in the number of pounds of viable pure 

 seeds or as the number of pounds of commercial seed of a 

 stated percentage of purity and standard of germination. In 

 this volume the latter mode of statement is employed. 



