MEADOWS AND PASTURES 93 



So far as hay plants are concerned, experience and 

 experiments both show that as a rule larger yields are 

 secured from mixtures than from pure cultures. Ex- 

 ceptions are, however, found in such crops as alfalfa and 

 sometimes Italian rye-grass, mainly because no other 

 plants will coincide with either of these in producing 

 several cuttings. 



Among the reasons why mixtures yield better as a rule 

 than pure cultures are the following : 



1. The diverse root habits of the different crops make 

 their distribution through the soil more thorough. 



2. Their differing requirements do not make them 

 direct competitors, but enable them more thoroughly 

 to utilize the soluble substances of the soil. 



3. The average annual return can be made more nearly 

 even over a longer period by including both short-lived, 

 quick-growing plants, and long-lived plants. 



4. The loss by insects or disease is lessened, as most of 

 these attack but a single plant species. Thus, pure cul- 

 tures furnish far better opportunities for their increase 

 and spread than do mixed cultures. In mixtures, such 

 losses are often confined to but a single species in the mix- 

 ture ; and as this leaves more room for the others to de- 

 velop, there is at least a partial compensation for the 

 damage. Practically the same facts hold true if any of 

 the species in the mixture are destroyed or injured by 

 drought or other adverse weather conditions. 



5. The leaves and shoots of different grasses and legumes 

 vary greatly in habit and in light requirement. Some 

 low-growing species do well in the shade of taller species, 

 and thus the total quantity of herbage is increased. 

 Low-growing plants form the so-called " bottom grass " 

 in contrast to the " top grass " of tall species. A mixture 



