Relations of Higher Plants to the Formation of Nitrates 101 



mary and the secondary crops were all planted at the same time, in spite 

 of which the secondary crops did not suffer greatly from the competition. 

 In Table 41 are given the yields of the primary crops in the mixtures as 

 compared with the yields of the same crops in the single cultures when the 

 latter are taken as 100. In this comparison the same number of plants is 

 taken in both the single and the mixed cultures. In some cases the 

 secondary crop grew fairly well and in other cases the growth was slight. 

 The relative yields of the primary crop and the secondary crop in the same 

 squares are stated in the table. The yields are based on weights of the 

 water-free material. 



TABLE 41. 



Relative Yields of Primary Crops Grown Alone and of Primary Crops 

 IN Mixtures on Greenhouse Soil 



Primary crop 



Secondary crop 



Yield of 



primary 



crop grown 



in mixture 



when 



primary 



crop alone 



la taken as 



100 



Yield of 

 secondary 

 crop when 

 primary 

 crop in 

 mixture is 

 taken as 100 



Period of 



growth of 



primary 



crop 



(days) 



Period 



between 



planting 



primary and 



secondary 



crops 



(days) 



Dandelion. . . 

 Timothy . . . . 



Wheat 



Oats 



Oats 



Oats 



Oats 



Wheat 



MUlet 



MiUet 



Spring wheat 

 Spring oats . . 



Peas 



Timothy . . . . 

 Wheat 



Timothy. . . 

 Mustard. . . 

 Mustard. . . 

 Mustard. . . 

 Mustard. . . 



Maize 



Maize 



Maize 



Maize 



Maize 



Winter oats 

 Winter oats 

 Lettuce . . . . 



Redtop 



Rye 



102 



127 

 93 



132 

 98 



133 



107 

 97 

 98 

 88 

 69 

 92 



100 

 99 



112 



20 



13 







2 



2 



40 



15 



1 



166 



128 



146 



142 



87 



107 



93 



93 



63 



84 



151 



151 



67 



130 



84 



91 



67 

 72 

 72 

 46 

 72 

 58 

 61 

 44 

 65 

 71 

 70 

 37 

 29 

 49 



It is seen from this table that in some instances the yield of the primary 

 crop in the mixture was as large as, or larger than, when grown alone. As 

 this occurs in nearly half of the cases, it appears at first glance that the 

 larger yields are accidental and not due to any influence exerted by the 

 secondary crop. Taken by themselves these results could not be said to 

 indicate anything, although the fact that nearly half of the tests gave 



