104 



T. Lyttleton Lyon and James A. Bizzell 



of the primary plants when grown in combination than when grown alone. 

 The field soil used was Dunkirk clay loam. 



TABLE 43. Relative Yields of Primary Crops Grown Alone and of Primary Crops 

 Grown in Mixtures on Field Soil 



Primary crop 





Yield of 





primary 





crop grown 





in mixture 



Secondary crop 



when 





primary 





crop alone 





is taken as 





100 



Buckwheat 



166 



Buckwheat 



126 



Buckwheat 



132 



Buckwheat 



106 



Mustard 



115 



Mustard 



102 



Mustard 



116 



Mustard 



105 



Lettuce 



40 



Lettuce 



58 



Red clover 



104 



Red clover 



122 



Maize 



107 

 94 

 83 



Maize 



Maize 



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) 



Barley 

 Barley 

 Oats. . 

 Oats. . 

 Oats. . 

 Oats. . 

 Barley 

 Barley 

 Peas. . 

 Peas. . 

 Oats. . 

 Oats. . 

 Oats. . 

 Barley 

 Barley 



37 



79 



35 



55 



37 



99 



38 



39 



172 



169 



175 



143 



25 



50 



34 



67 

 70 

 70 

 73 

 70 

 73 

 67 

 70 

 35 

 38 

 40 

 43 

 68 

 70 

 70 



30 

 30 

 31 

 31 



27 



25 



24 



24 



*— 35 



—35 



—28 



—28 



38 



37 



37 



* The minus sign indicates that the secondary crop was planted before the primary crop. 



In the field soil a major proportion of the tests resulted in a larger yield 

 of the primary crop in the mixtures than when grown alone. As in the 

 previous tests, a particularly heavy yield of a secondary crop was accom- 

 panied by a relatively lighter yield of the corresponding primary crop. 

 This is very noticeable in the combinations of barley and buckwheat, 

 oats and buckwheat, and oats and mustard. It is not possible to trace 

 any relation between the influence of the secondary crop and the length 

 of the growing period or the length of time between planting, as the dupli- 

 cates do not vary much in these respects. 



Certain plants that were used as secondary crops were particularly 

 successful in promoting a good growth of the primary crops. These 

 were mustard, buckwheat, maize, and red clover. In the experiments 



