EXPERIMENT STATION BULLETINS. 217 



OBSERVATIONS ON THE INFLUENCE OF NODULES ON THE 



ROOTS UPON THE COMPOSITION OF SOY 



BEANS AND COWPEAS. 



BY C. D. SMITH AND F. W. EOBISON. 



Bulletin No. 224. 



INTRODUCTION. 



The appearance of the very timely article on "Bacteria and the Nitrogen Prob- 

 lem" in the year book of the Department of Agriculture for 1902, page 333, 

 and of Bulletin No. 71 of the Bureau of Plant Industry, entitled "Soil Inocula- 

 tion for Legumes," has placed in the hands of the farmer somewhat full infor- 

 mation as to the present knowledge of the significance of nodules on the roots 

 of legumes. It is not the purpose of this bulletin to discuss the micro-organisms 

 involved in the production of these nodules nor to treat of inoculation of seed 

 and soil. That phase of the subject is left to another department of the station. 

 This bulletin is designed to put on record the results of certain investigations 

 made on the station plots, as to the influence of nodules upon the appearance 

 of the growing crops and upon the quantity and quality of the harvest. The 

 bulletin reports progress and not conclusions. 



I. THE INFLUENCE OF THE NODtlLES ON THE ROOTS UPON THE APPEARANCE OF THE 



PLANTS. 



The notes upon the station plots for three years record a great many occas- 

 ionS''upon which a very decided difference in color and thrift could be noted 

 be1*Ween plants in the same plot. Some of the plants would be dark in color 

 an^i'^'rather more thrifty in general appearance than others. In the case of soy 

 bea "^ where limited areas were thus noted, examinations were made of the 

 root^ ' In no case could the difference in color be ascribed to the presence of 

 nod"iil\i3. On a certain series of plots, marked G on the station map, a very con- 

 spicuous instance of this kind occurred. A certain area with well defined mar- 

 gins was conspicuous for its dark green color. About it the plants were of a 

 light color. An examination of more than a dozen plants in the dark colored 

 area, failed to disclose the presence of nodules. 



A field of soy beans was growing in another part of the station grounds 

 when a similar small area of dark colored leaves was noted. Here, as in the 

 other case, there was no relation between the color and the presence of the 

 nodules. In this case the plants were inoculated but the number of nodules 

 was no greater per plant where the color was dark than where the color was 

 light nor were the nodules larger. 



On several occasions equal areas were sown , to soy beans and cow peas, 

 one area inoculated and with nodules on the roots, the other area not inocu- 

 lated. As far as quantity of crop is concerned the results have not shown 

 a large and notable increase due to inoculation. 



II. THE INFLUENCE OF THE PKESENCE OF NODUT.ES ON THE COMPOSITION. 



On the 23d of September, 1903, there were growing on the station plots, 

 two areas of soy beans. On one of them the roots were practically free from 

 nodules, on the other the roots were well inoculated and nearly covered by 

 them. The variety of beans was the Medium Green, a late sort ripening its 



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