Oct. 1, 1921 



Effect of Soil Temperature on Development of Nodules 29 



the colorometric method of a composite sample of the soil at the begin- 

 ning of the experiment and of a sample from two cans of soil at each 

 temperature when the plants were harvested. In addition, in order to 

 get some clue to intervening changes, an unplanted can of soil was kept 

 at each temperature from which a sample was taken at about the middle 

 of the period. The results obtained are shown in Table IV. The effect of 

 soil temperature does not appear to have been as definite and consistent 

 upon the concentration of nitrate nitrogen as was anticipated. Until 

 further data are available, it seems unwise to attempt to interpret the 

 results. However, the very absence of large and consistent modifica- 

 tion enables us to believe that this factor was not important in its effect 

 upon nodule development. The only point at which nitrate accumula- 

 tion became very large occurs in the second series where the unplanted 

 soil shows at the end of 26 days a very high nitrate content at 21° 

 and 24° C. If it is assumed that a similar concentration took place in 

 the planted pot at an early stage in the development of the plants be- 

 fore they were large enough to reduce it by absorption, it would be an- 

 ticipated that a reduction in nodule production would be found here. 

 In fact, however, this point of high nitrate formation is the point of 

 highest nodule production, just as it is in the first series where no evi- 

 dence of high nitrate content at any time was obtained. 



Table IV. — Nitrate nitrogen in the soil in which the soybeans grew and also in 



unplanted soil 



MOISTURK CONTENT OF THE SOU. 



In view of the effect which high moisture content of the soil is reported 

 by Wilson ^ and others to have in increasing nodule production, the 

 moisture content of the soil in the later series was kept uniform at all 



'Wilson, ]. K. physiologicai, studies of bacillus radiocola of soy bean(soja max piper) and 

 OP FACTORS INFLUENCING NODULE PRODUCTION. N. Y. Cornell Agr. Exp. Sta. Bui. 386, p. 363-413, fig. 

 80-94. 1917- 



