26 



T. Lyttleton Lyon and James A. Bizzell 



it may be taken for granted that factors other than this are more impor- 

 tant in nitrate formation. These figures are shouii graphically in Dia- 

 gram T. 



Changes in soil moisture. — While the gradual changes in soil moisture 

 content that have been examined do not appear to have constituted an 

 important factor in promoting nitrate formation - — at least not sufficient 

 to prevail over other influencing conditions — the question arises whether 

 the more frequent, although less marked, changes in moisture content 

 due to the effect of transpiration from the plant in drjdng out the soil 

 between rains would not cause greater nitrification on the planted than 

 on the unplanted sections of the plats. 



Analyses made in the course of the experiments here described give 

 the daily moisture content of the planted sections on certain plats 

 throughout the growing season. There were also moisture determinations 

 made in each of the soil samples in which nitrates were determined, 

 and these show to what extent the cropped soils dried out as compared 

 with the uncropped . soils. These data are given in tables 5 to 7 : 



TABLE 5. 



Daily Determinations of Moisture in Soil under Timothy, 1907 

 (Percentage of Dry Soil) 



Date 



Plat 711 



Plat 720 



Plat 728 



Plat 729 



June 



6 



7 



23.3 

 30.7 

 25.0 

 21.2 

 20.9 

 19.3 

 19.0 

 18.9 

 23.0 

 14.9 

 30.3 

 37.2 

 35.1 

 21.0 

 18.7 

 18.6 

 . 22.4 

 22.8 

 20.6 

 19.4 



27.3 

 32.6 

 27.5 

 23.4 

 23.7 

 24.5 

 23.0 

 23.4 

 24.6 

 18.6 

 32.6 

 40.0 

 38.8 

 24.0 

 22.1 

 22.4 

 24.6 

 20.3 



""2L7 



25.0 

 29.9 

 24.5 

 20.7 



"20^6 

 18.9 

 17.6 

 20.6 

 16.6 

 31.0 

 37.1 

 36.8 

 22.2 

 19.3 

 17.3 

 21.9 

 18.6 

 19.6 

 17.7 



27.5 

 34.5 



8 



28. a 



11 



12 



13 



23.4 

 23.4 

 23.3 



14 



15 



17 



18 



19 



21.7 

 22.8 

 25.4 

 18.9 

 32.4 



20 



21 



22 



24 



25 



26 



27 



41.8 

 40.2 

 25.6 

 - 22.8 

 23.6 

 27.3 

 23.8 



28 



25.3 



29.... 



22.2 



