96 



T. Lyttleton Lyon and James A. Bizzell 



An examination of this table shows that, except in the case of maize, the 

 nitrates are lower in the soil on which plants grew during the previous year 

 than in the soil kept unplanted during that time. It will be noticed also 

 that the nitrates on the unplanted soil are in the same order as they were 

 when the plats were planted. Thus, nitrates are highest in the soil pre- 

 viously planted to maize, next in that planted to potatoes, and lowest in 

 that planted to oats. This is brought out also in diagrams XXVI and 

 XXVIL 



In Table 37 is given a statement of the nitrates in the planted sections 

 of the plats in terms of the nitrates in the unplanted sections taken as 100. 

 In order to obtain these figures the nitrates in both planted ends of each of 

 the four plats planted to the same crop are averaged, and this average is 

 divided by the average for the nitrates on the unplanted sections of the 

 corresponding plats. This furnishes the most convenient means of com- 

 parison, as it removes more effectively than any other method the local 

 variations in the nitrate content of the soil. 



TABLE 37. 



Ratio of Nitrates in Soil of Plats Previously Planted to Nitrates in 

 Unplanted Soil 





Crop 



Surface eight inches 



Second eight inches 



Plat 



May 1 



June 5 



June 28 



May 1 



June 5 



June 28 



3612, 3613, 3622, 3623 

 3614, 3615, 3624, 3625 

 3616, 3617, 3626, 3627 



Maize 



Potatoes.. 

 Oats 



106 



72 

 72 



115 

 62 

 60 



100 

 83 

 65 



102 

 60 

 52 



102 

 60 

 94 



113 



83 

 69 



There is a distinct and characteristic difference in the nitrate content 

 of the soil previously bearing these different plants. While the experiment 

 covers only one season, the differences would seem to be too large and too 

 well-defined to be accidental. 



On July 1 the plats used in this experiment were drilled to millet. The 

 entire plats were planted, including the middle section of each j^lat which 

 during the preceding year had remained unplanted. The object in planting 

 millet was to ascertain how the growth of a crop on these plats would 

 correspond with the nitrate content, j 



