Soil Nitrate Studies 



275 



ahead of the unlimed plot most of the time. Both plots showed a low 

 nitrate content in May and early June. Both plots were plowed for 

 wheat about August 20. The increase in conservation of moisture and 

 aeration resulting from the plowing probably caused the great increase 

 in nitrification in September. In both cases the incubated samples with 

 ammonium sulphate showed a substantial increase in nitrification over 

 the samples without it. This condition was probably caused by a de- 

 ficiency of quickly available organic nitrogen, resulting from the con- 

 tinuous cropping. By comparing the two plots, it would seem that 

 liming tends to increase nitrification. 



TABLE VI.— SERIES 3 WEST 



Date 



Plot 15 Continuous Corn (Rye) 



Moisture 

 Per Cent 



Nitrates — Parts per Million 



Incubated 



II 



April 21.... 



May 6. . . . 



May 20... 



June 3. . . . 



June 17. . . . 



July 1 . . . . 



July 15.... 



July 29.... 



Aug. 12 



Aug. 26.... 



Sept. 9.... 



Sept. 23.... 



Oct. 14. . . . 



Oct. 30... 



Average 



26.55 

 23.53 

 23.90 

 20.91 

 19.46 

 19.19 

 22.03 

 19.49 

 17.61 

 21.06 

 17.96 

 16.09 

 24.76 

 23.28 



21.12 



3.92 



9.38 



11.56 



12.13 



11.20 



24.49 



25.76 



17.64 



15.23 



9.61 



7.48 



11.52 



9.24 



3.46 



12.33 



8.96 

 11.80 

 19.86 

 22.58 

 21.70 

 27.80 

 23.22 

 21.80 

 21.96 

 19.67 

 15.26 

 16.94 

 16.38 

 12.60 



20.61 



15.60 

 28.65 

 24.93 



26.85 

 36.18 

 43.92 

 44.29 

 46.77 

 43.44 

 38.76 

 32.49 

 31.55 

 26.87 

 25.82 



33 22 



Discussion of Series 3 West (Continuous Corn). (Table VI.) 



This plot, like plots 13 and 14, has been continuously cropped. Rye 

 has been sown in the corn in the autumn and plowed under in the 

 spring. The moisture content was about optimum during May as a 

 result of the heavy growth of rye that had been turned under which 

 permitted the surface water to soak in more quickly, while the soil 

 from the other corn plots was above optimum in moisture. The above 

 explanation probably accounts for the fresh nitrate content being higher 

 at that time than in the case of the other corn plots. The highest point 



