Soil Nitrate Studies 



273 



July 15. From then on until the last sample was taken it steadily went 

 down, differing in this respect from the previous wheat plots discussed. 

 The addition of ammonium sulphate to the incubated samples caused 

 a large increase, more at the beginning of the period than toward the 

 end. This instance again seems to show that it is in the beginning of 

 the season that crops need applications of quickly available nitrogenous 

 fertilizers. 



The nitrate content of the fresh samples of the corn plot was also 

 highest on July 15. The curve goes down with a few fluctuations until 

 October 30, being similar in this respect to the wheat plot in this series. 

 No explanation can be offered for this difference from the plots of the 

 other series. The incubated samples with ammonium sulphate showed a 

 much larger increase over those without ammonium sulphate than in 

 the case of the previous corn plots. This condition may have been due 

 to the fact that there is no clover and timothy crop in this rotation; 

 and hence there was not as much available nitrogen present (in previous 

 years the stand of clover was better than this past season). 



For some reason, not apparent, the fresh nitrates of the oat plot 

 were higher on April 21 than at any other time during the season, 

 and this in view of the fact that there had been a period of almost in- 

 cessant rain immediately preceding that time. During the rest of the 

 season the fresh nitrates were low, being lowest during the period when 

 the crop was drawing most heavily on them. The incubated samples 

 with ammonium sulphate were on the average about 100 per cent higher 

 than the samples without it. Therefore, it seems that an application of 

 some nitrogenous fertilizer would be beneficial. An interesting point in 

 connection with this plot is that after being plowed for wheat about 

 August 26, the moisture content stayed up whereas the moisture con- 

 tent of the unplowed wheat plot went down rapidly. 



TABLE IV.— Series 2 West 



Date 



Plot 10 CI. & Tim. 



Mois- 

 ture 

 Per 

 Cent 



Nitrates — Parts 

 per Million 



Fresh 



Incubated 



I 



II 



Plot 11 Corn 



Mois- 

 ture 

 Per 



Cent 



Nitrates — Parts 

 per Million 



Fresh 



Incubated 



I 



II 



Plot 12 Wheat 



Mois- 

 ture 

 Per 



Cent 



Nitrates — Parts 

 per Million 



Fresh 



Incubated 



II 



Apr. 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 



29.62 

 26.37 

 26.02 

 16.71 

 12,72 

 11.61 

 16.40 

 11.96 

 9.97 

 16.41 

 12.98 

 11.01 

 23.25 

 22.09 



17. 



3.18 

 2.16 

 3.46 

 2.42 

 4.36 

 4.63 

 8.94 

 9.12 

 9.26 

 7.47 

 5.31 

 4.76 

 3.33 

 4.62 



13.84 

 10.42 

 22.69 

 14.06 

 18 59 

 19.20 

 22.46 

 21 55 

 18.22 

 21.08 

 20.37 

 15.30 

 14.04 

 9.61 



5.00 17.25 27.83 



20.16 

 25.75 

 29.74 

 23.28 

 29.73 

 32.34 

 36.30 

 32.64 

 35.20 

 33.60 

 30.67 

 21.24 

 21.46 

 17.46 



27.79 

 27.27 

 25.15 

 20.96 

 19.37 

 19.71 

 22.11 

 19.49 

 17.31 

 21.34 

 16.77 

 13.89 

 24.38 

 22.41 



6.24 

 6.59 

 6.84 

 12,41 

 16.64 

 17.29 

 25.45 

 21.17 

 18,42 

 24.26 

 23.13 

 24.09 

 10.88 

 8.90 



13.30 

 20.08 

 27.92 

 29.62 

 39.84 

 43.73 

 41.53 

 42.32 

 37.68 

 37.98 

 30.16 

 30.40 

 20.77 

 17.44 



14.86 

 23.26 

 29.96 

 27,90 

 40,09 

 48,69 

 44,89 

 42,49 

 44.70 

 40.22 

 35.43 

 35.12 

 25.19 

 23,39 



27.22 

 24.50 

 23.91 

 15.03 

 13.78 

 12.76 

 16.53 

 13.01 

 11.56 

 17.18 

 12 22 

 10^87 

 25.05 

 23.46 



5.71 

 2.01 

 2.52 

 1,48 

 7.64 

 7.69 

 14.02 

 13.16 

 13.43 

 10.81 

 7.03 

 6.84 

 2.76 

 2.89 



10.75 

 9.28 

 21.16 

 17.76 

 18.73 

 19,26 

 22,57 

 21.95 

 21.71 

 19.82 

 18.22 

 16.74 

 10.45 



21.28 15.88 31.56 



34.01 



17.65 



13.04 

 25.60 

 27.88 

 28.52 

 27.49 

 33.05 

 38,40 

 40.21 

 39.50 

 35.66 

 34.57 

 30.19 

 21.55 

 13.69 



29.24 



18—27933 



