28 SOILS OF THE TRUCKEE-CARSON IRRIGATION PROJECT. 
TasLe V.—Efect of calcium sulphate upon nitrification in samples of soil from plat 
520, Truckee-Carson Experiment Farm, representing good soil conditions. Incubated 
15 days at 28° C. / 
NO CALCIUM SULPHATE ADDED TO SAMPLES. 
_ Nitrogen as nitrite (parts per | Nitrogen as nitrate (parts per 
E million). million). 
No. of | Depth of| 
plat. soil. | 
| | Original.| Final. Gain. | Original. | Final. Gain. 
Inches. 
320 0-6 1.4 4.00 2.60 3.84 | 64 76. 80 
6-12 1.5 1.20 — .30 18.24 | 76.80 58. 56 
12-18 -0 1.60 1.60 15.90 5.00 | —10.90 | 
18-24 -8 1.40 60 UGL8O" | 0. 00 —15.36 
{ 
WITH 2 PER CENT CALCIUM SULPHATE ADDED TO ALL SAMPLES. 
320 0-6 
| : 
1.4 5.00 3.60 | 3.84 | 81.60 | 77.76 | 
(ail oe eas 1.68 13 | 18.24 | 76.80 | 58.56 | 
12-18 | 0 1.82 | 1.82 | 15.90 cay ears | 
18-24 | 8 | 
{ 
-60' 7) = .20 | 15536 -00 | —15.36 
The gain in nitrates, or the nitrifying power of these samples of 
soil, is shown in figure 18. 
These experiments on nitrification indicate that the difference in 
productiveness is not due to a suspension of nitrification, and also 
that it is not due to the presence of sodium carbonate, as the addition 
of calcium sulphate to the samples had absolutely no effect; the 
treated and untreated samples could really be considered duplicates. 
It would seem also that the infertility or the lack of decay of organic 
substances is not due to lack of air. It might be argued that lab- 
oratory conditions were not such as would favor the compacting or 
cementing of the samples, yet it must be remembered that the corn- 
field containing plats 300, 310, and 320 was kept well cultivated and 
no crust was allowed to form during the growing season. Tables 
VI and VII show the nitrification of the different samples in Wino- 
gradsky and Omelianski’s media. 
TaBLeE VI.—Mitrite formed from ammonia by samples of soil from plats 330, 340, and 
3850, Truckee-Carson Experiment Farm, in medium for nitrite bacteria. Incubated 
at 28° C. 
Nitrite | Nitrite 
_ formed in | formed in | Charac- ' 
Be f Pepin t 5days | 10days ter of 
JEN * | (parts per | (parts per | _ soil. 
million). | million). 
Inches. . 
330 0-6 0.0 | 4.8 Poor. Ps 
6-12 A | .0 4 
12-18 a0 .0 ; 
18-24 0 0 4 
340 0-6 9.6 10. 4 Do. : “2 
6-12 12.8 12.8 , 
12-18 12.8 12.8 . = 
18-24 0 12:2 = 
350 | 0-6 .0 Trace. | Good. . 
| 6-12 0 4.8 
12-18 .0 .0 
18-24 .0 | .0 
211 
