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SOILS OF THE TRUCKEE-C ARSON IRRIGATION PROJECT. 



Table V. — Effect of calcium sulphate upon nitrification in samples of soil from plat 

 S20, Truckee-Carson Experiment Farvi, representing good soil conditions. Incubated 

 15 days at 28° C. 



NO CALCIUM SULPHATE ADDED TO SAMPLES. 



WITH 2 PER CENT CALCIUM SULPHATE ADDED TO ALL SAMPLES. 



The gain in nitrates, or the nitrifying power of these samples of 

 soil, is shown in figure IS. 



These experiments on nitrification indicate that the difference in 

 l)roductiveness 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 sam])les in Wino- 

 gradsky and Omelianski's media. 



Table VI. — Nitrite formed from ammonia by samples of soil from plats .180, 340, and 

 350, Truckee-Carson Experiment Farm, in medium for nitrite bacteria. Incubated 

 at 28° C. 



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