CTTLORTDR AND i^TT.PTTATES. 



21 



It ^\ ill be seen that the nitrifiers and especially the nitrate bacteria 

 develop quite well in solutions. It should be noted that the only 

 samples that failed to produce nitrites were those taken at 6-inch, 

 12-inch, and 18-inch depths from plat 220, which failed to nitrify in 

 soil. (See fig,. 9.) This soil, however, ])roduce(l niti-ates quite readily. 

 This suo;orests the ])ossibility that the lack of nitrification in this soil 

 may be due to lack of nitrite bacteria. 



CHLORIDS AND SULPHATES. 



In alkali studies it is recognized that as a rule the chlorid type is more 

 injurious to ordinary farm crops than the sulphate type. Further, in 

 some investigations in the soils of the arid regions it has been found 



Fig. 14.— Diagram showing the relation between the quantity of alkali and the nitrification in samples of 

 soil from plats ISO, 190, 170, 150, 100, 160, 110, and 120, Tnickee-Carson Experiment Farm. Samples 

 taken from dei>ths of to li inches. 



that high nitrates correlate with the sulpliate type, while low nitrates 

 are usually associated with the clilorid type. It was thought, tliere- 

 fore, that it would be of interest in connection with this work to study 

 the relation of clilorids and sulphates to the nitrifyhig power. 



In ])lotting these curves the different j)lats are arranged in such 

 an order that the nitrification of ammonium sul])hate by the dif- 

 ferent sam])les, which is the index of the difference of their powers 

 of nitiification, forms an ascending series. Four diagrams are jire- 

 sented (figs. 14 to 17), one for each dej)th from which sam])les of soil 

 were taken. Figure 14, re])resenting tlie surface samples, shows no 

 relation between the concentration of soluble salts and nitrifying 

 power. Figures 16 and 17, re])resenting the deeper samples, are 



211 



