SOILS FERTILIZERS. 819 



The conclusions reached are hi brief as follow.s : 



"Many cultivated soils of Colorado contain a vigorous nitrifying flora 

 capable of transforming ammonical nitrogen into nitrate nitrogen. Both 

 . . . normal soils and those in the incipient stage of the niter trouble possess 

 this power in a very marked degree. 



" Compared with soils from twenty-two other localities outside of the State, 

 the Colorado soils examined are very superior in nitrifying efliciency. The 

 nitrifying efficiency of Colorado soils bears an inverse relation to that of the 

 foreign soils when referred to ammonium sulphate, ammonium carbonate, and 

 dried blood as the nitrltiable substances. Colorado soils produced their highest 

 average grains in nitric nitrogen from (NH4)2SOs the next largest from 

 (NH4)2C03, and the lowest from dried blood. The foreign soils produced their 

 largest average yields in exactly the reverse order. The nitrifying flora of the 

 Colorado soils is distinct from that found in the majority of the foreign 

 samples; it is either made up of entirely different organisms, or, if the same 

 organisms, they behave like different strains. 



" Excessive nitrates do not appear to interfere seriously with nitrification 

 provided the chlorin is low. Excessive chlorin, with or without excessive 

 nitrates, inhibits nitrification. Active nitrification takes place in the brown 

 crust from the niter spots provided the chlorin is not excessive. The sample of 

 raw adobe clay examined was deficient in nitrifying efficiency. 



" The results of this study together with those of . . . two previous investi- 

 gations justify the position that the excessive nitrates present in certain 

 Colorado soils have resulted from the combined action of nitrogen-fixing, am- 

 monifying, and nitrifying organisms." 



An examination of some more productive and some less productive sec- 

 tions of a field, T. L. Lyon, J. A. Bizzell, and H. J. Conn {'New York Cornell 

 ma. Bui. 338 (1913), pp. 51-115, figs. i2).— This bulletin reports physical and 

 chemical examinations of the soils of productive and unproductive sections of 

 the same field as well as studies of the bacterial flora of the soils. 

 _^ Aeration increased, temporarily, the formation of nitrates and the produc- 

 tiveness of the poorer soil beyond that of the better. When the whole area 

 was divided into small plats and cropped with millet for four years, there was 

 a fairly constant relation in the yields of both productive and unproductive 

 plats. 



Neither type of plat was distributed with any definite relation to the topogi*aphy 

 of the area. Mechanical analyses of the soils showed that the texture under- 

 went a gradual change from the upper to the lower part of the area, but there 

 was no constant relation between the productiveness of the plats and their me- 

 chanical composition, and chemical analyses showed no great difference in the 

 inorganic constituents. 



The soils in the lower yielding plats were more compact than those in th« 

 higher yielding plats. " The more compact condition of the soil was less favor- 

 able to the formation of nitrates, and thus the qualities of productiveness, com- 

 pactness, and rate of formation of nitrates are correlated." It is therefore con- 

 cluded "that a too compact condition of the soil is the cause of the lessened 

 productiveness of certain small sections of this soil for the growth of certain 

 crops." 



Conclusions of a general nature from the studies of the bacterial flora of 

 these soils are as follows: The flora of soil is quite different from that of 

 other natural media, consisting primarily of strict aerobes that do not produce 

 spores, the majoritiy of which liquefy gelatin very slowly and grow but poorly in 

 the ordinary bacteriological media. Certain types of bacteria may occur 

 throughout the year, growing in winter and in summer alike, while others grow 



