22 



SCIENCE 



[N. S. Vol. XLIII. No. 1097 



process in other soils and thus solve the most 

 important problem in American agriculture. 



These niter spots are characterized by the 

 following conditions: (1) The presence of 

 large quantities of nitrates; (2) the inevitable 

 presence (usually larger quantities) of other 

 soluble salts such as the chlorides and sulphates 

 of sodium, potassiiun, calcium and magne- 

 simnj (3) the absence of appreciable quantities 

 of soluble carbonates; (4) the presence of a 

 dark brown color or stain; (5) the formation 

 of a hard crust on the surface of the soil; (6) 

 underneath the crust there is a layer of dry 

 dust with fine alkali salt crystals which gives 

 an ash-like or mealy condition of the soil; (7) 

 beneath the ash the soil is moist, sticky and 

 glistening. These niter spots usually occur in 

 cultivated soil after it has been irrigated for 

 a few years. But they likewise occur in the 

 non-irrigated and non-arable soils of the moun- 

 tains wherever moisture conditions are favor- 

 able to the concentration of the salts. 



Over four hundred samples of the country 

 rock were collected from the original rock ad- 

 jacent to the soils in the affected areas and 

 these were analyzed for nitrates and other 

 soluble salts. These data form a basis for the 

 theory developed by us. The soils most af- 

 fected are those derived from the Mancos 

 shales of the cretaceous as well as from the 

 shales and sandstones of the tertiary de- 

 posits. 



Sufficient evidence has been presented by us 

 to show conclusively that these nitrate accu- 

 mulations are the direct result of the concen- 

 trating and leaching action of the irrigating 

 water upon the nitrates already existing in the 

 original country rock adjacent to and under- 

 neath the affected soils. Briefly summarized, 

 our case rests upon the following evidence: 



(1) Highly productive, irrigated soils rich in 

 organic matter, free from alkali, are also free 

 from niter spots, or nitrate accumulations. 



(2) Alkali and nitrate-free soils, under similar 

 climatic conditions, irrigated with water from 

 the same river, geographically adjacent, but 

 derived from different geological series, have 

 been cultivated and irrigated for ten times 

 as long as the niter soils, yet are free from 



nitrate accumulations. (3) The total alkali 

 salts of any given spot fluctuate from year to 

 year; the nitric nitrogen and total salts, as 

 measured by the chlorine content, increase and 

 decrease in quantity in the same general ratio. 

 The same influences must be at work on both. 

 (4) The amount of chlorides and sulphates 

 present are enormous in quantity and are suffi- 

 cient in themselves to render the soil non- 

 productive. Thus in a characteristic spot a 

 noted increase of nitric nitrogen in four years 

 of 621 pounds was accompanied by an in- 

 crease of 128 tons of chlorine and 315 tons of 

 total alkali salts. (5) There is no record of 

 " niter spots " free from these other salts ; the 

 nitrates and other alkali salts must there- 

 fore be associated in some manner. (6) Lip- 

 man^ has shown conclusively that alkali salts 

 not only do not have a stimulating effect on 

 the production of nitrates in alkali soils, but, 

 on the contrary, nitrification is inhibited. (7) 

 The fixation of atmospheric nitrogen in the 

 non-irrigated soils^ of Utah is much greater 

 than in the niter soils, yet the nitric nitrogen 

 content of the latter is only normal, being 

 less than sis parts per million. (8) Niter 

 spots, possessing all the characteristics, occur 

 in the virgin state in the uncultivated and non- 

 arable areas of the near-by hills wherever the 

 water conditions are such as to cause a leach- 

 ing and concentrating action on the soluble 

 salts, including the nitrates preexisting in the 

 rock itself. (9) There are large quantities of 

 nitrates in a widely disseminated form, oc- 

 curring in the country rock adjacent to and 

 underneath the affected soils. (10) These 

 nitrate accumulations although not of any 

 commercial economic importance, so far as 

 known, because of their wide distribution, are 

 more than sufficient, being greater in quantity 

 than those of Chili, to account in full for the 

 nitrate accumulations observed in the alkali 

 soils. 



This evidence leads us to the inevitable con- 

 clusion that the non-symbiotic bacteria are not 



sLipman, Central f. Bkt., Abt. II., Bd. 33, s. 

 305. 



9 Greaves, Central f. BTct., Abt. 11., Bd. 41, p. 

 444. 



