January 7, 1916] 



SCIENCE 



23 



responsible for tlie production of tlie nitrates 

 noted in the niter spots of the affected soils of 

 the arid west and their presence there is only 

 incidental and of no more economic impor- 

 tance than their more ahundani occurrence in 

 other normal " niter "-free soils of the arid 

 regions. The nitrates present in the " niter 

 spots " are the direct result of the leaching 

 and concentrating action of the ground water 

 upon the nitrates preexisting in the country 

 rock adjacent to or underneath the soil of the 

 affected area. 



The nature and source of the color present 

 in these spots is of no economic importance 

 whatever except as evidence in support of one 

 or the other of the theories regarding the 

 origin of the nitrates themselves. The azoto- 

 bacter are in no way concerned in the produc- 

 tion of this color. In the normal dry farm 

 soils of Utah the maxinnun fixation of nitro- 

 gen by the non-symbiotic organisms is greater 

 than in the niter soils, yet these soils are free 

 from nitrate accumulation and the color and 

 other characteristics likewise are absent. 



and decomposing action (double decomposi- 

 tion) of the nitrates of sodium and potassium 

 upon the old organic matter or humus already 

 occurring in the shale and sandstone is suffi- 

 cient to account for the production of the color 

 in these " niter spots." 



The nitrates of sodium and potassium do 

 have a solvent action on organic matter as 

 already demonstrated.'^" A rich greenhouse 

 soil already abundantly supplied with nitrate 

 was extracted with water for 24 hours as in 

 the official humus determination. A highly 

 colored solution resulted. An aliquot portion 

 on evaporation to dryness and ignition gave a 

 loss of 0.57 per cent. The soil was then ex- 

 tracted with the various soluble salts of 

 sodiiun, potassium, magnesium and calcium. 

 The variation in intensity of the color was 

 very pronounced with the extract of the differ- 

 ent salts. How can this fact be best con- 

 veyed to the reader is an important question 

 which arose ? The following data were obtained 

 on evaporation and subsequent ignition of an 

 aliquot portion of the extract : 



The color is due to the solvent and decom- 

 posing action of the nitrates upon the old or- 

 ganic matter or humus in the soil. The source 

 of the old organic matter, like the nitrates, 

 may be found in the adjacent shales which as 

 already pointed out are coal- and oil-bearing. 

 Some of the most important coal deposits of 

 Utah and Colorado are found in these shales 

 and sandstones. As a result the ordinary 

 shale contains more or less organic matter. 

 As an illustration, the analysis of twelve 

 samples of shales from near Grand Junction, 

 Colorado, gave an organic nitrogen content of 

 1,840 pounds per two million pounds of shale. 



The assumption of the hydrolyzing action of 

 sodium nitrate and the subsequent humifica- 

 tion of the organic matter of the soil to form 

 the brownish colored organic compounds is as 

 unnecessary as it is untenable. The solvent 



Notwithstanding the confessedly crude 

 method of conveying a conception of the va- 

 riation in color extracted by the several salts, 

 considering the results as a whole two im- 

 portant facts are evident: (1) the solvent 

 action upon the organic matter of the salts of 

 sodium and potassiimi and (2) the repressive 

 action of the salts of magnesium and calcium. 

 The solvent action is very pronounced in the 

 cases of sodium and potassium carbonate and 

 the repressive action is very pronounced in 

 the case of the salts of calcium. How may 

 we interpret these data? 



The aqueous extract alone dissolved some 

 colored organic matter due undoubtedly to the 

 fact that the soil itself contained several hun- 

 dred parts per million of nitrate. Likewise, 



10 Stewart and Peterson, Jr. Am. Soo. Agron., 

 Vol. 6, p. 247, 1914. 



