26 SOILS OF THE TKUCKEE-CARSON IRRIGATION PROJECT. 



to produce toxic effects, and a lack of mineral plant food in the virgin 

 soils is almost out of the question. 



Both soils are low in organic matter, as are all arid soils. Good 

 soil management in other somewhat similar regions would indicate 

 that the addition of organic matter to these soils in the form of barn- 

 yard manure or green manure should produce beneficial physico- 

 chemical effects, and such treatments have been applied somewhat 

 extensively as a matter of experiment during the last two or three 

 years. The poor soil apparently has not been benefited to a noticea- 

 ble degree. The good soil has been somewhat improved, although 

 even here the improvement has not been striking. A minute field 

 examination of these good and poor spots a year or more after they 

 had received applications of organic matter revealed a remarkable 

 difference; all traces of the organic material had disappeared from 

 the fertile spots, while the larger part of the manure added to the 

 infertile spots was in an almost perfect state of preservation. Another 

 peculiar difference was that in the poor spots, at depths of 6 to 28 

 inches, an irregularly distributed, dark-colored, foul-smelling layer 

 was found, undoubtedh' due to the presence of a peculiar organic 

 decomposition product, while such a layer was never found associated 

 with good soil. It should not be inferred from this description that 

 this black layer was found only where organic matter has been added 

 as a treatment; it was quite generally distributed through these 

 infertile soils and is presumably due to the decay of such material as 

 was turned into the soil when it was first reclaimed, such as sagebrush, 

 greasewood, rabbit brush, and other desert plants, together with the 

 roots of these plants which have been accumulating for long periods 

 of time. Laboratory samples showed that this black substance was 

 easily oxidized, for when a sample was taken to the laboratory, dried, 

 and subsequently moistened for physiological experiments, all traces 

 of the black color and peculiar odor disappeared. 



These unusual conditions of the decay of organic matter are neces- 

 sarily somewhat closely associated with impro})er bacteriological 

 conditions; that is, the improper utilization of organic fertilizers is 

 due either to an improperly balanced or incomplete bacterial flora 

 or to phA'sical or chemical conditions preventing the i)erforinance of 

 the normal activities of the bacteria })resent. 



Titrations of some of the aqueous extracts indicated that sodium 

 carbonate (black alkali) was present in the poor soils but not in the 

 good soils. It was also apparent that calcium sulphate and gypsum, 

 when applied in large quantities, ])roduced a decided effect in floc- 

 culating the finely divided or colloidal clays. Samples were collected 

 with a sterile spatula from the sides of freshly dug holes and ])laced 

 in sterile containci's. Portions of these samples were inoculated into 

 211 



