616 EXPERIMENT STATION RECORD. 



dried soil, or from 0.203 to 0.653 per cent of the total soil nitrogen. Liliewise, 

 the proportion of nitric nitrogen is small, namely, from 0.00005 to 0.00269 per 

 cent of the oven-dried soil, or from 0.02 to 1 per cent calculated upon the total 

 soil nitrogen. This leaves about 99 per cent of the total soil nitrogen in the 

 form of organic compounds. The proportion of amido nitrogen is quite con- 

 siderable, ranging from 26.99 to 33.83 per cent calculated upon the nitrogen 

 obtained in solution by boiling with hydrochloric acid. Among the nitrogenous 

 compounds, contained in the rest of the acid-soluble nitrogen, the monamino 

 acids and diamino acids were found to be present in considerable quantities." 



Influence of various factors on decomposition of soil organic matter, 

 S. L. JoDiDi and A. A. Wells (Iowa 8ta. Resciuxh Bui. 3. pp. 135-15 'i, pis. 2, 

 figs. 2). — Taking the production of carbon dioxid of the soil as a convenient 

 measui'e of the rate of oxidation of humus, the authors undertook a series of 

 determinations of combined carbon dioxid and of free carbon dioxid and 

 oxygen in soils of plats differently treated and cropped. The combined carbon 

 dioxid was determined by a modification of the method of Mulder, Stolba, and 

 Kolbe. The free carbon dioxid and oxygen were determined in the soil air by 

 means of the Orsat apparatus. The soil air Avas obtained by driving an iron 

 tube f in. in diameter and having perforations in its lower end into the soil 

 to the desired depth, then drawing the desired amount of air through the Orsat 

 apparatus by means of an aspirator. 



Determinations of both carbon dioxid and oxygen were made once a day on 

 22 plats during April to August, 1910. The average i>ercentage of oxygen in 

 the soil atmosphere for all of the plats during this period was 20.51 per cent. 

 The aA'erage amount of carbon dioxid was 0.252 per cent. These figures indi- 

 cate that tlie total percentage of carbon dioxid and oxygen in the soil atmos- 

 phere is about the same as in the air. 



It was found that an increase of moisture and temperature as well as tillage 

 operations was followed by a more rapid decomposition of the organic matter 

 in all of the plats. There was, however, wide A^ariation in rapidity of decom- 

 position of the organic matter and it was apparently determined more by the 

 chai'acter than the amount of organic matter present. For example, a plat 

 which contained a high percentage of humus derived from peat showed the 

 lowest amount of carbon dioxid in the soil atmosphere. 



The movement of nitric nitrogen in soil and its relation to nitrog'en fixa- 

 tion, R. Stewart and J. E. Greaves (Utah Sta. Bui. IL'i, pp. 181-19 Ji; abs. in 

 Science, n. ser., 35 (1912), No. 893, p. 228). — This is a paper presented at the 

 Washington meeting of the Society of American Bacteriologists in December. 

 1911, summarizing studies made at the Utah Station during the past 8 

 years on the influence of irrigation upon the production and movement 

 of nitric nitrogen in the soil (E. S. R., 22, p. 617), and stating that these 

 investigations, which have been conducted on what is considered soil ideally 

 adapted both chemically and bacteriologically to support rapid bacterial action, 

 have shown an amount of nitric nitrogen to a depth of 10 ft. not exceeding 

 300 lbs. per acre — much less than has been foimd in other western soils and 

 attributed to fixation in place of atmospheric nitrogen. 



From an examination of the analytical data for soils containing very high 

 percentages of nitrate reported by W. P. Headden (E. S. R., 23, p. 221; 25. 

 p. 814), the authors conclude that there is a certain parallelism between the 

 accumulation of nitric nitrogen and chlorin, indicating a common origin. 

 " This origin is indicated by the deposits occurring in the country rock, such 

 as noted in the shales of Colorado, the sandstones of Idaho, and the rocks of 

 southern Utah and Nevada" (E. S. R., 26. p. 226). Although the authors do 

 not maintain " that nitrogen fixation may not take place to a certain extent 



i 



