SOILS FERTILIZEES. 719 



These results are taken to indicate that tlie soils should be limed, but that the 

 calcium carbonate should contain as little magnesium carbo'iate as possible. 

 Dried blood is considered i) referable to ammonium salts as a fertilizer. It is 

 recommended that optimum moisture conditions (20 to 40 per cent moisture) 

 be maintained in the soil, that surface cultivation be frequent, and that cogon 

 lands be not burned off. 



Nitrogen content of the humus of arid soils, F. J. Alway and E. S. Bishop 

 {U. S. Dcpt. Agr., Jour. Afjr. Research, 5 (WIG), No. 20, pp. 909-916).— In this 

 contribution from the Minnesota Experiment Station, the work of others bear- 

 ing on the subject is brieflj^ reviewed, methods of humus nitrogen determina- 

 tion in soils are discussed, and the results of determinations of humus and 

 humus nitrogen in 16 virgin and cultivated arid California soils, made by the 

 authors in 1911 while at the Nebraska Station, are reported. 



" Of the 16 samples only five show as high as 10 per cent of nitrogen in the 

 humus. For the 6 samples of virgin soil the average is 8.5 per cent, with a 

 maximum of 12 and a minimum of 4 per cent. For the 10 of cultivated soils 

 the corresponding data are 8.1, 11.8, and 5.6 per cent, respectively. The max- 

 imum possible percentages of nitrogen in the humus — the relation of the total 

 nitrogen to the humus — ranged from 5.5 to 19.6 per cent, with an average of 

 13.1." These results are taken to " confirm the work of Hilgard that high per- 

 centages are to be found in the arid, but not in the humid soils. This high 

 nitrogen content of the humus, however, does not appear so general in the arid 

 soils as to serve as an at all reliable means of ideatification." 



Investigations on ammonia adsorption by soil, L. Pinner (Kiihn Arch., 6 

 {1915), pt. 1, pp. 153-238, fi(js. 5; abs. in Internal. Inst. Agr. [Rome], Mo. Bui. 

 Agr. Intel, and Plant Diseases, 6 {1915), No. 10, pp. 1304, 1305).— The history 

 and theory of the adsorption of gases by soils and other materials are reviewed 

 in some detail, and exi^eriments with a number of German soils and with red 

 soils from other countries are reported. The pui'pose was to determine the 

 adsorptive power of the soils for ammonia when treated with ammonia solution, 

 gaseous ammonia, and ammonium chlorid solution. The ammonia adsorption 

 was determined gravimetrically and volumetrically. Parallel experiments were 

 conducted with charcoal and permutite. 



It was found that no conclusive parallelism existed between ammonia adsorp- 

 tion and the mechanical and chemical properties of the soils. The ammonia 

 adsorption values for the native soils were parallel to their hygroscopicity 

 values. The red soils showed a wider and more irregular relation between 

 hygroscopicity and adsorption of gaseous ammonia. Ammonia adsorption by 

 soils was similar to that by charcoal. The greatest gas adsorption occurred 

 within a few minutes and became constant only after some hours. Ammonia 

 adsorption was greater by soils retaining some hygroscopic moisture than by 

 dried soils, but not as great as by dried soils and water together. Part of the 

 adsorbed ammonia gas was retained by the soils even when aerated for some 

 weeks. While certain relations existed between the adsorption of ammonia 

 from ammonia solution or ammonium chlorid solution and the adsorption of 

 gaseous ammonia, no parallelism was proved. Ammonia adsorption by soil from 

 ammonium chlorid and from ammonia solution also differed. An increase in 

 the quantity of ammonium salt solution used caused a decrease in ammonia 

 adsorption by all the soils. 



It is concluded that ammonia adsorption varies considerably on account of 

 the complex nature of the soil, thus practically preventing the formation of a 

 theory applicable to all kinds of soils. However, the Freundlich theory that 

 adsorption is a surface condensation process is considered the most probable. 



