SOILS FERTILIZERS. 17 



R., IS, p. 102o) on the changes in the nitrogen content of a number of clay loam 

 soils under the influence of continuous cropping in a general system of farm 

 management. Determinations of nitrogen in the cropped soil and in similar vir- 

 gin soil are reported. 



The results show in general that the largest loss of nitrogen has occurred in 

 those soils which ordinarily contain a rather large percentage of nitrogen. In 

 16 out of 21 cases i^ which the virgin soil contained 0.2 per cent of nitrogen 

 or over the loss of nitrogen above that removed by crops, probably due chiefly 

 to denitrification and leaching, exceeded 500 lbs. per acre. In 21 out of 2G 

 cases in which the virgin soil contained less than 0.2 per cent of nitrogen the 

 loss of nitrogen was less than 500 lbs. per acre. The average losses were 20.1) 

 per cent of that removed by ci-ops in 1907 and 22.3 per cent in 1906. The loss 

 of nitrogen above that removed by crops was greater when the soil was man- 

 ured than when no manure was applied. "This seems to indicate that the 

 nitrogen added in the form of manure, as ordinarily applied, does not accumu- 

 late In the soil, and suggests the desirability of a very careful study of the 

 methods of applying farmyard manure to determine whether it should be 

 applied in very small quantities annually, or larger amounts at intervals of 4 to 

 G years, as is the customary practice." 



The feeding of plants by the free living' nitrogen-fixing bacteria of the soil, 

 A. Koch et al. (Jour. Landtv., 55 {1901), No. 4, pp. 355-J/16, pis. .3; abs. in 

 Deut. Landw. Prcsse, 35 (1908), No. 6, p. 57; Chem. ZentbL, 1908, I, No. 5. pp. 

 J,80, J,81; Jour. Chem. Soc. [London], 9If (1908), No. 5J,3, II, pp. 56, 57: Jour. 

 Soc. Chem. Indus., 27 (1908), No. 9, p. J,59 ; CenthJ. Bakt. [etc.], 2. Abt., 21 

 (1908), No. 13-1 Jf, pp. Ji35-Ii37). — These investigations have been reviewed from 

 another source (E. S. R., 19, p. 318). 



On fixation of nitrogen in cultivated soils, H. Warmbold {Ccntbl. Bakt. 

 [etc.], 2. Abt.. 20 (1907), No. J,-5, pp. 121-126) .—Thiii is a reply to criticism by 

 Pfeiffer and his collaborators (E. S. R.. IS, p. 617) of a previous article by the 

 author, in which data were reported indic;iting a chemical fixation of nitrogen 

 in sterilized soils. In further experiments with the same samples of soils no 

 gain was observed under such conditions. On the other hand, a decrease in 

 percentage of total nitrogen was observed in all cases. The extent to which 

 these apparent gains or losses are due to analytical errors is discussed. 



Fixation of nitrogen by certain hyphomycetes living in dead plants, H. 

 Froehlicii (Jahrb. IT'/.s-.s. Bot. \ I'riiiyslieini], J/o (1907), No. 2, pp. 256-302, figs. 

 3). — Studies of nitrogen fixation in inire cultures of Alternaria tenuis, Macro- 

 fsporiuvd commune, Hormodcudron cladosporioides, and Chidosporivm herbarum, 

 derived from dead stems and leaves of various trees and herbaceous plants are 

 reported which showed that these organisms, which occur widely distributed 

 in plant remains, can grow normally on substrata to which no nitrogen com- 

 pounds have been intentionally added. Careful determination of the nitrogen 

 balance indicates that all four of the organisms assimilate free nitrogen from 

 the air. 



Under the cultural conditions of these experiments the relative rates of fixa- 

 tion per 100 cc. of culture solution were as follows: M. commune 3.70 mg. of 

 nitrogen, .4. tenuis 3.34 mg.. C. herbarum 2.26 mg., and H. cladosporioides 1.93 

 mg. The period covered by the different experiments varied from 39 to 42 days. 

 The maximum nitrogen increase ob.served was 4.5 mg. in a culture of Macro- 

 sporium, the smallest, 1.16 mg., in a culture of Hermodendron. The nitrogen 

 content of the dry matter produced (100 to 200 mg.) was relatively low, but 

 varied with the different cultures. In general it was somewhat less than 1 per 

 cent. All of the organisms required oxygen for their growth and are obligate 

 aerobic organisms. Ilormodendron and Cladosporium were able to grow at 



