SOILS FERTILIZERS. 515 



solid auci liquid media, and tlie effect upon tlie latter of the antagonism of 

 symbiotic action, as tlie case might be. Marked instances of antagonism and 

 symbiosis were found, and the production of toxins was demonstrated." 



Investigations on protozoa in relation to the factor limiting bacterial 

 activity in soil, T. Goodey {Proc. Roy. Soc. [London], Ser. B, 88 {1915), No. B 

 606, pp. 437-456, figs. 8).— From the results of further investigations (B. S. R., 

 25, p. 817) of the Russell and Hutchinson hypothesis (E. S. R., 24, p. 621) it 

 is concluded that " the protozoa, including ciliates, amoebre, and flagellates 

 added to the soil have not been able to act as a factor limiting bacterial activity 

 in the soil. Inferentially, therefore, the ciliates, amoebae, and flagellates ob- 

 tainable from ordinary soil under cultural conditions do not function as the 

 limiting factor." 



Further investigations on the biological absorption of phosphoric acid in 

 the soil, A. Dushechkin {Zhiir. Opytn. Agron. (Russ. Jour. Expt. Landw.), 15 

 {1914), No. 6, pp. 467-500, figs. 6; ahs. in, Ghem. Ahs., 9 {1915), No. 8, p. 1085).— 

 In further studies of the biological absorption of phosphoric acid in soils (E. 

 S. R., 27, p. 216), the experiments were extended to include the effect of water 

 content and light and to determine the connection between denitrification and 

 phosphoric acid absorption. 



It was found that the biological absorption of phosphoric acid in soils in- 

 creased with increasing water content. With time, decomposition products ac- 

 cumulated in the soil which had a dissolving effect on the phosphoric acid and 

 diminished the absorption process. Nitrate additions increased the phosphoric 

 acid absoi-ption only with medium moisture content (25 per cent). The absorp- 

 tion was most marked under conditions favoring denitrification. With a higher 

 moisture content (35 per cent) it was stronger in light, but with a lower 

 moisture content (25 per cent) it was favored by darkness. 



The comparative effect of phosphates and sulphates on soil bacteria, E. B. 

 Fred and E. B. Hart {Wiscotisin 8ta. Research Bui. 35 {1915), pp. 35-66, figs. 

 6). — Investigations on the influence of phosphates and sulphates in the form of 

 chemically pure salts upon the activities of soil bacteria, as measured by rates 

 of ammonification with pure and mixed cultures in soil and solution, by rates 

 of carbon dioxid evolution, and by plate counts to determine if the fertilizing 

 effect of these substances can be explained in part by the promotion of bac- 

 terial action are reported. The soil used was Miami silt loam. 



It was found, in general, that the addition of mineral fertilizers to soils 

 caused an increase in ammonification, carbon dioxid evolution, and total num- 

 ber of bacteria. Monobasic potassium phosphate, precipitated calcium phos- 

 phate, and the sulphates of potassium and calcium all increased ammonifica- 

 tion in solution more or less, while tricalcium phosphate was ineffective. The 

 action of monobasic potassium phosphate as compared with that of potassium 

 sulphate is taken to indicate that the potassium ion does not materially In- 

 fluence ammonification. Monobasic potassium phosphate caused an enormous 

 increase in numbers of bacteria in solution, followed by a rise in ammonia pro- 

 duction, which was not, however, in proportion to the number of bacteria. 



All the phosphates used Increased the number of soil bacteria, particularly 

 dibasic potassium phosphate. Dibasic potassium phosphate and tricalcium 

 phosphate also stimulated ammonification in soil. Calcium sulphate, potassium 

 and calcium phosphates, and ammonium, magnesium, and potassium sulphates 

 all stimulated more or less the evolution of carbon dioxid from the soil. 



" The results of this work, as a whole, suggest that possibly the increased 

 crop production of a soil resulting from the application of soluble phosphates is 

 in part due to the promotion of bacterial activity. . . . The sulphates, although 



