1917] SOILS FERTILIZERS. 513 



Clienucal, bacteriological, and agricultural investigations on an experi- 

 mental cultivated soil, K. Diem (Meded. Deli-Proefstat. Medan, 9 {1916), No. 5, 

 pp. 143-176, pis. 7). — Experiments on the influence of methods of cultivation, of 

 physical, mechanical, and chemical properties of tobacco soils, and of mixing 

 the ashes of weeds with soils on the height and green weight of tobacco plants 

 are reported. 



No relation was found to exist between the green weight or height of plant 

 and the soil properties. The intermixing of considerable amounts of weed 

 ashes with the soil also had no appreciable influence on the stand of tobacco. 



Influence of pine resin and tannin on the nitrogen economy and on the 

 physical properties of the soil, A. Koch and Alice Oet-sner (Centbl. Bakt. 

 [etc.], 2. AM., Jf5 (1916), No. 1-5, pp. 107-118; abs. in Jour. Chem. Sac. [Lon- 

 don], 110 (1916), No. eJfJi, I, p. 4^4)- — The results of experiments on the in- 

 fluence of colophony on the biological transformation of nitrates are taken to 

 indicate that pine resin in soils produces a source of energj' for nitrate-reducing 

 soil bacteria. This is thought to explain in part why soils containing resin 

 contain less nitrate than soils containing no resin. It is further considered 

 possible that nitrification in soils is hindered by the presence of resin con- 

 stituents dissolved by all^ali salts. 



In experiments on the influence of tannin on the biological transformation 

 of soil nitrates, it was found that tannin is readily assimilated by mold fungi. 

 The results are taken to indicate that the increased growth of fungi gives rise 

 to a temporary loss of nitrogen present as nitrate and ammonia, thus explaining 

 why soils containing tannin contain only small amounts of nitrate. With refer- 

 ence to the production from tannin of poisonous substances inhibiting nitrifica- 

 tion it was found that no oxalic acid was produced from tannin by Aspergillus 

 niger. 



The addition of tannin to soils resulted in the production of a dark color not 

 due to iron, and increased the power of retaining water. Large additions of 

 tannin caused the soil to become hard, this being attributed tentatively to the 

 precipitation of colloids. 



Influence of moisture on the nitrogen changes in soils, A. E. Teaaen 

 (CentU. Bakt. [etc.], 2. Abt., 45 (1916), No. 1-5, pp. 119-135; abs. in Chem. 

 Abs., 10 (1916), No. 16, p. 2118). — Experiments on nitriflcation, denitrification, 

 and nitrogen fixation showed that nitrogen fixation especially was most active 

 when the soil contained medium amounts of moisture. 



On the nature of ammonification and nitrification, K. Miyake (Soil Sci., 

 2 (1916), No. 5, pp. 481-492, fig. 1). — A mathematical analysis, made at the 

 Tohoku Imperial University, Japan, of the processes of ammonification and 

 nitrification in soils as described in experimental work by others is reported. 

 On the basis that the processes of ammonification and nitrification are auto- 

 catalytic chemical reactions, it is pointed out that in these processes the maxi- 

 mum increase of ammonia and nitric acid in a unit of time occurs when the 

 total amount of production due to these processes is half completed. 



" Increases of ammonia and nitric acid in the processes are in accordance 



X 



with the formula: Log =K (t — ti), where x is the amount of am- 



A — X 



monia and nitric acid which has been produced at time t, A is the total amount 



of ammonia and nitric acid produced during the process, K is a constant and <, 



is the time at which half of the total amount of ammonia and nitric acid is 



produced." 



