1040 EXPERIMENT STATION RECORD. 



by simply adding lime, which gradually sets the soil potash free. If 

 the soil is poor in potash the potassic fertilizer should be used in con- 

 nection with a relatively small amount of lime, or of slag if phosphoric 

 acid is also deficient. 



On the question of the decomposition of nitrates by bacteria, 

 S. A. Sewerin (Centbl. Bald, u. Par., 2. AM., 3 (1897), Ros. 19-20, pp. 

 504-517; 21-22, pp. 554-563, figs. 3). — An account is given of culture 

 experiments with 29 different organisms isolated from horse manure 

 in previous investigations of the author on denitrincatiou. 1 Of these 

 29 cultures 3 were strictly anaerobic, 1 was a facultative amerobe, 

 and 25 strictly rerobic. The culture medium used was meat peptone 

 bouillon containing 0.3 per cent sodium nitrate. Cultures were made 

 in Pasteur tubes containing 20 cc. of the bouillon which were kept at 

 30° C. temperature for ten days in a thermostat. At the end of that 

 time the different cultures were tested for the presence of nitrates 

 and nitrites. In 2 cases no reaction was obtained for either nitrites 

 or nitrates, showing that denitrification was complete. In 9 cases 

 no nitrates were found, but nitrites were abundant. In 18 cases the 

 nitrates were apparently unaltered. In further experiments with the 

 9 cultures which formed nitrites it was found that when the propor- 

 tion of nitrate in the culture medium was reduced to 0.1 per cent, 2 of 

 the cultures destroyed all traces of both nitrates and nitrites in ten 

 days; the remaining 7 transformed the nitrates into nitrites, but did 

 not reduce the nitrites in that time. Of these 7 organisms 4 were 

 inicrobacteria, 1 was a rod-shaped bacterium, 1 a coccus, and 1 Bacillus 

 indicus. The different organisms are described in detail and experi- 

 ments in different culture media under different conditions are reported, 

 especial attention being given to a comparison of the reducing power 

 for nitrates of the author's culture No. 3 and Bacillus pyocyaneus. 

 The latter experiments showed that both organisms rapidly reduce 

 nitrates, a part of the nitrogen apparently being used to form organic 

 compounds. With moderate surface aeration a very small amount of 

 the nitrogen was converted into ammonia. By far the greater part of 

 the nitrate, however, was evidently reduced to free nitrogen or oxids 

 of nitrogen. The reduction of nitrates was delayed in each case by 

 the admission of air and by the formation of nitrites and alkali by the 

 activity of the organism. It appears from these experiments that 

 these organisms may be injurious in the soil in destroying nitrates. 

 The precaution to be taken against their harmful activity is thorough 

 aeration of the soil by proper cultivation. 



The evaporation of water from water surfaces, from the soil, and by vegeta- 

 tion, E. Canestkim (AM Sue. Veneto-Trentina Sci. Nat., 2. ser., Ill, No. 2). 



Soil classification especially as applied to Russia, N. Ssibikzeff (Ann. a vol. 

 et Mineral. Russia, .' (1S97), No. 5,p}). 73-78). 



' Centbl. Bakt. u. Par., 2. Abt., 1 (1895), pp. 97, 160. 



