5G() EXPERIMENT STATION RECORD. 



inttTvals of a week to 10 dayw. It was found that Htirrin^r and ])nlveri/.in},' the f^oil 

 stimulated tlie development of soil bacteria. The niiiidK-r ])er gram of dry soil 

 inerease.1 from 2,000,000 to 12,600,000 in 24 days. 



The (-ffeet of mineral fertilizers on the development of Sdil ))act(Tiu was investi- 

 gated, the experiments being conducted in galvanized-iron pots. The soil samples 

 were i)laced in the pots and a complete fertilizer composed of sodium nitrate, 

 potassium chlorid, and sodium phosphate was added to each. Bacterial analyses of 

 the soil in the pots were made at intervals and the results showed that even the 

 liberal use of mineral salts, which actas great stinuilators toi)laiit gniwth, were with- 

 out appreciable effect on the bacterial development. 



A study was made of the predominating bacteria in a soil sample, which was exam- 

 ined by methods of dilution and culture. It was found that 3 species of bacteria 

 predominated. The first, which is designated as "Bacterium A" and to which the 

 author has given the name Streptothrix soli n. sp.,was represented by 1,600,000 per 

 gm. of dry soil; the i^eeond. Bacterium Jiocosum n. sp., 1,200,000; and Bacillus deJarari- 

 ensis, 300,000. These different organisms are described in considerable detail and 

 their relationship pointed out. 



Stuflies are rej)orted on the nitrogen-assimilating l)acteria of soils, the author 

 reviewing the investigations of Berthelot, Winogradsky, Beijerinck, and others. A 

 preliminary report is given of his own studies of oligonitrophilous bacteria, which 

 were isolated from Delaware soil. Three organisms, designated as Azotobacter I, 

 Pseudomonas I, and Bacillus I, were studied. At the end of 28 days the first species 

 had shown no gain of nitrogen in its culture, seeming to indicate that this organism 

 when growing alone in pure cultures in nitrogen-free media is without the power of 

 utilizing free atmospheric nitrogen. The other 2 organisms showed a decided 

 increase in the amount of nitrogen, the gain in the case of the Pseudomonas species 

 being 4.3 times the original content, while for the Bacillus the gain was 3.4 times the 

 original content. The characters of these organisms are briefly described. 



The activity of bacteria in soils, F. Muth ( Verhandl. Naturw. Ver. Karlsruhe, 16 

 {1902-3), pp. 69-124, figs. '-0). — A summary of information on this subject. 



FERTILIZERS. 



Cover crops as green manure, C. L. Penny {Delaware St((. Bid. 60, pp. 44, figs. 

 2.) — This is a discussion of this subject based on yields and analyses of crops grown 

 on the station plats in a series of experiments begun 2 years ago in cooperation with 

 this Department. In connection with the report of the results of this investigation 

 the author summarizes "the generally accepted views of the present day on plant 

 nutrition in so far as it relates to the use of cover crops." incorporating much of the 

 data which have been reported in previous bulletins of the station. 



The tabular data reported include the weights per acre of the portion above ground 

 of each crop in the state in which it was harvested, with the percentage content of 

 nitrogen, potash, and phosphoric acid, and the weight per acre of each of these con- 

 stituents; the air-dry weight per acre of the roots of several crojis, in some cases in 2 

 layers, tlie first 8 in. and the next 4 in., with the percentage composition; the weight 

 per acre and the percentage of the portion above ground and of the roots separately, 

 both on the air-dry basis, and the weight per acre of the 3 chief constituents; 

 for comparison a money valuation of each crop, the nitrogen being rated at 12 cts. a 

 pound, the potash at 5 cts., and the phosphoric acid at 3 cts.; the relative yield of 

 dry matter, nitrogen, potash, and pliosphoric acid found in the tops and the roots, 

 stated as a percentage of these respective constituents found in the whole crop; the 

 moisture content of the surface soils used to grow the cover crops, both plowed and 

 unplowed; and the moisture content of the corresi)onding subsoils. 



The 8 crops giving the highest money valuation for the nitrogen, potash, and 

 phosphoric acid produced per acre were as follows; Rye and vetch S!25.84, rape 

 124.99, crimson clover |22.37, cow horn turnips $21.01, soy beans $20.44, rye and 



