516 EXPERIMENT STATION RECORD. 



tlie reduction of the nitrates present. It was concluded, therefore, that the 

 nitrogen required by the crop was obtained from the ammonia and nitrogenous 

 organic compounds produced by the anaerobic decomposition of the proteids of 

 the green manure. Since certain substances so produced are toxic to the crop 

 the application of green manure to poorly drained areas must be undertaken 

 with caution. 



Investigations of the gases evolved from the surface of rice soils led to the 

 conclusion that the surface film of algae, etc., which covers the surface of rice 

 soils evolves a large amount of oxygen which is dissolved by the irrigation 

 water, thus producing a highly aerated solution from which the roots in the 

 soil derive their oxygen. " In undrained soils, this solution does not penetrate 

 into the soil, and, consequently, the roots are congested near the surface of the 

 soil and the amount of soil from which they derive their food is therefore 

 limited and the crop suffers. In drained soils this strongly aerated water 

 penetrates the soil and the roots are able to penetrate to a greater depth. 

 The mass of soil from which the food supply is drawn is increased and the 

 crop benefits in proportion." Too rapid drainage, however, decreases the for- 

 mation of the surface film so that there is for all swamp paddy soils a com- 

 paratively slow optimum rate of drainage. Aeration by atmospheric oxygen is 

 less effective than that by drainage water In promoting root aeration. The use 

 of green manures in drained paddy soils induces a greater activity of the sur- 

 face film, thus improving root aeration. 



The organic constituents of soils (Rev. G^n. Agron., n. ser., 8 {1913), Nos. 3, 

 pp. 97-103; 4, pp. IJfS-lSJf). — ^This is an appreciative review of investigations by 

 the Bureau of Soils of this Department. 



Soil studies by the aid of their water solutions, R. Ballenegger (Foldtani 

 Kozlony, 43 (1913), No. 7-9, pp. 359-366). — Chemical studies are reported of the 

 water solutions of a collection of typical Hungarian soils which were prepared 

 by methods adopted by the Bureau of Soils of this Department (E. S. R., 17, 

 p. 831). The soils studied were the gray and brown forest soils, the black 

 clay, black, deep brown and alkaline plain soils, and the aluvial and sandy soils. 

 Water solutions are said to be particularly adapted for the determination of the 

 electrical conductivity. 



Ultramicroscopy of soil extracts, S. M. Muravlianskii {Poclwoviedicme 

 (Pedologie) , 15 {1913), No. 2-3, pp. 23-27). — Ultramicroscopic investigations of 

 water and ammonia-alkaline extracts of chernozem soils having a variable 

 humus content showed these extracts to be pseudo solutions. In both extracts 

 the cone was more evident, and more submicrons and particles with diffraction 

 rings appeared, the greater the humus content. The alkaline extracts showed 

 a more pronounced cone and a greater number of submicrons than the water 

 extract, while analytical data indicated that mineral constituents are prevalent 

 in the water extracts and organic constituents in the alkaline extracts. It is 

 therefore concluded that the soil colloids generally belong to organic matter. 



Microflora of the Roman experimental field, R. Perotti {Staz. Sper. Agr, 

 Ital., 46 {1913), No. 10, pp. 661-668). — The author discusses the microflora in 

 the soils of this field relative to systems of cultivation, particularly noting the 

 effect of the meteorological elements on their presence and activity and the 

 importance of modifying systems of cultivation accordingly. It was found that 

 the beneficial microbiological functions of this soil are retarded during the hot, 

 dry summer months, while the maximum beneficial activity was found during 

 the winter months, when there was more rainfall and the soil water content 

 was higher. 



A study of the formation of nitrates in various types of Virginia soil, 

 E. B. Feed {Centhl. Bakt. [etc.l, 2. Aht., 39 {1913), No. 18-19, pp. 455-468).— 



