618 EXPERIMENT STATION EECOED. 



not to the presence of the leguminous plants. The lower nitrogen content of 

 leguminous plants in the mixtures is attributed to their smaller growth. The 

 fertilizers applied had more effect on the nitrogen content of the cereals than 

 on that of the leguminous plants. The nitrogen production per unit area was 

 greater with the mixtures than the sum of nitrogen production by the separate 

 crops, but was influenced to a greater extent by fertilizers in case of separate 

 crops than in mixtures. 



The formation of calcium, carbonate in the soil by bacteria, C. T. Giming- 

 jiAM {Jour. Agr. Sci., // (1911), No. 2, pp. I'f5-l/i9). — Continuing investigations 

 by Hall and Miller (E. S. R, 17, p. 1048) which indicated that calcium salts 

 of organic acids such as oxalic are oxidized to carbonate by the action of molds 

 and bacteria, the author confirmed this conclusion and succeeded in isolating 

 from Rothamsted and Wye soils 6 types of bacteria which were capable of 

 converting calcium oxalate into carbonate. The rate of conversion varied with 

 the different types and with different conditions of culture. The best results 

 were obtained with a clear soil extract. The possibility of enzymic action was 

 removed by ti-eating the culture solutions with toluene or chloroform which 

 completely prevented carbonate formation. The formation of carbonate was 

 more rapid with mixed than with pure cultures, but it was impossible to secure 

 any action with either under anaerobic conditions. The 6 types of bacteria 

 isolated are not described. 



Changes in the so-called physical properties of soils by freezing, heating, 

 and the addition of salts, W. Czermak (Landw. Vers, ^tat., 16 {1912), No. 

 1-2, pp. 75-116). — The author studied the hygroscopicity as determined by a 

 modification of the Rodewald-Mitscherlich method (E. S. R., 15, p. 847) and the 

 soluble nitrogen of (1) soils which had been alternately frozen and thawed, 

 (2) soils which had been subjected for 2 hours in succession to steam under 

 a pressure of from 1.5 to 2.5 atmospheres, and (3) soils to which calcium 

 chlorid and aluminum sulphate had been added. Pot experiments were also 

 made with soils so treated, as well as with those to which electrolytes — calcium 

 and thorium chlorids — had been added ; those fertilized with monopotassium 

 phosphate and potassium and anunonium nitrates; and those treated with a 

 0.025 ampere current of electricity for 24 hours. 



The modification of the Rodewald-Mitschelich method consisted in reversing 

 the usual order of procedure, namely, starting with soils with their natural 

 water content, bringing them to moisture equilibrium in a vacuum desiccator 

 over 5, 7.5, and 10 per cent sulphuric acid, and finally determining the moisture 

 content by drying over phosphorus pentoxid. 



Freezing, heating, and the addition of electrolytes reduced the soil surface 

 and consequently the hygroscopicity by coagulating the soil colloids. Coagu- 

 lation of the soil colloids was increased by alternate freezing and thawing and 

 by the length but not by the intensity of the freezing. Soil colloids, coagulated 

 by freezing, absorbed a part of the nitrogen in the soil solution and thus re- 

 duced the amount readily available. Heating with steam under pressure fre- 

 quently increased the solubility of the nitrogen as a result of purely chemical 

 changes. The addition of calcium chlorid and aluminum sulphate reduced the 

 hygroscopicity cf soils, the reduction being more pronounced in the case of the 

 former. 



The results with pot experiments were inconclusive, the electrolytes — calcium 

 and thorium chlorids — added proving toxic to the oat plants used in the experi- 

 ments. The author concludes that pot experiments are not suited to the study 

 of physical changes in soils. 



