420 EXPERIMENT STATION RECORD. [Vol.41 



Pyrolusite from Virginia, T. L. Watson and E. T. Wherry {Jour. Wash. 

 Acad. ScL, 8 (1918), No. 16, pp. 550-560, fig. i).— This is a report of a study of 

 the geology and mineralogy of manganese oxid crystals and crystalline miner- 

 als from the Virginia locality. 



The comparative rate of formiation of soluble material in cropped and 

 virgin soils as measured by the freezing-point method, C. E. Millar {Soil 

 SH., 7 {1919), Xo. Jf, pp. 253-257, figs. 2).— Tests conducted at the Michigan 

 Experiment Station are reported in which 6 different soils in cropped and 

 virgin condition were washed with distilled water until the concentration of 

 the soil solution was reduced to only a few parts per million, and the effect of 

 such treatment measured on the subsequent rate of formation of soluble ma- 

 terial as determined by the freezing-point method. Soils 1 and 2 were silt 

 loams relatively deficient in organic matter, 3 and 4 were lowland soils con- 

 taining considerable organic matter, 5 was a sand soil, and 6 a very fine sandy 

 loam. 



It was found that the tendency for the concentration of the soil solution to 

 reach a maximum and decrease before the end of the 40-day period was prac- 

 tically overcome by the washing. Some tendency for the concentration to de- 

 crease was exhibited by the virgin sample of soil 1 and by both the cropped 

 and virgin samples of soil 4. The changes, however, were not suflficient to 

 affect the conclusions. Nos. 1, 2, and 5 showed a decidedly greater rate of for- 

 mation of soluble material in the virgin than in the cropped samples. In ad- 

 dition, the total concentration of the soil solution was much higher in the 

 case of the virgin samples. 



Of the remaining soils, Nos. 3 and 4 showed very little difference in either 

 the rate of formation of soluble material or the total concentration of soil solu- 

 tion attained. These two soils showed very little change in productivity as a 

 result of several years' cultivation. Soil 6 showed only a slightly greater rate 

 of formation of soluble material in the virgin than in the cropped sample, the 

 final concentration of soil solution being virtually the same. 



The author feels justified in suggesting that " a marked deci*ease in the rate 

 of formation of soluble material is one of the changes a soil may undergo as a 

 result of several years of cultivation with the return of little fertilizing ma- 

 terial." 



Changes in composition of the soil and of the water extract of the soil, 

 following addition of manure, P. L. Hibbard {Soil Sci.. 7 {1919), No. 4, pp. 

 259-272, figs. 3). — In experiments at the University of California, fresh manure 

 was mixed with silty clay loam and sandy loam soils at rates of 1, 2, and 5 per 

 cent and the mixtures kept in loosely covered glass jars under optimum mois- 

 ture conditions. ■ 



Periodic analyses showed that the carbon dioxid content of the soil atmos- 

 phere was increased in proportion to the amounts of manure added, while the 

 total carbon content gradually decreased, such decrease being more rapid for 

 the larger amounts of manure. The total nitrogen content remained constant. 



The total water-soluble matter decreased within a few weeks in the 1 per 

 cent mixture to below that of the control soil, after which it gradually increased 

 to considerably more than that in the control soil, but never to an amount equal 

 to the sum of that in the control soil and that in the added manure. The 2 and 

 5 per cent manure mixtures showed relatively greater decreases and increases. 



The changes were not relatively the same for the different ions and complexes. 

 In the soil extract there was less change in calcium and magnesium than in 

 potassium, sulphates, and nitrates. The nitrates at first quickly disappeared 

 and later increased considerably over the amounts in the control. These changes 

 are attributed to biochemical action. 



