82 SOIL SCIENCE [BoT. Absts., Vol. IX, 



tankage but did not equal dried blood. In pot cultures bat guano gave better results than 

 dried blood, tankage, or ammonium sulphate, and in field tests with oats it also proved su- 

 perior to ammonium sulphate. Because of its relatively high nitrogen content and because 

 of its light weight when dry it is recommended primarily for mixture with other fertilizers. — 

 L. J. Stadler. 



534. Bagtjlet, A. Building up the fertility of the soil. Jour. Dept. Agric. Union of South 

 Africa 1 : 755-759. 1920. — A general discussion of improving soil fertility by means of humus, 

 lime, and fertilizers. — J. J. Skinner. 



535. BouYotrcos, George B. A new classification of soil moisture. Soil Sci. 11: 33—47. 

 1921. — On the basis of freezing point determination of soil of various types and water contents 

 and determinations of the per cent of water which freezes in soils at different temperatures 

 as determined by the use of the dilatometer, the soil water is classified as gravitational, free 

 (water which freezes for the first time at a supercooling of — 1.5°C.), capillary adsorbed 

 (water which freezes at the supercooling of — 4°C.), and combined water, which does not freeze 

 even at — 78°C. The capillary-adsorbed and combined water are called unfree. — W. J. Rob- 

 bins. 



536. Botjyoucos, George B. The concentration of the soil solution around the soil par- 

 ticles. Soil Sci. 11: 131-138. 1921. — The concentration of the soil solution in intimate con- 

 tact with the surface of the soil particles is less than that of the mass of the soil solution. 

 This is indicated (1) by the diminution of the freezing-point lowerings of soils by successive 

 freezing and thawing; (2) by the liberation of unfree water from soils, by successive freezing 

 and thawing; (3) by the abnormally greater increase in the freezing-point depression of soils 

 as the moisture content decreases; and (4) the equality in the freezing-point lowering between 

 the supernatant liquid and the soil which bathes it. — W. J. Robbins. 



537. Davis, R. O. E. Atmospheric nitrogen for fertilizer. U. S. Dept. Agric. Yearbook 

 1919: 115-123. 1920. — The sources of natural nitrogen fertilizer supply are shown to be in- 

 adequate to meet the increased future demands. The desirability of a method of utilizing 

 the atmospheric nitrogen was emphasized. A discussion of the practicality of 5 principal 

 methods for conversion of atmospheric nitrogen into available fertilizer compounds showed 

 that the Haber and the cyanamid processes were the only ones adapted to use in the 

 U. S. A. at present. — C. J. Shirk. 



538. EsPE, Knute, and Lawrence E. Lindley. Soil survey of Hamilton County, Iowa. 

 Advance Sheets Field Operations Bur. Soils, U. S. Dept. Agric. 1917: 5-30. Fig. 1 and map 

 {colored). 1920. — Hamilton County is situated in the north central part of Iowa in a prairie 

 region. The prevailing flat topography is intercepted by the precipitous slopes of Boone 

 River and by morainic ridges. The general elevation is between 1,100 and 1,200 feet above 

 sea level. — Drainage within the county as a whole is imperfect. — The mean annual precipita- 

 tion is 34.55 inches. The normal growing season is 14G days. — Agriculture, which is the princi- 

 pal industry in Hamilton County, consists mainly in the production of corn, small grain, and 

 hay combined with the raising and feeding of hogs and other live stock. Corn is the main 

 crop. — The soils of the county are glacial in origin, in appearance they are predominantly 

 dark. Large poorly drained areas occur. In great part the soils of the county are calcareous, 

 alluvial soils are inextensive. Eroded strips bordering the stream valleys are characterized 

 by light brown to gray surface soils. Such areas are for the most part forested and originally 

 were all forested. Peat and muck occur in shallow and basin-like areas representing former 

 ponds or lakes. Small areas of alkaline soils occur in the swales, ponds, or sloughs that have 

 recently been drained. Corn is most susceptible to injury from the alkali. Drainage is the 

 chief factor in correcting the alkaline condition. — Improved land constitutes 90-95 per cent 

 of the County. The average size of farms is about 179 acres. — F. B. Howe. 



539. Geib, W. J., Clarence Lounsbury, and Martin O. Tosterud. Soil survey of 

 Waupaca County, Wisconsin. Advance Sheets Field Operations Bur. Soils, U. S. Dept. Agric. 



