SOILS — FERTILIZERS. 21 



acterizing Europeau Russia according to drought periods during tlie growing 

 season, April to October, inclusive. 



A dry period is defined as one during which not more than 5 mm. of precipi- 

 tation falls. The probability of such periods is computed in percentages 

 denoting the ratio of the number of years with the given dry periods to the 

 total number of years during which the obserA-ations were made, viz, sixteen, 



Data from 390 meteorological stations were utilized in the preparation of 

 the maps. The maps show, in general, that the rainfall gradually increases 

 from April to June then diminishes to the end of the growing period. 



SOILS— FERTILIZERS. 



Soils of the cut and burned over areas of north Idaho, J. S. Jones and 

 C. W. CoLVEB {Idaho Sta. Bui. 81 {1915), pp. 20, figs. 5). — This survey deals 

 with the general characteristics, physical and chemical properties, crop 

 adaptations, and fertility requirements of the soils of the cut and burned over 

 areas of the panhandle of Idaho, which are included mainly in Bonner, 

 Kootenai, and Latah counties and to a less extent in Clearwater and Shoshone 

 counties. 



The soils vary from river and lake bottoms to bench lands and level open 

 prairies. The red sandy and silt loams are the predominating soil types. It is 

 stated that the lowlands are rich in plant food, but that they need drainage. 

 The bench and other highlands are rich in mineral plant food, but are usually 

 acid in reaction and deficient in nitrogen and active organic matter. The 

 open prairies, while not deficient in nitrogen, are usually acid and need treat- 

 ment to make the native supply more readily available. " Unquestionably in 

 the management of the cut and burned over lands the key to immediate and 

 permanent success is a thorough understanding of practicable means of 

 getting the element nitrogen into them and of making it available as plant 

 food." 



Data showing the amount of the various soil constituents are appended. 



Bond County soils, C. G. Hopkins et al. {Illinois 8ta. Soil Rpt. 8 {1913), 

 pp. 58, pi. 1, figs. 9). — This is the eighth of the series of the Illinois County soil 

 reports and deals briefly with the physiography, topography, and formation of 

 the soils and more fully with soil material and soil types, chemical composition 

 of the soil, and field tests of the fertilizer requirements of some of the prevail- 

 ing types. 



Bond County lies in the lower Illinois glaciatiou. The soils of the county are 

 divided into four classes, as follows: (1) Upland prairie soils, (2) upland tim- 

 ber soils, including those zones along stream courses over which forests once 

 extended, (3) ridge soils, including those on moraiual ridges most of which have 

 been forested, and (4) bottom-land soils, including the flood plains along 

 streams. The timber lauds are divided into level, undulating, and hilly areas. 

 The ridge soils are divided into pervious and almost impervious tyi^es. 



The gray silt loam on tight clay of the upland prairie soil occupies nearly 33 

 per cent of the area of the county, while the brown-gray silt loam on tight clay, 

 the yellow silt loam, and the yellow-gray silt loam are in their order next in 

 extent, covering about 16.5, 16, and 13 per cent of the area respectively. 



The total quantities of some of the necessary elements of fertility " are ex- 

 tremely limited when measured by the needs of large crop yields. . . . The 

 variation among the different types of soil in Bond County with respect to their 

 content of important plant-food elements is also very marked. Thus the richest 

 prairie land (black silt loam on clay) contains about twice as much phosphorus 

 and nitrogen as the common upland timber soils, and the bottom lands are still 



