1910] SOILS — FERTILIZERS. 121 



dealing with chemical analyses of water extracts of several cropped and un- 

 cropped soils as a measure of their relative productivity, have been previously 

 noted (E. S. R., 38, pp. 812, 813). These studies also included analyses of the 

 soils by the so-called complete, or fusion, method, and by the hydrochloric- 

 acid and citric-acid extraction methods, the results of which are here reported 

 for purposes of comparison. The conclusions reached may be summarized as 

 follows : 



Low figures for the important plant food elements (including potash, calcium 

 oxid, magnesium oxid, phosphoric acid, and nitrogen), by water extraction and 

 to a lesser extent by citric-acid extraction, were found to be in general accord 

 with the crop-producing power of the soil. Except in the case of highly 

 silicious soils, the complete analysis and hydrochloric-acid extraction methods 

 are held to be worthless as criteria of the present productivity or probable 

 endurance of the soil. Individual soils of a given series and class (Yolo silty 

 clay loams) showed less variation in chemical composition than did repre- 

 sentatives of different series of another physical class (fine sandy loams). The 

 wide variation in crop yields and in the figures for water extractions within 

 a given series and soil type are held to indicate that physical classification into 

 types is inadequate as a means of predicting probable yields or determining 

 fertilizer requirements. 



The relative " rawness " of some humid subsoils, P. M. Harmer (Soil Sci., 

 5 (1918), No. 5, pp. 398-J t 03, figs. 2). — The author describes vegetative experi- 

 ments made in the greenhouse at the Minnesota Experiment Station with both 

 surface soils and subsoils taken from three prairie fields and four forested 

 areas in the State in a st\idy of the relative "rawness" of the subsoils of 

 humid regions. The soils are said never to have been plowed. The prairie 

 subsoils were found to be quite calcareous. 



Experiments were made in 1915-16, employing only one soil sample from 

 each region, the surface 12 in. of the prairie soil and 6 in. of the forested area 

 being used, together with the corresponding subsoil from the third and fifth 

 foot levels. The soils were placed in wooden boxes 12 in. square and S in. deep 

 and cropped to both barley and alfalfa, the latter being well inoculated. The 

 barley made a normal growth on the surface soil, producing well-filled heads, 

 while that grown on the subsoil was stunted, yellowish-green in color, and 

 produced very little seed. Three crops of alfalfa were obtained and indicated 

 that the subsoils were as unproductive of alfalfa as of barley. 



In the fall of 1916 more extensive experiments were begun with the seven 

 different soils, the surface 6 in. and the corresponding subsoil from the third 

 foot level being employed. These soils were placed in galvanized-iron pots and 

 cropped with well-inoculated alfalfa plants transferred from a field sown five 

 months before. Two subsoils, both low in carbonates and from forested areas, 

 yielded as well as both the corresponding and other surface soils, while the 

 remaining subsoils produced only from one-sixth to one-half as much as the 

 corresponding surface soils. The nitrogen content ,of the productive subsoils 

 did not exceed that of the unproductive subsoils. 



It is concluded, therefore, that " in the humid State of Minnesota some of the 

 glacial subsoils are as productive of alfalfa as surface soils when inoculation 

 is assured, but others are quite unproductive, and the rawness is not associated 

 with *n especially low nitrogen content or with a lack of carbonates." 



See also a previous note (E. S. R., 39. p. 620). 



The influence of plant residues on nitrogen fixation and on losses of nitrate 

 in the soil, H. B. Hutchinson (Jour. Agr. Sci. [England], 9 (1918), No. 1, pp. 

 92-111, figs. 3). — The author describes field, laboratory, and pot experiments 



107338°— 19 3 



