14 EXPERIMENT STATION RECORD. 



time, in order that the observed soil and plant data might be as definitely related as 

 possible. The plants were cnt up when fresh, care being taken to avoid wilting, 

 into fine pieces, to permit of reliable sampling. Then 100 gin. were dried for moist- 

 ure determination, and 20 gm. were transferred at once to the mortar and thoroughly 

 ciushed with the pestle, after which 500 cc. of distilled water were added. The 

 whole was stirred with the pestle during 3 minutes, and the solutions were decolor- 

 ized and filtered." Decolorization was accomplished by the use of 3 to 5 gm. of 

 carbon black to 100 gm. of soil, or to 20 gm. of green plant. This usually rendered 

 the solution colorless after standing 15 to 20 minutes with frequent agitation. 



The methods used in analyzing the extracts have been described in a previous bul- 

 letin of the Bureau (E. S. R., 15, p. 457). The earlier studies reported were made 

 with fresh samples of soil. For reasons already noted (E. S. R., 15, p. 233) oven-dried 

 samples were used in the later work. 



The results show in general that relatively large amounts of salts are either actually 

 in solution in the soil moisture of the fields examined, or are in such form that they 

 at once enter solution when that moisture is diluted with distilled water, although 

 there were considerable differences between the groups of soils from the different 

 States in the amounts of solids which were recovered from them by extracting with 

 distilled water. It was also shown that the application of fertilizers very materially 

 increased the amounts of salts recovered from the soils. 



"The largest amount of solids recovered from the surface-foot of any soil was 034.7 

 parts per million in the case of a Janesville loam, and the smallest amount, omitting 

 three doubtful results, came from the Selma heavy silt loam, 140.9 parts per million 

 of the dry soil. The first, or largest amount, represents well up toward 2 tons of 

 soluble matter per acre-foot, or 0.3 per cent of the soil moisture, computed on a sat- 

 uration equal to one-third the dry weight of the soil. . . . There appears to be 

 no relation of amounts of water-soluble salts to the size of soil grains, unless possibly 

 the phosphates recovered do increase as the size of the soil grains decreases." The 

 total water-soluble salts recovered from 8 soil types ranged from nearly an even ton 

 per acre in Norfolk sand to 3 tons in Janesville loam, distributed through the surface 

 4 ft. of soil. 



Data are also reported showing the increased amounts of soluble matter obtained 

 from soils by repeated washing and drying and by continuous percolation; the 

 amounts of soluble salts carried by well and drainage waters, and plant food removed 

 from soils by crops as compared with the amounts recovered by distilled water. The 

 ground waters were found to have a higher content of nitric acid than running waters. 

 It was also shown "that, from the surface 4 ft. of soil, there was recovered per acre 

 enough nitrogen, by the three-minute washing, for a crop of 2.] tons of clover hay. 

 Of potash, there was enough recovered for two, and of phosphorus enough for 

 about five such crops." 



77. — Relation of crop yields to the amounts of water-soluble plant-food material* recov- 

 ered from soils (pp. 7M-124, pi. 1, figs. (i). — This paper presents "a study of existing 

 field conditions and relations, [including] a critical comparative study of 8 soil types, 

 bearing the same 2 crops, where all of the conditions under control were made as 

 closely similar as practicable. . . . The prime object was the fullest attainable 

 knowledge of the character of the soil solution and a correlation of this character 

 with different soil types, with different methods of soil management, and with the 

 yields of crops. In carrying out that study the work was so planned that, as far as 

 possible, the soluble-salt determinations were made in connection with some crop 

 whose yields were ascertained and whose growth was under observation." Previous 

 work of like nature, especially that done at Rothamsted and at the Wisconsin Sta- 

 tion, is reviewed. 



