VVATKK SOILS. \)57 



humus of which nitrogen is one of the component parts. When grains are grown in 

 a rotation with clover, and Earm manures are applied to the corn crop, the losses of 

 nitrogen and humus are reduced toa minimum and the crop-producing power of the 

 soil is increased." 



The second investigation reported in this bulletin has already been briefly noted 

 in the Record I E. S. !.'., in, p. 28). It was designed to show by means of cultures 

 in sterile sand the extent to « hich plants can utilize the mineral food dissolved in the 

 soil water. It was found that -'when wheat, oats, ami barley weresupplied only with 

 soil ieachings they failed to make a normal growth and to produce seeds, showing 

 that water alone acting upon a fertile soil is nol sufficient to supply a crop with its 

 mineral food, but a large part is taken in other terms and that it is necessary for the 

 farmer by means of cultivation, manures, and rotation of crops to increase the reserve 

 plant food of the soil, not soluble in water, so as to secure maximum yields." 



The third investigation was a continuation of similar studies reported in previous 

 bulletins (E. S. R., 11, p. 1018). As in the previous experiments Mil. soil contained 

 in a series of boxes was mixed indifferent cases with casein, albumin, wheal gliadin, 

 and other organic compounds. "In some of the boxes known amounts of mineral 

 substances were also added. The boxes were exposed out of doors for one year to 

 allow humification to take place. Previous to exposure, samples of the soil and of 

 the various organic substances used were analyzed and after the close. if the year they 

 were again weighed and analyzed." The object of these experiments was to show 

 the extent to which the proteid compounds of feeding stuffs and manures combine 

 with the inert phosphoric acid and potash of the soil to form humates. The lo>s of 

 nitrogen during the process of humification and the form in which nitrogen exists in 

 humus were also studied. The results show that appreciable amounts of the phos- 

 phoric acid and potash of the soil entered into combination with the organic matter 

 during the process of humification and were thereby rendered more soluble. There 

 was at the same time a loss of nitrogen. Little of the nitrogen remaining in the 

 humus was in amid form, ''the larger portion being in forms allied to insoluble pro- 

 teids and not readily acted upon by a dilute acid pepsin solution. 



" In the process of humiheation, an appreciable amount of the organic matter is 

 rendered soluble and is obtained in the soil Ieachings." 



The value of humates as plant food is briefly discussed. 



A comparison of the organic matter in different soil types, F. K. Cameron- 

 {Jour. Amer. Chem. Soc, r, \ 1905), No. 3, pp. 256-258).— -The results of determina- 

 tions by a method previously noted ( I*'-. S. It., 15, p. 744) of organic matter in 1,340 

 samples of --oil and 1,220 subsoils representing 'SM soil types are summarized. 



"The average contenl of organic matter for all these samples is 2.06 per cent for 

 the soil and 0.83 per cent for the subsoil. . . . An examination of the results seems 

 to indicate that, generally speaking, the range of color of the soil within any given 

 soil type varies in the order of the content of organic matter. The color of a soil, 

 however, is by no means a safe indication of its content of organic matter. . . . The 

 variation in the total organic matter in different samples of the same soil type is fully 

 as great as between samples of different types. . . . Not only has the mineral matter 

 an important part in determining color, hut further, the organic matter in different 

 soils is of a widely different nature. . . . 



" For these n asons the Bureau of Soils proposes in the future to omit the determi- 

 nation of the total organic matter as a regular integral part of the mechanical analysis 

 of a soil, except in special cases when it is obviously of importance in defining a 

 type. ' ' 



Contribution to the knowledge of the products of weathering of silicates 

 in clay, volcanic and laterite soils, J. M. van Bemmelen [Ztichr. Anorgan. 

 Chem., /'.' i 1904), No. S, />/>■ 265S14). — The author claims that extraction of a soil 

 with hydrochloric acid by ordinary methods gives no accurate knowledge of the 



