SOILS FERTILIZERS. 817 



lower parts of the curve where the dye solutions are weak vary considerably, 

 but from 0.0375 per cent to 0.1125 per cent they are constant. ... In actual 

 experimental work, then, the equilibrium solution chosen should be one between 

 0.0375 and 0.1125 per cent ; the most convenient is 0.05 per cent." 



Study of the physical analysis of the fine particles of clay, A. Muntz and 

 H. Gaudkchon {Ann. Inst. \iit. Acjron., 2. scr., 12 {JUIS), Xo. 2, pp. 233-271, 

 figs. 5). — This is a more detailed account of investigation's briefly reported 

 elsewhere (E. S. R.. 30, p. 422). 



Soil investigations, J. W. Ames and E. W. Gaitheb (Ohio Sta. Bui. 261 

 {1913), pp. Ji-'ti>-512). — Investigations on the composition of 126 calcareous and 

 noncalcareous soils of Ohio are reported, special attention being directed to the 

 phosphorus content as regards deficiency, availability, and combination. 



The gradual loss of calcium carbonate from cultivated soil was illustrated by 

 soils, originally of limestone formation but containing no calcium carbonate, 

 in which the total calcium and magnesium and that soluble in fifth-normal 

 nitric acid was greater than in soils overlying sandstone and shales. An acid 

 soil receiving 12.000 lbs. of ground limestone in 1907 contained only 2.100 lbs. 

 of calcium carbonate at the end of a 5-year rotation in 1912. 



Sands, silts, and clays examined exhibited no marked differences in chemi- 

 cal composition, although the clays and clay loams generally contained less 

 total silica and slightly more iron, alumina, and potassium. Calcareous soils 

 contained less silica and more phosphorus and potassium than noncalcareous 

 soils. Black clay loams of limestone origin contained more pho.sphorus and 

 nitrogen than other soils analyzed. In most cases they contained calcium car- 

 bonate. The surface soil to a depth of G in. contained more phosphorus than 

 the subsoils (G to 3G in.) except in a few cases where the latter contained 

 considerable calcium carbonate, and also more nitrogen and organic matter 

 and fine particles. The total silica was generally largest in the surface soil 

 while the silica soluble in fifth-normal nitric acid was usually greater in the 

 subsoil. The total iron, alumina, and potassium were greater in the subsoil 

 than in the surface soil. Soils containing no calcium carbonate contained more 

 calcium and less magnesium in the surface than in the subsoil. Soils contain- 

 ing calcium carbonate contained more of both calcium and magnesium in the 

 subsoil than in the surface soil, the calcium being in excess of the magnesium. 

 Noncalcareous soils always contained more magnesium than calcium in the sub- 

 soil and generally more in the soil as a whole. All the soils examined con- 

 tained more calcium than magnesium soluble in fifth-normal nitric acid. 



The litmus paper test proved satisfactorj'- as a qualitative test for the pres- 

 ence or absence of natural calcium carbonate in soils. " Of 12G surface soils 

 examined for calcium carbonate and reaction, only five of those containing 

 calcium carbonate reddened blue litmus paper. All the soils which gave an 

 alkaline reaction with red litmus contained calcium carbonate. . . . 



"The total phosphorus content of the soils studied varied from 0.3 per cent, or 

 G,000 lbs., per acre to 0.025 per cent, or 500 lbs., of phosphorus per acre in G in. 

 of soil." Fourteen showed the presence of more than 0.1 per cent of total phos- 

 phorus. Soils containing calcium carbonate showed a larger supply of total 

 phosphorus than the noncalcareous soils. The average phosphorus content of 

 calcareous surface soils was 1,310 lbs. per acre, compared with 013 lbs. and 986 

 lbs. for the noncalcareous soils from the eastern and western sections of the 

 State. 



Black clay loams of limestone origin contained the most total phosphorus 

 followed in order by the calcareous clays and clay loams. Alkaline soils con- 

 taining natural calcium carbonate contained more available phosphorus (solu- 

 ble in fifth-normal nitric acid) than acid soils. Calcareous sands and sandy 



