402 NATURE AND PROPERTIES OF SOILS 

 Table LXXXVIII 



LOSS OF CARBON FROM THE SOIL IN DRAINAGE, EXPRESSED IN 

 POUNDS TO THE ACRE PER YEAR. CORNELL LYSI METERS. 



Treatment 



Carbon 

 (pounds) 



Bare soil 1391 273 



Rotation 1350 265 



Grass 1193 234 



tained in the Cornell lysimeters. The application of two tons 

 of green-manure to the acre would be necessary to replace 

 even the drainage loss cited above. 



Small amounts of carbon may be removed by means other 

 than drainage or diffusion into the atmospheric air. Nu- 

 merous investigators x have shown that plants are capable 

 of assimilating various organic materials. Recently it has 

 been demonstrated that higher plants may utilize a consid- 

 erable variety of carbohydrate compounds. 2 Such materials, 

 when thus assimilated, no doubt supply the plant with en- 

 ergy and thus are foods rather than nutrients. The ready 

 response of certain crops, such as maize, to applications of 

 farm manure lends plausibility to the theory that considerable 

 carbon may be removed from the soil by plants and that the 

 carbon dioxide of the air is not the only immediate source of 

 the element carbon. 



221. The sulfur cycle.— Sulfur is an essential plant nu- 



1 Hutchinson, H. B., and Miller, N. H. J., The Direct Assimilation of 

 Inorganic and Organic Forms of Nitrogen by Higher Plants: Centrlb. f. 

 Bakt., II, Band 30, S. 513-547, 1911. 



2 Maze, P., Influence, sur le developpement de la plante, des substances 

 minerales qui s'accumulent dans ses organes comme residus d' assimila- 

 tion; Compt. Rend. Sci., Paris, Tome 152, pp. 783-785, 1911. 



Ravin, P., Nutrition carbonee des plantes a Vaide des acides organique 

 libres et combines; Ann. Sci. Nat. Bot., Ser. 9, No. 18, pp. 289-446, 

 1913. 



Knudson, L., Influence of Certain Carbohydrates on Green Plants; 

 Cornell Agr. Exp. Sta., Memoir 9, July 1916. 



