SUMMARY -DISCUSSION 
The significance of any organic molecule in contact with a soil depends upon the 
reactions or transformations that may take place in this new environment. Of most 
specific interest are: (1) The potentiality for breakdown whether biological, chemical, 
or physical, and the nature of the decomposition products, (2) the reactivity with soil 
constituents, (3) the retention in active or inactive forms, and (4) the movement either 
by leaching or volitalization. From the outset the purpose of this discussion has been 
to point out that the fate of this molecule depends not only on its properties, but also 
upon those of the soil and its physical environment. Soils have been shown to vary widely 
in chemical composition, properties, and physical environment. Examples have been 
cited to show how these changes in conditions may alter the behavior of organic mole- 
cules from soil to soil. To predict the fate of a given organic molecular species ina 
given soil will require, therefore, the integration of adequate knowledge pertaining to both. 
LITERATURE CITED 
(1) Allison, F. E., Sherman, M.S., and Pinck, L. A. 1949. Maintenance of Soil Organic 
Matter: 1. Inorganic Soil Colloid as a Factor in Retention of Carbon During the 
Formation of Humus. Soil Sci. 68: 463-478. 
(2) Dean, L. A., and Dean, A.L. 1929. Decomposition of Citric Acid by Soil. Soil Sci. 
28: 281-287. 
(3) Ensminger, L. E., and Gieseking, J. E. 1939. The Absorption of Proteins by Mont- 
morillonitic Clays. Soil Sci. 48: 467-474. 
(4) Ensminger, L. E., and Gieseking, J. E. 1942. Resistanceof Clay-absorbed Proteins 
to Proteolytic Hydrolysis. Soil Sci. 53: 205-209. 
(5) Foster, A. C., Boswell, V. R., Chisholm, R.D., Carter, R. H., Gilpin, G. L., Pepper, 
B. B., Anderson, W. S., and Geiger M. 1956. Some Effects of Insecticide Spray 
Accumulations in Soil on Crop Plants. U.S. Dept. Agr., Tech. Bul. 1149. 36 pp. 
(6) Gieseking, J. E., 1939. The Mechanism of Cation Exchange in the Montmorillonite- 
beidellite-nontronite Type of Clay Minerals. Soil Sci. 47: 1-13. 
(7) Hendricks, S. B. 1941. Base Exchange of the Clay Mineral Montmorillonite for 
Organic Cations and its Dependence Upon Adsorption Dueto van der Walls Forces. 
Jour. Phys. Chem. 45: 65-81. 
(8) Jenny, H., Gessel, S. P., and Bingham, F. T. 1949. Comparative Study of Decom- 
position Rates of Organic Matter in Temperate and Tropical Regions. Soil Sci. 68: 
419-432. 
(9) Pinck, L. A., Dyal, R. S., and Allison, F. E. 1954. Protein-montmorillonite Com- 
plexes, Their Preparation and the Effects of Soil Microorganisms on Their 
Decomposition. Soil Sci. 72: 109-118. 
(10) Pinck, L. A., Holton, W. F., and Allison, F. E. Antibiotics in Soils: I. Physico- 
chemical Studies of Antibotic-clay Complexes. Soil Sci. [In press] 
(11) Pinck, L. A., Soulides, D. A., and Allison, F. E. Antibiotics in Soils: II. Extent and 
Mechanism of Release. Soil Sci. [In press] 
(12) Ruehrwein, R. A., and Ward, D. W. 1952. Mechanism of Clay Aggregation by 
Polyelectrolytes. Soil Sci. 73: 485-492. 
(13) Schreiner, O., and Reed, H. S. 1907. Certain Organic Constituents of Soils in 
Relation to Soil Fertility. U. S. Dept. Agr., Bur. Soils Bul. No. 47. 52 pp. 
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