Selected Bibliography 147 



coinpouucls, such as aninionia and the salts of potassium, calcium, 

 and magnesium. Rapid changes in reaction to either higher or lower 

 acidity are also prc\ontod by the "bufrering" properties of soil or- 

 ganic matter. Plant poisons become less toxic in a soil high in 

 humus; high salt concentrations are less injurious; and aluminum 

 solubility, and thus its specific injurious action, are markedly de- 

 creased (Hester and Shelton). Plant deficiency diseases are usually 

 less severe in soils well supplied with organic matter, not only be- 

 cause of the increased vigor of the plants but also because of an- 

 tagonistic effects of the various soil microorganisms which become 

 more active in the presence of an abundance of organic matter. 

 Although some of these diseases may sometimes be controlled by 

 treatment of the soil with organic matter, the effectiveness of this 

 procedure cannot be fully relied upon in all cases. 



Selected Bibliography 



1. Albrecht, \V. A., Methods of incorporating organic matter with the soil in 

 relation to nitrogen accumulations, Missouri Agr. Expt. Sta. Res. Bull. 249, 

 1936. 



2. Alway, F. J., Changes in the composition of the loess soils of Nebraska 

 caused by cultivation, Nebraska Agr. Expt. Sta. Bull. Ill, 1909. 



3. Hester, J. B., and Shelton, F. A., Soil organic matter investigations ui^on 

 coastal plain soils, Virginia Truck Expt. Sta. Bull. 94, 1937. 



4. Jenny, H., Soil fertiht>' losses under Missouri conditions, Missouri Agr. Expt. 

 Sta. Bull. 324, 1933. 



3. Lipman, J. G., and Blair, A. W., Nitrogen losses under intensive cropping. 

 Soil Sci., 12:1-16, 1921. 



6. Lyon, T. L., Bizzell, J. A., and Wilson, B. D., Depressive influence of cer- 

 tain higher jjlants on the accmnulation of nitrates in soil, J. Am. Soc. Agron., 

 15:457-467, 1923. 



7. Russell, E. J., Plant Nutrition and Crop Production, University of California 

 Press, 1926. 



8. Russell, E. J., and Voelcker, J. A., Fifty Years of Field Experiments at the 

 Woburn Experimental Station, Longmans, Green & Co., London, 1936. 



9. Russell, J. C, Organic matter problems under dry-farming conditions, /. Am. 

 Soc. Agron., 21:960-969, 1929. 



10. Shutt, F. T., Influence of grain growing on the nitrogen and organic matter 

 content of the western prairie soils of Canada, Can. Dept. Agr. Bull. 44, 

 N.S., 1925. 



11. Smith, N. R., and Humfeld, II., Effect of rye and vetch green manures on 

 the microflora, nitrates, and hydrogen-ion concentrations of two acid and 

 neutralized soils, J. Agr. Research, 41:97-123, 1930. 



