SOME RELATIONS OF ORGANIC MATTER IN SOILS VA 
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saeureproduktion. Centbl. Bakt. 2:28:45-89, 1910. 
SwANson, C.O. The loss of nitrogen and organic matter in culti- 
vated Kansas soils and the effect of this loss on the crop-pro- 
ducing power of the soil. Journ. indus. and eng. chem. 7 :529- 
532, 1915. 
SWANSON, C. O., AND LAaTsHAW, W. L. Effect of alfalfa on the 
fertility elements of the soil in comparison with grain crops. 
Soil sci. 8:1-39. 1919. 
WHEELER, H. J., Sarcent, C. L., AND HARTWELL, B. L. The 
amount of humus in soils and the percentage of nitrogen in the 
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Memoir 57. A Study, by the Crop Survey Method, of Factors Influencing the Yield of 
Potatoes, the fourth preceding number in this series of publications, was mailed on September 
22. 
