THE ORGANIC MATTBE OF THE SOIL 119 



the percentage of nitrogen in the soil is multiplied hy 20, a 

 rough idea of the amount of organic matter may be obtained 

 (N X 20 = organic matter). The following data from Rost 

 and Always illustrate not only the variations in organic 

 matter and nitrogen that may be expected in the surface and 

 subsurface of different soils, but the correlation between the 

 organic matter and nitrogen just mentioned: 



Table XXIV 



AVERAGE PERCENTAGE OF ORGANIC MATTER (C X 1.724) AND 



NITROGEN IN THIRTY REPRESENTATIVE MINNESOTA TILL SOILS 



FROM THREE SERIES. THE FIGURES FOR EACH OF THE 



THREE SOIL TYPES ARE AVERAGES OF TEN ANALYSES. 



Depth 



Forest 



Carrington 

 Loam 



Upland Prairie 



Carrington Silt 

 Loam 



Lowland 

 Prairie 



Fargo Silt IiOAM 





Organic 



Matter 



NlTBO- 

 GEN 



Organic 

 Matter 



Nitro- 

 gen 



Organic 

 Matter 



Nitro- 

 gen 



1 — 6 inches . . . 



7 12 '' 



13 24 '' 



25 36 '' 



5.34 



2.41 



1.38 



.86 



.253 

 .119 

 .078 

 .041 



7.96 

 6.00 

 S.ll 

 1.31 



.373 

 .285 

 .165 

 .062 



13.08 

 8.00 

 3.24 

 1.39 



.616 

 .385 

 .150 

 .054 



The following tentative classification of mineral soils on the 

 basis of their percentages of organic matter and nitrogen is 

 offered for generalized field use : 



Table XXV 



Description 



Low 



Medium , 



High 



Very high 



Percentage of 

 Organic Matter 



.0— 3.0 



3.0— 6.0 



6.0—10.0 



above 10.0 



Percentage of 



KiTROGEN 



.00-- .10 



.10— ,25 



.25— .40 



above .40 



^Eost, C. O., and Alway, F. J., Minnesota Glacial Soil Studies: I. A 

 Comparison of the SoiU of the Late Wisconsin and the lowan Drifts; 

 Soil Sci., Vol. XI, No. 3, pp. 161-200, Mar., 1921. 



