SOIL COMPOSITION 



93 



TABLE 19. COMPOSITION OF SURFACE SOILS OF TENNESSEE 

 Average Pounds per Acre in 2 Million of Soil (about 6f -inch Stratum) 



from the southern point of Illinois, and that much of the upland 

 soil of northwest Mississippi is essentially of the same character. 



It will be noted that the average soil of the Central Basin is 

 comparatively rich in phosphorus, while the soils of the Highland 

 Rim, and more especially the sandstone soils of the Cumberland 

 Plateau, are extremely deficient in phosphorus, and the latter 

 is also very poor in potassium, as might be expected from its origin. 



The number of soil analyses entering the averages in Table 19 is 

 not sufficient for final data, but in the main they are supported by 

 larger numbers of analyses for acid-soluble plant food. Thus, the 

 averages of 25 analyses of soils from eight counties in the Central 

 Basin show 2020 pounds of acid-soluble phosphorus in 2 million 

 of soil, while 700 pounds of phosphorus is the corresponding aver- 

 age for 1 6 analyses of loessial soil from eleven counties in west 

 Tennessee. The acid-soluble phosphorus in the samples whose 

 total phosphorus content was determined (and thus afforded for 

 use in Table 19) was 1710 pounds for the Central Basin and 750 

 pounds for the. west Tennessee soil, 84 per cent of the total having 

 been dissolved by strong hydrochloric acid, in either case. On 

 this basis, the general average of all samples would show 830 

 pounds of total phosphorus for west Tennessee and 2400 pounds 

 for the Central Basin, in 2 million pounds of surface soil. 



Hilgard reports the average of 97 analyses of Mississippi soils 

 showing 790 pounds of acid-soluble phosphorus in 2 million pounds 

 of surface soil, but the more abundant upland soils average about 



