158 



When the four Northern soils are compared, as a group, with 

 the four Southern soils, it is clear that much larger yields are 

 associated with the power for larger absorption of potash and of 

 total salts, and with the larger solution as well, where that has 

 taken place. In the case of the individual members of the North- 

 ern group, too, the yields and absorption of total salts rise and 

 fall somewhat together. The Selma Silt Loam and the Sassa- 

 fras Sandy Loam, each of which is a stronger soil than its mate, 

 have also a larger total absorption. 



If water-soluble salts carried by soils are important factors of 

 yield, and if the absorbed salts are still recoverable by degrees 

 under field conditions, and available to crops, some such rela- 

 tions as have been pointed, out should be expected to exist be- 

 tween the more and the less fertile soils. 



ABSORPTION" OF SALTS BY 8 SOIL TYPES FROM A SOLUTION OF 



ACME GUANO. 



In another series of trials fresh field samples were washed in 

 two ways, by percolation and by shaking in bottles, using a solu- 

 tion prepared from the acme guano, which had been applied to 

 the fields at the rate of 300 Ibs. per acre, on a series of the sub- 

 plots on each of the 8 soil types. 



The composition of the solution, as used upon the soils and de- 

 termined by the methods employed, is given in the next table, 

 where the amounts are stated in terms of the solution and in 

 parts per million of the dry soil, on the basis that all the salts 

 found in the solution added to the soil are absorbed by it. The 

 usual ratio of 5 of solution to 1 of soil was observed. 



Salts in solution of acme guano. 



In this series, as in the last, the surface foot, only, of each 

 soil type has been treated to the solution. It should be stated, 

 also, that to this solution, as in the last, potassium nitrate was 



