MANUAL FOR SUGAR GROWERS. 



food not readily dissolved by plant-roots, but which 

 by the action of the atmosphere is slowly brought 

 into such a condition as to be capable of being dis- 

 solved ; we can thus divide the plant-food into that 

 which is available and that which is slowly avail- 

 able. In a chemical analysis it is usual to regard 

 those constituents which are insoluble in cold dilute 

 acid, but which are soluble in warm strong hydro- 

 chloric acid, as slowly available. This slowly avail- 

 able plant-food is by no means to be overlooked in 

 forming an estimate of the value of a soil, as it con- 

 stitutes a kind of capital and indicates that soils 

 possessing an abundant store will yield abundant 

 crops with the minimum of manure, or of that 

 special constituent which happens to be present. 

 Below is given a comparison of the amount of cer- 

 tain substances soluble in dilute and strong acids, 

 respectively, in certain soils. 



Where no crops are removed from the soil, as in 

 the case of forests and prairies, the fertility of the 

 soil will actually increase from year to year, owing 

 to the gradual conversion of the slowly available 

 into the available mineral plant-food ; at the same 



