2i 



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 di\T.de 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 Avill yield abundant 

 crops A^dth 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 feiiilit}^ 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 



