CULTIVATION. 21 



" Every one understands tliat a fertilizer acts upon the 

 plant to supply it with food, and to favour its growth ; 

 everybody is also convinced that some fertilizers act 

 upon the soil, improving its texture and composition and 

 increasing its fertility. It is an equally well ascertained 

 fact that the soil acts upon fertilizers to modify their 

 effect. A very wet or very dry soil is known to nullify 

 the benefit which might be expected of a fertilizer in a 

 simply moist soil ; but more than this, more than by the 

 accident of external circumstances, it is a fact that each 

 kind of soil has a special action of its own on fertilizers, 

 so that if it were asserted of two soils, which, unmanured, 

 were of equal fertility, that a given fertilizer applied to 

 both, greatly improved the crop on one, and had little 

 effect on the other, such a statement might not only be 

 accepted as a fact, but an explanation might be given in 

 general terms for such a fact. 



" Now experiments have shown that different soils when 

 mixed with like quantities of various fertilizing elements 

 and then treated with water, in imitation of rain, 

 manifest very different behaviour toward the admixed 

 substances. One soil will lay hold of the potash in a 

 fertilizer, and fix it in a kind of chemical combination so 

 firmly that water can dissolve it but with extreme slow- 

 ness ; another soil puts its grasp on the lime of a fertilizer, 

 and at the same time allows potash which belongs to itself 

 to be dissolved out freely. There is, in fact, always a 

 complicated series of changes set in operation whenever 

 any fertilizer is incorporated with the soil, be it animal, 

 vegetable, or mineral ; be it alkali, acid, or saline ; be it 

 made on the farm or imported from abroad ; be it natural 



