THE SOIL. 315 



cult and complicated to be attempted by any but a practical 

 agricultural chemist. 



The value of soil analysis, even when made by the most 

 careful and skilful chemists, is practically very little. The 

 quantity of matter which is capable of affording food to 

 plants is so very small, in proportion to the whole bulk of 

 the soil, even in those of the most fertile character, that it 

 is questionable whether a sample to be analyzed could be so 

 carefully prepared as to represent the average character of 

 the whole field. Then, again, if we were to procure a cor- 

 rect analysis of a very fertile soil, and then were to crop it 

 for a series of years without manure until it refused to pro- 

 duce paying crops, and were to have it analyzed again, it is 

 not likely that the chemist would detect any change in its 

 composition. In like manner, if we were to add to it 500 

 Ibs. to the acre of bone dust, enough to make it produce 

 abundantly, analysis would fail to detect the small quantity 

 of phosphate of lime that we had added in the bones. 



Another argument against the value of the analysis of the 

 soil, and a very strong one, is found in the fact that the fer- 

 tility of the soil depends less on the quantity of plant food 

 that it contains than on its condition. The roots of plants 

 cannot feed on the inside of a pebble ; they can only apply 

 their pumps to its surface and take in so much of what is 

 there exposed as can be dissolved in the moisture which goes 

 to form their sap. Neither can roots travel about in the 

 soil ; they grow into certain places, and there they remain. 



