322 TALKS ON MANURES. 



and Gilbert clearly prove that a soil needs to be richer in available 

 phosphoric acid, to produce even a fair crop of turnips, than to 

 produce a large crop of wheat. And the experience of farmers 

 everywhere tends in the same direction. England is the greatest 

 turnip-growing country in the world, and you will find that where 

 one farmer applies potash to turnips, or superphosphate to wheat, 

 a hundred farmers use superphosphate as a special manure for the 

 turnip crop." 



"And we arc certainly warranted in saying," continued the Doc- 

 tor, " that the composition of a plant affords, in practical agriculture, 

 and on ordinary cultivated soils, no sort of indication as to the com- 

 position of tlie manure it is best to apply to the crop" 



" Again," continued the Doctor, " if the theory was a correct one, 

 it would follow that those crops which contained the most nitro- 

 gen, would require the most nitrogen in the manure. Beans, peas, 

 and clover would require a soil or a manure richer in available ni- 

 trogen than wh'eat, barley, or oats. We know that the very reverse 

 is true know it from actual, and repeated, and long-continued ex- 

 periments like those of Lawes and Gilbert, and from the common 

 experience of farmers everywhere." 



" You need not get excited," said the Deacon, " the theory is a 

 very plausible one, and while I cannot dispute your facts, I must 

 confess I cannot see why it is not reasonable to suppose that a 

 plant which contains a large amount of nitrogen should not want 

 a manure specially rich in nitrogen ; or why turnips which contain 

 so much potash should not want a soil or manure specially rich in 

 potash." 



"Do you recollect," said I, " that crop of turnips I raised on a 

 poor blowing-sand ? " 



" Yes," said the Deacon, " it was the best crop of turnips I ever 

 saw grow." 



" That crop of turnips," said I, " was due to a dressing of super- 

 phosphate of lime, with little or no potash in it." 



"I know all that," said the Deacon. "I admit the fact that 

 superphosphate is a good manure for turnips. "What I want to 

 know is the reason why superphosphate is better for turnips than 

 for wheat?" 



"Many reasons might be given," said the Doctor; "Prof. 

 Yoelcker attributes it to the limited feeding range of the roots of 

 turnips, as compared to wheat. ' The roots of wheat,' says Prof. 

 Ycolcker, * as is well known, penetrate the soil to a much greater 

 depth than the more delicate feeding fibres of the roots of turnips. 

 Wheat, remaining on the ground two or three months longer than 



