30 BOARD OP AGRICULTURE. 



preferred by cereals, is nitrogen ; by leguminous plants — poiassa ; 

 by roots — i^liospliates ; we say the preferred, but not the exclusive; 

 for these three substances, in various proportion, are necessary to 

 each and all, and even lime, which humus renders assimilable, 

 must be added." 



" By adding, according to M. Ville's system, nitrogenous 

 matter, phosphate of lime, and potassa — that is to say, a normal 

 or complete manure to calcined sand, the seed-wheat, being equal 

 to 1 — the crop is represented by 23." 



"Upon withdrawing the nitrogenous matter from this mixture 

 of the four elements, the crop fell to 8.83." 



"Upon withdrawing the potassa, and retaining all the others, 

 the crop only attained to the figure 6.57." 



" When the phosphate of lime was omitted, the crop was 

 reduced to 0.71 ; vegetation ceased, and the plant died." 



" Lastly, upon abstracting the lime, then the crop, the maximum 

 of which was represented by 23, was only 21.62." 



"From the above facts we draw these conclusions: " That if 

 the four elements of a perfect manure, above named, act only in 

 the capacity of regulators of cultivation, the maximum effect they 

 can produce implies the presence of all four. In other words, the 

 function of each element depends upon the presence of the other 

 three. When a single one is suppressed, the mixture at once 

 losses three-fourth of its value." 



" It is to be remarked, that the suppression of the nitrogenous 

 matter, which causes the yield of wheat to fall from 23 to 8.33, 

 exercises only a very moderate influence upon crops, when the 

 plant under cultivation is leguminous. But it will be quite other- 

 wise if, in such cases, we remove the potassa." 



" If we extend the experiment to other crops, and successively 

 suppress from the mixture one of the four agents of production, 

 we ai-rive at the knowledge of the element which is most essential 

 to each particular crop, and also which is most active in com- 

 parison with the other two. For wheat, and the cereals generally, 

 the element of fertility par excellence — that which exercises most 

 influence in the mixture, is the nitrogenous matter. For legumin- 

 ous plants potassa, for turnips and other roots, phosphate of 

 lime." 



" Suppose we wished to cultivate wheat indefinitely. We 

 should at first have recourse to the complete manure, and after- 

 wards administer only the dominant element, or niti'ogenous 



