OF PLANTS BY MANURING. 49 



By manuring^ nourishment for plants is conveyed 

 directly into the soil. According to the preceding 

 chapter, we have to consider as nourishment all those 

 bodies which are able to furnish plants with one or 

 more of the chemical elements necessary to their 

 growth. Here it is, however, to be expressly pointed 

 out, that a plant can only grow vigorously, thrive, 

 and attain fully to maturity, when these chemical ele- 

 ments are supplied all together. As the life of man 

 ceases when any one of the conditions requisite to 

 its continued existence — for example, air (oxygen) 

 or water — is withdrawn, — as the works of a clock 

 stand still when only a single little wheel is taken 

 from them, — so also the complete development of a 

 plant is checked, although but one of its necessary 

 elements is wanting. Hence it follows that we can 

 only regard such manures as in a strict sense perfect 

 or complete, which contain all these constituents. 

 Hence, moreover, a multitude of often entirely con- 

 tradictory results, in agricultural trials of one and the 

 same manure, are explained in a very simple manner. 

 Lime, gypsum, bone-dust, etc. act excellently on 

 many kinds of soil ; on others, not at all. If a soil 

 contains a sufficiency of lime, then manuring with 

 lime will answer no good end ; for the plant, finding 

 enough of this constituent already in the ground, re- 

 quires no further addition of this substance. On the 

 other hand, in land poor in lime or altogether with- 

 out it, such a manuring may furnish extraordinary 

 results, because it remedies an actual deficiency of 

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