438 
0 N THE ACTION OF MANURES. 
BY BAKON LIEBIG. 
N O one will maintain that it is a matter of indifference to 
tlie husbandman, whether the ideas or principles which 
guide him in his operations are true or false. The success of his 
practice is evidently based on two things — that he knows what 
he is doing, and that he does the right thing in the right way ; 
so that, as every scientific view in agricultural matters becomes 
in its application a money question, it may perhaps be of 
interest to him to learn the exact state of our knowledge 
respecting the principles and theory of manuring. 
Science has taught us that plants require for their normal 
growth a number of elements (carbon, phosphorus, silica, 
ammonia, potash, lime, magnesia, &o.), most of which are 
furnished by the soil ; and it has been established by the direct 
experiments of Stohman and Knap that these various nutritive 
substances possess an equal nutritive value — that is to say, that 
all must exist together and work together in the building up of 
the vegetable fabric in its normal condition. Taking the case of 
those plants which supply food for man or beast, it is found 
that in the process of their nutrition none of these different 
substances can replace or discharge the functions of another ; 
so that, if one be wanting, although there may be an abundance 
of the rest in the soil, the plant cannot grow ; if one of them 
be insufficiently represented in the soil, the harvest will suffer in 
a certain proportion to the element that is wanting ; ammonia 
therefore possessing no higher nourishing or manure-value than 
lime, phosphoric acid no higher value than potash, &c. 
This doctrine, based on natural laws, is not generally ad- 
mitted by English farmers, and has even been stated to be 
inapplicable to English soils. Starting from the result of a 
number of experiments made on a small piece of ground,, a 
manufacturer of manure in London maintains, that there are 
degrees in the value of each of the nutritious elements in a 
manure, which could be easily determined, or estimated by the 
amount of cropsproduced on anyfield after being manuredwith it. 
If the produce were increased by one element and not by 
another, he concluded that the first possessed a preponderating 
value over the second. 
In his trial fields, for instance, phosphoric acid had little or 
