No. 105.] 213 



the same wheat which, with vegetable manure only, gave scarcely 10 

 per cent, of gluten, yielded more than three times as much when 

 manured with powerful animal substances, rich in ammonia. Some 

 varieties of the potato are found to contatn more starch than other 

 varieties ; and this quantity is also controlled to some extent by 

 soil. 



The analysis of plants will also indicate what plants are best to 

 employ as manure by plowing in the green crop. A considerable 

 portion of nitrogen is essential to the growth of wheat. Now clover 

 is also found to contain a large portion ; hence a crop of clover be- 

 comes eminently useful as manure for this grain. Wheat abstracts 

 its nitrogen chiefly from the soil, and is consequently exhausting ; 

 clover obtains it mostly from the air, and is not exhausting, but becomes 

 in this way the provider for the wants of the wheat. 



Analysis has also proved that in addition to the usual organic ele- 

 ments, there are about ten organic or earthy constituents, most of which 

 are invariably found in the same species, and are indispensible to its 

 healthy growth. These are potash, soda, lime, magnesia, alumina, 

 silica, iron, manganese, sulphur, phosphorus, and chlorine. These 

 substances are derived by the plants from the soil ; hence a fertile 

 soil, — one from which plants may draw these essential constituents, 

 must of course contain them. Here the intimate relation between 

 the constituents of plants and of soils is at once obvious. Hence 

 soils which are destitute of a part of these ingredients, or contain 

 them in very small proportions, is necessarily sterile ; or if they be 

 destitute of one only, the same result must take place, if that one is 

 an essential ingredient to the crop growing upon them.* And here 

 it is that the great benefits to be derived from analysis of soils, at 



* Those plants, says C. W. Johnson, which yield salt, never grow well on lands 

 which do not contain it; those in which carbonate of lime is found, never flourish in 

 soils from which this is absent. Plants which abound with nitrate of potash, such as 

 the sun-flower and the nettle, always languish in soils free from that salt; but when 

 watered with a weak solution of it, their growth is very materially promoted, and 

 saltpetre is then found in them, upon analysis, in very sensible proportion. The same 

 writer states, that an old pasture became, in spite of various liberal top dressings of 

 difierent manures, incapable of producing a luxuriant crop. At last peat ashes were 

 found to produce the best result, or an increase of more than a ton of hay per acre. 

 These peat ashes were found to contain one-eighth of their weight of gypsum, which 

 was the ingredient the soil needed. Gypsum itself was then applied with the same 

 successful result. 



