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X. — On some points in Agricultural Chemistry. By 

 Justus von Liebig. 



In the years 1840 and 1842 I expressed the opinion that the 

 natural sources of the nitrogen necessary to plants are not suffi- 

 cient for the requirements of agriculture. But a series of 

 observations, as well as continued reflection on the subject, con- 

 vinced me that this opinion could not be maintained. 



As my work on Agricultural Chemistry contains only a very 

 small part of the experience and of the facts on which my con- 

 clusions are founded, I propose in the following pages to enter 

 more minutely into some of these details ; and I entertain the 

 hope that every reader will acquire the conviction that the con- 

 siderations which induced me, in 1843 (when the 3rd edition of 

 my 'Chemistry, in its application to Agriculture and Phy- 

 siology ' appeared), to give up the views above alluded to, whicli 

 I had previously entertained, are simple and incontrovertible. 



From a given surface of land we reap, in different cultivated 

 crops, according to the analyses which have been made, very 

 unequal quantities of nitrogen. If we assume that the amount 

 of nitrogen, reaped from an acre of land in the form of grain and 

 straw, is, in the case of rye, represented by 100 parts by weight, 

 then the same surface, one acre, yields of nitrogen — 



In Oats 114 parts. 



Barley 116 



Wheat 118 



Meadow hay .. .. 121 



Eape 212 



Peas 243 



Beans .. .. .. 270 



Clover 390 



Tumijjs 470 



, These numbers prove incontestably that peas, beans, and the 

 other fodder or green crops, yield more nitrogen than the grain 

 crops. Meadow hay yields about as much as grain, or a little more ; 

 but peas, beans, and clover, supply twice as much nitrogen as 

 wheat. Tliese crops — peas, beans, and clover — yield this in- 

 creased amount of nitrogen, ivithout the 7isc of nitro(fenised manure. 

 Nay, the produce of nitrogen can be even augmented still further : 

 in clover by the use of ashes and of gypsum ; in turnips by the 

 addition of superphosphate of lime. 



The source from which these crops obtain the nitrogen they 

 contain can be no other than the atmosphere. 



In practical cultivation, it is to grain fields that nitrogenised 

 manures are especially given. It is plain that the necessity for 

 supplying nitrogen to grain crops, such as wheat for instance. 



