172 THE ALTERNATION OF CROPS. 



agriculture is to produce either articles of commerce, 

 or food for man and animals ; but a maximum of 

 produce in plants is always in proportion to the 

 quantity of nutriment supplied to them in the first 

 stage of their development. 



The nutriment of young plants consists of car- 

 bonic acid, contained in the soil in the form of 

 humus, and of nitrogen in the form of ammonia, 

 both of which must be supplied to the plants, if the 

 desired purpose is to be accomplished. The forma- 

 tion of ammonia cannot be effected on cultivated 

 land, but humus may be artificially produced ; and 

 this must be considered as an important object in 

 the alternation of crops, and as the second reason 

 of its peculiar advantages. 



The sowing of a field with fallow plants, such as 

 clover, rye, buck-wheat, &c., and the incorporation 

 of the plants, when nearly at blossom, with the soil, 

 affect this supply of humus in so far, that young 

 plants subsequently growing in it find, at a certain 

 period of their growth, a maximum of nutriment, 

 that is, matter in the process of decay. 



The same end is obtained, but with much greater 

 certainty, when the field is planted with sainfoin or 

 lucern.^ These plants are remarkable on account 

 of the great ramification of their roots, and strong 

 development of their leaves, and for requiring only 

 a small quantity of inorganic matter. Until they 

 reach a certain period of their growth, they retain 

 all the carbonic acid and ammonia which may have 

 been conveyed to them by rain and the air, for that 

 which is not absorbed by the soil is appropriated by 

 the leaves ; they also possess an extensive four or 



* The alternation of crops with sainfoin and lucern is now univer- 

 sally adopted in Bingen and its vicinity, as well as in the Palatinate j 

 the fields in these districts receive manure only once every nine years. 

 In the first years after the land has been manured turnips are sown 

 upon it, in the next following years barley, with sainfoin or lucern ; in 

 the seventh year potatoes, in the eighth wheat, in the ninth barley; 

 on the tenth year it is manured, and then the same rotation again takes 

 place. — L. 



