A.MMOXIA COLLECTED BY FODDER PLANTS. 



329 



rain, is upon tlie wliolc sufficient for liis cultivated plants, 

 but not enough for many of them in point of time. In 

 order to give a maximum crop, many plants require, 

 during the period of vegetation, much more than the air 

 and rain afford in that time ; and therefore the farmer 

 makes use of fodder plants in order to increase the crops 

 of his corn-fields. The fodder plants, which thrive 

 "without rich nitro2;enous manure, collect from the ground 

 and condense from the atmosphere, in the form of blood 

 and flesh constituents, the ammonia which is supplied 

 from these sources ; and the farmer, in feeding his horses, 

 sheep, and cattle with the tiurnips, clover, &c., receives, 

 in their solid and fluid excrements, the nitrogen of the 

 fodder in the form of ammonia and products rich in 

 nitrogen ; and thus he obtains a supply of nitrogenous 

 manures or nitrogen, which he gives to his corn-fields. 



The rule is, that for certain plants, weak in develope- 

 ment of leaf and root, and which have but a short 

 period of vegetation, the farmer must compensate by the 

 quantity of manure for the time which is wanting for 

 the absorption of the requisite amount of nitrogen from 

 natural sources. 



It is easy to see that the accumulation of nitrogenous 

 food by farm-yard manure in the uppermost layers of the 

 ground, so very important for the perfect growth of 

 cereal plants, must chiefly depend upon the successful 

 growth of fodder plants, 



Tlie unmanured fields in the Siixon experiments — 



