ROTATION OF CROPS. 253 



stituents and nitrogen being at command, these crops assimi- 

 late a very large amount of carbon from the atmosphere, and 

 produce, besides nitrogenous food products, a very large 

 amount of the carbohydrate — sugar — as respiratory and fat- 

 forming food for the live-stock of the farm. 



Very much the same may be said of maize as grown as a Assimiia- 

 fodder-crop in America, as of roots as grown in rotation in l ^ r °L n oy 

 other countries. Thus, there can be no doubt that the maize maize. 

 derives its nitrogen from the soil, collecting some time longer 

 than wheat, and availing itself of the nitrates formed after 

 the collection by the wheat has ceased. But, so far as the 

 product is consumed on the farm, much of its nitrogen is 

 recovered in the manure — the more when the food is used for 

 growing or fattening stock, and the less when for the produc- 

 tion of milk. 



The still more highly nitrogenous leguminous crops, on Legumin- 

 the other hand, although not characteristically benefited by ous fl^ s 

 nitrogenous manures, nevertheless contribute much more supply of 

 nitrogen to the total produce of the rotation than any of the nitrogen m 

 other crops comprised in it. It is also certain that, at any 

 rate a large proportion of the nitrogen of these crops is 

 obtained from the soil and subsoil ; though recent investiga- 

 tions have proved that some of their nitrogen, and sometimes 

 much of it, may be derived indirectly from the free nitrogen 

 of the atmosphere, brought into combination under the influ- 

 ence of micro-organisms within the nodules on the roots of 

 the plants. 



It is the leguminous fodder crops, and among them espe- 

 cially clover, which has a much more extended period of 

 growth, and much more extended range of collection within 

 the soil and subsoil, than any of the other crops of the rota- 

 tion, that yield in their produce the largest amount of nitro- 

 gen per acre. Much of this is doubtless taken up as nitrate ; 

 yet, the direct application of nitrate of soda has compara- Nitrate of 

 tively little beneficial influence on their growth. The nitric s ° da and 

 acid is probably taken up chiefly as nitrate of lime, but pro- 

 bably as nitrate of potash also, and it is not without signifi- 

 cance that the high nitrogen-yielding clover takes up, or at 

 least retains, very little soda. The general result is, then, 

 that although undoubtedly the clover takes up a good deal 

 of its nitrogen as nitrate, this would seem to be derived from Sources of 

 accumulations within the soil, which are brought into suit- T^Xwr 

 able conditions of combination, and distributed through a 

 wide range of soil and subsoil. 



So much, then, for the benefits of rotation, so far as the 

 requirements, the habits of growth, and the capabilities of 



