m 



or nearly so, removed, while the other elements are in abundance. Sup- 

 pose in the first of these cases, that the farmer should, perhaps acciden- 

 tally, make use of lime as a special manure. The result would most 

 certainly show a great increase 'in the product. This seeming facility of 

 increasing the fertility of his soil induces him to repeat the application 

 of lime, and it may be with benefit even the second or third time ; but 

 while he is supplying only lime to his soil, he is removing in his crops, 

 other important elements, some of which soon become exhausted. The 

 farmer, if he does not understand the process, now wonders why his 

 ■crops fail ; he has applied abundance of lime, which before, gave such 

 evident increase in yield. But it is not lime that is now wanted ; it may be 

 soda or potash, or, phosphoric or sulphuric acid. Apply them and good 

 crops will again crown his labors. This view explains the beneficial re- 

 sults of potash or any special manure, as in the second case supposed ; 

 where sulphuric acid and lime were exhausted. Care should ever be exer 

 cised in the use of special manures, that other materials are also supplied. 

 What is called the rotation of crops is based upon the principles involv- 

 ed in the above remarks, for the theory of its action. All good farmers 

 know that the most ruinous system to fields that can be devised is to pro- 

 long the cultivation of the same crop upon the same field year after year. 

 Such fields can be restored to their former vigor and fertility only by 

 heavy and frequent manuring. This is too costly a process, however, to 

 be usually adopted. The one practised by every good farmer is the one 

 most in accordance with the principles of chemistry. After raising one 

 kind of crop for one, two or three seasons from the same field, by which 

 one or more elements of the manure applied may be supposed to be nearly 

 or quite exhausted, another crop of a different kind and requiring differ- 

 ent elements from those of the first, is then cultivated, for one or more 

 seasons, when a third, differing from the two former in its elements, may 

 be successfully cultivated. This series of crops may all perhaps be raised, 

 from one thorough manuring of a field, when, otherwise, it would have 

 required manuring as often as the crop has been changed in the case 

 mentioned. The great art in the rotation consists in selecting crops 

 belonging to the different classes above mentioned, such as grain crops, 

 root crops, and grass crops, each of these requiring a different material 

 and removing it from the soil. 



Suppose the farmer to have a soil which requires the application of 

 manure to render it fertile. He adds a good coating of manure and then 



