148 BOARD OF AGRICULTURE. 



especially those who are accustomed to observe plants in house 

 and pot-culture, recognize in nature something akin to it in a 

 large number of plants, and can secure the highest success in 

 their vocation only by a change of soil periodically, or a change 

 of crop when the plants shall indicate that deleterious influ- 

 ences are at work. Nature is as regardful also of the physical, 

 as of the chemical condition of the soil, and the two influ- 

 ences are in her working intimately united. Chemical in- 

 fluences are ineffective unless the physical state is such as to 

 bring it fully under their power. Plants growing on the soil 

 have great influence in this regard, but some much more than 

 others. Some give the soil shade and protection from the in- 

 fluence of the sun and wind, retarding decomposition, aiding 

 carbonization and preserving its moisture. Some send their 

 feeble rootlets to but little depth, and only in the friable earth, 

 while others penetrate, and by their expansive power open the 

 soil to great distances, bring up the fertilizing material from 

 below, fill the whole soil with their fibrous network, and then 

 by decay give to it large quantities of organic material to impart 

 color, absorbing and retaining power to the whole mass. A 

 change of plants enables us to secure these different influences 

 as the soil shall require them to assist the chemical forces in 

 the more rapid development of plant-food. 



I have thus endeavored to indicate some of the natural laws 

 which point to crop rotation as one of the aids of which we 

 may avail ourselves, to preserve or improve the producing power 

 of the soil when the crops are removed for animal sustenance. 

 But science and practice both completely demonstrate that 

 they are only aids. No system of rotation has ever yet been 

 discovered, and I have grave doubts if it ever will be, that will 

 enable us to remove annual crops from the soil without deplet- 

 ing it. We may grow a potash-plant until it will grow no 

 longer, and the soil is specially exhausted, for that class of 

 plants. Then we may take the lime-plant and so through the 

 entire list of special feeders, and at the conclusion of the 

 round we shall find a soil suffering either from general exhaus- 

 tion, or so deteriorated as to scarcely pay the cost of cultivation. 

 English farmers, amateur and practical, have tried crop rotation 

 as a cvu'e for sterility a whole generation with the most unsatis- 

 factory results and with an endless diversity of opinion as to 



