220 PLANT-FOOD AND AGRICULTURE. 



PLANT-FOOD AND AGRICULTURE. 



By E. Lewis Stdktevant, M.D. 



[From the Report of the Connecticut Board of Agriculture, 1876 ] 



The soil contains the food of plants. The plants assimilate this 

 food, and combining it with supplies obtained from the air, through 

 their vital forces, build up their structure which is to supply food 

 for man. There is therefore a close relation between the soil and 

 the plant, and between the plant and the man. 



We have a difierence between the natural field and the aarricul- 

 tural field, and the difference is brought about through the relations 

 of man. In the natural field there is no renewal of product by 

 man, while in the agricultural field there is renewal. The natural 

 field wastes little or none of the food elements, but rather accu- 

 mulates ; the natural crop containing but little plant-food compared 

 to the artificial. The artificial field has to annually supply large 

 quantities of its fertile elements to the plants for removal from the 

 land. A ton of wood contains about three pounds of potash, the 

 ton of barley fodder about eighteen pounds ; the ton of loaves 

 returns to the soil say four pounds of potash, the ton of growing 

 wheat removes fifteen pounds. We may, therefore, cut woodland 

 and yet grow woodland without fear of failure from deficient plant- 

 food, for the growth of our wood contains but little ash element 

 and but little nitrogen, and disintegration more than keeps apace 

 with the wants of the trees. The cultivated crop, on the other 

 hand, removes considerable ash element, and much nitrogen. In 

 the one case the farmer removes principally what is furnished by 

 the air, in cheap abundance ; in the other case he is removing 

 what is very costly. 



Ilence in Nature a continual addition to the surface mould from 

 the falling leaf and the decaying growth, and a gradual thickening 

 of the surface soil or loam. Fertility is being continually stored 

 in a form which protects against loss by evaporation and drainage 

 in large degree. Under cultivation a continual abstraction, for 

 man's use, of the fertility which has been prepared by the natural 

 agencies of the past, and which is being added through decompo- 

 sitions and rainfall. Under this process, not only is there an 



