that a plant that contains in its crop-substance three and four 

 times as much nitrogen as another plant, requires for that reason 

 a more liberal quantity of nitrogen in the soil. But that time is 

 past. It has been found that the requirements of plants for 

 nutrition and for fertilization are by no means the same, and this 

 discovery has done much towards elucidating the subject by 

 directing the research to a closer study of plant-growth, that 

 is of the principle of plant-life. 



WHAT IS PLANT GROWTH? 



Now, plant-growth, if a definition is to be attempted, might 

 be defined as the transformation of inorganic into organic 

 substances. All plants, without exception, require mineral 

 substances out of which by means of certain raw materials the}' 

 form organic matter, viz. : the grains of wheat, barley, oats, or 

 the potatoes, beets, peas, tobacco leaves, cotton bolls, etc. 

 The mineral substances, viz.: phosphoric acid, potash, lime, 

 soda, etc., are furnished by the soil, while the air furnishes the 

 carbonic acid, the sky the water; nitrogen has, in many cases, 

 to be furnished with the mineral subtances by man. 



The problem of plant-nutrition narrows itself down, there- 

 fore, to the question of nitrogen, phosphoric acid and potash 

 (more correctly, kali), as nearly all other mineral substances 

 are, as a rule, in entirely sufficient quantities in any soil, with 

 the exception, perhaps, of lime. The absence of lime, how- 

 ever, manifests itself so easily and so surely, that for general 

 observations lime need not be taken into consideration. Where- 

 ever it forms an essential element it will be mentioned. 



WHEREIN CONSISTS RATIONAL 

 FERTILIZATION. 



Proper fertilization consists therefore in a thorough and 

 correct understanding of the nitrogen, the phosphoric acid and 

 the potash question. In that sense it has been taken up 

 by science, and in that sense it has been taken up by 

 all practical farmers. Science established, for instance, that 



