phosphoric acid, in order to produce perceptible immediate 

 results upon any crop, must be given to the plants in an avail- 

 able form;- and so with potash and with nitrogen. The very fact 

 that many State laws do not admit fertilizers for sale, unless 

 they contain certain percentages of these elements in a form 

 available to the plants, serves as a proof, if any were needed, 

 that the farmer's interest lies in procuring such plant- food as 

 science has established beyond gainsaying to be valuable as 

 plant-food, and that the farmer's interests are properly protected 

 by these State laws against imposition by unscrupulous parties. 

 Yet, while this protection of the farmer appears in a most 

 favorable light in one sense, it checks agricultural progress in 

 another sense. Hardly two soils are alike, and if two were 

 exactly alike, location and other circumstances might alter their 

 requirements entirely. Yet, .considering all ciraumctsnces, the 

 fertilizer-laws of the several States require only to be made 

 more uniform, and to be placed upon a more scientific basis than 

 that upon which some of them rest at present, in order tp attain 

 the purpose for which they have been framed, namely, the pro- 

 tection of the most vital interest of the country, its agriculture. 



THE REQUIREMENTS OF NUTRITION AND 

 FERTILIZATION ARE NOT THE SAME. 



The problem of fertilization and its solution depends, as has 

 been stated, upon a thorough knowledge of plant-growth and 

 plant-nutrition. It has also been remarked already that the re- 

 quirements of plants for nutrition and for fertilization are not the 

 same. Yery careful investigations of the process of plant- 

 growth and discoveries resulting from this research have thrown 

 an entirely new light upon the whole subject of fertilization. 

 To make, however, perfectly clear what will be said later on, 

 it is necessary to make here a few remarks about plant-growth. 



PLANT-GROWTH. 



A grain of wheat put into the ground germinates in due 

 course of time; it shoots out a tiny little leaflet, and this leaflet 

 feeds on the organic substance of the seed; it lives, as it were, 



