USES OF BASIC SLAG 191 



foods in the soil into forms which the plant may take up readily. 

 So powerful is its action in this direction that it is often spoken 

 of as "a chemical plow." 



VI. The large amount of iron in the basic slag should not be 

 overlooked. "Iron," says Prof. Sorauer, in his excellent treatise 



on the physiology of plants, "is necessary in the building of chloro- 

 phyll," the substance that gives the green color to all foliage 

 "As it is the function of chlorophyll to form new plastic material 

 under the influence of the sunlight, it is natural that the absence 

 of iron, which is shown by the paleness of the leaves, should cause 

 a cessation of assimilation." 



This accounts for the deep green color and splendid healthy 

 condition of the foliage of the plants and trees fertilized with 

 basic slag. 



VII. In addition to all of the above, basic slag commends itself 

 strongly on account of the high degree of availability to plants 

 possessed by its phosphoric acid. While little or none of its 

 phosphoric acid is soluble in pure distilled water, it is soluble 

 in the secretions of the plant roots which feed upon it readily. 



Experiments indicate that the total phosphoric acid of basic 

 slag is practically as effective as the available phosphoric acid 

 of acid phosphate. 41 



It should be borne in mind that this high degree of availability 

 is not due to any treatment of the basic slag with sulfuric 

 acid. There is a marked reaction all over the country against using 

 acidulated fertilizers, as their continued use under improper con- 

 ditions has rendered many thousands of acres of valuable land 

 infertile. 



The average total results show that insoluble phosphoric acid, 

 that is phosphates which have not been treated or dissolved in 

 sulfuric acid (oil of vitriol), have more pounds of crop, both 

 straw and marketable grain, than the phosphoric acid in the 

 soluble and reverted forms ; that is, in phosphates which have 

 been dissolved in sulfuric acid. 42 



VIII. The comparative low cost of basic slag with resulting 



41 Ohio State Agricultural Experiment Station, Bulletin 100, 1899 : 137. 

 41 Maryland Agricultural Experiment Station, Bulletin 68, 1900 : 28. 



