403 



Such results, proving that jaundice of the grape is due to a high calcium 

 content are found^ frequently as are also observations as to the effectiveness 

 of the iron sulfate. 



The question now is, how to explain the injurious effects of calcium 

 and the beneficial action of the so-called iron compounds. Luedecke found 

 that the water coming from the lime soils of Rhenish Hessen has an alkaline 

 reaction, and he found that with an addition of some iron salt (iron sulfate 

 or ferric chlorid), the iron was precipitated. He, therefore, came to the 

 conclusion that, since plants are able to take up iron only in a dissolved 

 form, and since the alkaline water prevents its solution, the grape vines 

 suffer from a lack of iron in spite of the great amount of it in the soil ; they, 

 therefore, become icteric. Viala and Ravaz noticed the injurious action of 

 lime in a neutralization of the cell sap of the roots-. 



Until we have the results of further experiments, we must be satisfied 

 with the fact that large amounts of easily soluble calcium compounds will 

 produce icterus of the grape, and that abundant additions of iron sulfate 

 have often been found to be useful in combatting it. It is now of the first 

 importance to consider that the affinity of the sulfuric acid of the iron com- 

 pound for calcium is great and forms g>'psum which, only slightly soluble, 

 is proved to be non-injurious, or even beneficial to growth. 



Eger^ cites Oberlein-Beblenheim's experimental results, showing that, 

 on rich soils, fertilization with gypsum considerably increases the yield. 

 Since the addition of gypsum, made at the same time to poor soils, remains 

 absolutely without result, the favorable action of the gypsum may probably 

 he ascribed to its power of loosening up the soil. 



e. Excess of Potassium. 



Reference has been made already to the danger to soil constitution of 

 a continued heavy potassium fertilization, and in this it was emphasized 

 that lighter soils and moor soils responded more favorably to the addition 

 of potassium. Recently, however, Hollrung has called attention to another 

 disadvantage of all fertilization with mineral salts, — therefore, of potassium 

 salts also. He refers to Hall's experiments, showing an absolute change in 

 the water conditions in the soils. Hall determined (after 1866) the num- 

 ber of days in one year in which drainage flowed from an unfertilized field, 

 as contrasted with one constantly fertilized with Chile saltpetre. The 

 longer the drainage flows, the more water is removed from the field. Al- 

 though the results fluctuated in the several periods of five years each, which 

 he compared, yet as a whole for the entire length of time, they indicated 

 that in the "salted soils," larger amounts of water had passed into the 

 drainage through the subsoil. This makes possible conclusions as to an 

 unfavorable transformation of the soil. 



1 See V. Babo and Mach, Handbuch. des Weinbaues and der Kellerwirtschaft 

 Eger). 



2 See Eger. 



3 Ivoc. cit. p. 84. 



