402 



By neutralizing the acids of the plant roots the available phosphoric 

 acid will not be so largely absorbed. The great difference between the 

 action of calcium carbonate and that of gypsum is due to the fact that 

 g}'psum is taken up from the soil only so far as it is soluble in water (i. e. 

 in the very sHghtest amounts), while the absorption of the carbonate by the 

 plant depends upon the carbonic acid of the root. 



Excess of Calcium With Grapes. 



Since the introduction of grapes grown on budded American vines 

 there have been very many complaints of Jaundice. The disease is de- 

 scribed usually as "Chlorosis" ; but according to my conception it must be 

 called "Icterus." 



Of course, the causes of the yellow condition of the foliage of grapes 

 may differ very greatly, as in other plants. Very frequently, root decay, 

 occurring with or without fungi, plays a role in heavy soils. Vitis Riparia 

 and V. rupcstris, with their w^eaker root systems are especially sensitive to 

 such soils, while varieties with strong roots (Jacquez, Herbemont, etc.), 

 better adapt themselves^. American vines, however, are grown with great 

 difficulty on soils containing a great deal of calcium in an easily foluble form 

 and not rich in nutrients. In France it was possible to collect the greatest 

 amount of information on this subject. Luedecke- repeats the results of 

 soil investigations which the agricultural society of Cadillac undertook in 

 1890. The soil which showed no jaundice of the vines and that which 

 showed jaundice contained 



No jaundice jaundice 



Phosphoric acid 0.07 per cent. 0.06 per cent. 



Potassium 0.39 per cent. 0.37 per cent. 



Calcium 1.81 per cent. 18.93 P^^ cent. 



Ferric oxid 5.90 per cent. 3.02 per cent. 



Nitrogen o.io per cent. o.io per cent. 



The content of both soils in nitrogen, potassium and phosphoric acid, 

 therefore, is about equal ; the ferric oxid percentage is high in botli, but 

 the calcium is nearly ten times as great in the soil producing jaundice. Tn 

 the fertilization experiments undertaken with Chile saltpetre, ammonia, 

 superphosphate, potassium chlorid, magnesium sulfate and iron sidfate 

 (ferric sulfate), only the last gave any satisfactory results. In this ex- 

 perimental plot, the vines formed a great many new roots. The same re- 

 sults were again obtained under similar conditions on soils naturally rich 

 in iron, in which, therefore, the favorable action of fertilization with iron 

 sulfate cannot be ascribed to a previous lack of iron. 



1 Eg-er, E., Untersuchungen liber die Methoden der Schadling-sbekampfung- 

 usw. Berlin, Paul Parey, 1905. 



- Luedecke in Zeitschr. f. d. landw. Ver. d. Grossherz. Hessen 1892, No. 41, 

 1893, No. 2. 



