196 MANUAL OF MODEKN VITICULTURE. 



PAET II. 



SUBMERSION OF VINEYARDS. 



Submersion consists in flooding the whole surface of a 

 vineyard with water for a period sufficient to kill phylloxera. 

 This method can only be applied to vineyards established 

 in certain special conditions which we shall now study, 

 together with the installation necessary in practice and the 

 special cultural care necessitated. 



CHAPTER I. 



CONDITIONS NECESSARY TO THE SUCCESS OF SUBMERSION. 



These conditions are : 



1st. Possibility of procuring a sufficient quantity of water 

 at the right time without considerably increasing the cost. 



2nd. Application of water in regular sheets to soils 

 capable of retaining it. 



3rd. Use of varieties not suffering from this treatment. 



IST. WATEE. 



(A.) Quantity required. Submersion requires, as a rule, 

 very large quantities of water, varying according to the 

 permeability of the soil and the duration of the operation. 

 Formerly Faucon considered that 123,500 cubic feet per acre 

 were sufficient, but this figure must be considered as a 

 minimum, and it is greatly exceeded in most cases. We. 

 must reckon upon 353,000 to 530,000 cubic feet per acre, 

 and under some circumstances even 1,000,000 cubic feet 

 per acre. A part of this water must be delivered in a 

 constant flow to recuperate the loss by evaporation and 

 imbibition. 



(B.) Quality of water. Waters containing air, such as 

 those pumped by centrifugal machines or collected from 

 natural water-falls, are considered as less efficacious from an 

 insecticidal point of view, for the presence of a small num- 

 ber of air bubbles is sufficient to enable phylloxera to live. 

 Those completely deficient in fertilizing matters would 

 exhaust permeable soils during percolation through them. 



