SUBMERSION OF VINEYARDS. 



27 



that has to be done is to fill in the excavation with the dry soil placed 

 on one side, to spread it and rake it. Submersion is performed either 

 in winter or during the active period of the vegetation of the vine. 



A. Winter Submersion. — Winter submersion is a process which 

 cannot evidently be applied everywhere, and which requires special 

 conditions, of which the following are the principal : (1) The ground 

 must be slightly permeable, or very permeable but with an imper- 

 meable subsoil, such as is met with in the low plains of the French 

 coast, and in isolated spots in the river alluvial soils of some of 

 the chief water-courses. It is evident that too great a permeability 

 of soil would require too large a volume of water. The daily decrease 

 in the level of the water should not exceed a maximum of 10 centi- 

 metres (4 inches), a centimetre in depth corresponding to 100 cubic 

 metres of water per hectare, say 1404 cubic feet per acre. (2) The 

 ground ought to be perceptibly flat or very slightly inclined, a slope of 

 3 centimetres per metre (3 in 100) rendering submersion impracticable. 

 (3) The vineyard should be situated, if possible, near to a stream of 

 water, to an abundant spring, or to an artesian well, for it requires at 

 least 6000 cubic metres of water per hectare, 84,780 cubic feet per 

 acre. During the duration of the submersion, there is a daily loss 

 of water, not only from absorption by the soil but also from evapora- 

 tion into the atmosphere. The amount of water absorbed daily and 

 the duration of the submersion have been studied by Chauzit and 

 L. Tronchaud-Verdier, who have prepared the following table : — 



TABLE II. — Showing the Daily Loss of Water b\ 

 during Submersion. 



Absorption by Various Soils 



Evaporation into the atmosphere averages 6 millimetres in twenty- 

 four hours in winter, though it reaches 10 millimetres in summer. 

 (That is at the rate of an output of 1 litre per second per hectare, which 

 is calculated in general as the general output of the channels serving to 

 irrigate meadows.) (4) The duration and efficiency of the submersion, 

 moreover, depends on the climate. It is known that in France it can 

 only be practised in the centre and south. In the north the vines 

 would have to pass the winter surrounded by ice, which w^ould 

 seriously injure them. The duration of the submersion should 

 average sixty days in south and thirty days in central France. 



B. Submersion During the Active Period of the Vine. — Where 

 large quantities of water are deficient, summer irrigations, recom- 



