CONSUMI'TIOX OF WATER IN RICE FIELDS. 



From these figures we see that the quantity of water required 

 for rice culture is : 



max. mill, average. 



1.447 0.743 1.068 Htre per ha, per second. 

 Hence I conckide tliat the consumption of water in rice fields is 

 smaller here in Japan th.an in Italy, where, according to Cav. 

 Patriarca,"' the following quantities are required for irrigation': 

 On very heavy soil 2.081 litre per ha, per second 



On heavy soil 2.398 ,, ,, ,, ,, ,, 



On mean soil 3-486 ,, ,, ,, ,, ,, 



On light soil 4.773 ,, 



mean 2.637 litre per ha, per second. 



This difference in the two countries is mostly due to the 

 difference of climate, especially of moisture in the air. I can not 

 say^ at present that the transpiration from rice plants is much affected 

 by climate, but the evaporation from the v/ater surface must vary, 

 of course, with the hygroscopic conditions of air. In Japan the air 

 in summer is very richly loaded with the moisture (76 — 94 % on an 

 average during summer) carried hither by the S. and S.W. monsoon 

 from the Pacific Ocean. In Italy the case is quite different. There 

 prevails in summer a S. wind, which is naturally very dry, coming 

 as it does from the hot continent of Africa over the Mediterranean 

 Sea. Moreover, the wet Avind coming from the north is entirely in- 

 tercepted by the Alps, and the moisture is mostly condensed, 

 leaving only a moderate quantity to pass over the peninsula during 

 summer (dampness being 52 — 69 



The moist condition of the air in Japan leads me to believe that 

 this country is favorable to the cultivation of the plant, because the 

 vapor in the atmosphere not only diminishes the loss of the Avater 

 of irrigation, and gives us a natural advantage but also gives off its 

 heat of condensation to the soil at night and thus protects the plant 

 from the injurious effect of nocturnal cooling. The temperature is, 

 however, (relatively) lov.er in Japan than in Italy, being influenced 

 by that of the neighboring Asiatic continent. Why the rice, despite 

 of this, can be cultivated so far north as 43", where the mean tem- 

 perature in summer is only 18.5" C, is explained b}- three reasons, 

 viz : — 



(l) Severe cooling at niglit is avoided by the heat of condensa- 

 tion of atmospheric vapor. 



(i) Vergl. Markus, d. laixlw. Meliorationswcsen 1881. S. 59 



