On the Consumption of Water in Rice Fields. 



BY 



I. Inagaki, JVo<;aktishi, 

 Professor of A'^rictilturc in the ITtglier Xormal School, Tokyo, 

 ll^ith plate XV. 



It is well known that rice requires more water for cultivation 

 than other cereals, but there is as yet no quantitative study on the 

 subject. I tliereforc undertook to measure during the main 

 vegetative period of rice (June i8 — October 20) last year at in- 

 tervals of 2 or 3 days, tlie quantity of water evaporated from the leaves 

 and stems of the rice plants in the field of the College of Agriculture. 

 The apparatus I used for this purpose is roughly shown in figure I, 

 Plate XV, in which (W) is the outer wall of a room, and (A), a part of 

 the apparatus, is placed outside the house in the open air, while (B) is 

 placed in the room. (A) is a cylindrical zinc pot having the diameter 

 of 25 cm, in which one batch of rice is planted. The height of the 

 pot-stand can be regulated by means of three screws. (B) is a very 

 long (1.5 m) cylindrical zinc bottle in which a certain quantity of water 

 is always kept and carrying a graduated gauge (a) by means of which 

 the height of the water can be easily measured. This bottle is thus 

 simply a modification of a Mariotte's bottle. If we place the lower 

 end of the tube (b) on the same level as the surface of the vv^ater in 

 IDOt (A), the water of the pot will remain at a constant level. As the 

 water evaporates from the pot, an equal quantity passes into it from 

 bottle (B) through tlie tube (c) ; so that we can measure the water 

 evaporated from the pot byircading off its diminution in (B). But 

 as the quantity of water evaporated from the pot is not altogether 

 equal to that of transpiration from the plant, we must deduct 

 from the measurement thus made the quantity of water, evaporated 

 from around the stems of the plants. This is done approximately 

 by measuring the area of the water surface in the pot at 

 intervals of 2 or 3 days and calculating the corresponding evapo- 

 ration of water by means of a common evaporimeter placed by the 



