The author experimented on the environmental conditions in the artificial light room of the phytotron at the Hokkaido Agricultural Experiment Station to make clear the distribution of air velocity, air temperature, radiation energy and influence of vegetation on these factors.
Air is provided into the room from the perforated side wall and expelled into the opposite wall of same style. At the standard condition which has no pot-trolley and soybean plants in the room, the fairly uniformal distribution of air velocity and temperature are measured. Along air stream from the supply wall to the return wall, air temperature rises only 0.6°C in the standard condition. At the growing condition which has pot-trolleys and soybean plants, the air temperature between plants rises in the range from 1.4 to 1.9°C according to the distance from supply wall. This elevation of temperature is primarily owing to the insufficiency of air velocity. To depress this phenomenon, more sufficient air velocity should be secured.
Soybean plant height varies from 48 to 111cm with their places. Under favourable conditions, stem elongation is accelerated to receive more radiation energy from the lamps, causing as much as a three times difference in the enlargement of plant height.
The soybean growth was comperatively tested at the artificial light room, at the natural light room and at outdoors. It was proved that the environmental conditions in artificial light room were inferior to the outdoor conditions, but superior to the conditions in natural light room from the view of the increment of dry matter per day, grain yield and its component characters such as pod number per plant and grain weight.
Normal growth processes from germination to maturity are attained under the condition of this artificial light room.

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The author measured the air change and the thermal balance of a phytotron (1) on fine day in April.
1. The humidity variation in the growth room was quantitative to the generation of steam from a evaporative pan. The diurnal variation of humidity was found in the glass room where the plants transpired following to solar radiation.
2. The air change was measured by the tracer gas method (2) . The natural air change was 0.9 times per hour. The air change in normal operation closing the fresh air damper was 3 times per hour. The going and coming air leak were found due to the fan operation at the glass roof in growth room and at the door between room and corridor.
3. The needed steam quantity to humidify the circulating air was large as several tenfold than the steam quantity which is enough to humidify the room air. This shows that the air tight improve-ment is important at the humidity control of this phytotron.
4. The thermal balance was calculated from the data measuring 9.00-14.30 on 23th. April of the primary brine temperature (inlet and outlet), the secondary brine temperature (inlet and outlet), solar radiation, the temperature and humidity of room air and fresh air, the consumption of electric power and liquid fuel, etc.
Thermal loss at fan was comperatively large as 36 per cent.
The reduction of the thermal loss at pump (8 per cent) and at duct (5 per cent) would be practicable.

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The influences of mulching methods on soil moisture, soil temperature, and tobacco growth were studied. Clear polyethylene film of 95 and 120 cm width and black polyethylene film of 95 cm width were used as mulching materials, and six kinds of ridges were made in tobacco field at the Okayama Tobacco Experiment Station. They were as follows ;
1) Unmulched ridges (no mulch)
2) Uumulched ridges high (no mulch high)
3) Ridges low at start and heightened by soil dressing being covered with film of 95 cm throughout cultivation (mulch)
4) Mulched high ridges (mulch high)
5) Mulched high ridges covered with wide film (wide mulch high)
6) Mulched ridges covered with black polyethylene film (black mulch)
Soil moisture level was adequate for tobacco growth during days transplanting on April 2 to beginning of May. After middle of May at mulch and mulch high, where lower limits of film were kept open and water was admitted to evaporate from soil surface into open air, soil moisture tension rose above pF4.0-4.5. When soil moisture tension rose above pF4.5, ordinary rainfall did not increase soil moisture beneath film mulching.
At the early growth stage of tobacco, soil temperature and dry matter production of tobacco were highly correlated.

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