This study attempts simple linear and multiple regression analyses between the final grain yield of sorghum and the elements of climate for Kabba in the wet sub-humid climate of Nigeria during the different phenological periods of the crop's growth. It was found that fluctuations in air temperature and rainfall during the first 94 days of the sowing of the crop combine to reduce the final grain yield of sorghum at the station while rainfall supply during the pre-sowing period and temperature during the grain filling period tend to increase the final grain yield of the crop. The combined effect of the 4 climatic elements was found to account for 79.8per cent of the variability in sorghum yield at the station. The implications of the results obtained for sorghum farming at the station are also discussed.

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Stem heat balance method and Bowen ratio heat balance method were, respectively, used to determine transpiration (T) and evapotranspiration (ET) from a water-shortage free soybean field. Evaporation from the soil surface beneath the soybean canopy was indirectly estimated by subtracting T from ET. The diurnal change in the T/ET ratio was characterized by a parabolic curve with the minimum at noon, and higher values in the early morning and late afternoon, depending on the diurnal march of direct solar radiation intercepted by the canopy. Results showed that the evaporation from the soybean field at the early growing stage with sparse canopy was nearly equal to the evapotranspiration from the field at the later growing stage with dense canopy under a condition of enough soil moisture. The daily evaporation beneath the canopy decreased curvilinearly with the leaf area index (LAI). Combining the Makkink solar radiation model for estimating evapotranspiration and the transmission function of the canopy to global solar radiation yielded a simple model for estimating daily transpiration from the canopy. The transpiration estimated by this model increased curvilinearly with increment in the LAI. This relation was well approximated by a negative exponential function of leaf area index.

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The effects of the duration and intensity of artificial rainfall (mist) treatment on the growth of the kidney bean plants were investigated. Seedlings of the plants were exposed to four levels of mist treatment (Precipitation: 1-5mm/h) in a growth chamber (20°C, artificial short-wave radiation was regulated at 2.8MJ/m²·day) for several days (1-5days). The growth and injury of plants were examined immediately after the mist treatments, and when the plants were kept at 20°C in a phytotron for 2 weeks when the mean natural short-wave radiation amounted to 9.4MJ/m²·day after the treatments.
1) The growth measured immediately after a 1- to 2-day exposure to mist showed hardly any influence from the different mist treatments. However, at the end of five-day exposure at the heavy mist treatments (2 and 5mm/h), the dry weight of the shoot and leaf area decreased in comparison with those at the light treatments (0 and 1mm/h mist): there was no significant difference between the 2 and 5mm/h mist treatments. The degree of wilting after misting increased with increases in the duration and intensity of the treatment.
2) With a misting duration of 1 day, the weight and leaf area of the plants grown in a phytotron for about 2 weeks after the mist treatment were larger than those of plants grown in the phytotron throughout the experimental periods, but were markedly smaller when the misting was continued for 3 days or more. The three-day exposure to 1mm/h mist had no effect on subsequent growth, but a 2 or 5mm/h mist reduced the subsequent growth in fresh weight, dry weight and leaf area: the differences in the growth between the two treatments were small.
3) The promotive effect of short-term exposure to the mist treatment on growth was mainly attributed to an effect of weak light during the treatment rather than an effect of shoot wetting. However, the inhibitory effect of long-term exposure to mist was attributed to both effects of weak light and shoot wetting by the mist treatment.
4) These results suggest that the effect of shoot wetting by rain on growth mainly depends on the duration rather than intensity (amount) of rainfall.

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To estimate water loss from cultivated fields in the Northeast district of Thailand, we measured leaf transpiration and leaf stomatal resistance of several important crops, and calculated actual (AET) and wet environmental (PET) evapotranspirations in that district. AET and PET were estimated by Morton's method (1983) based on general meteorological data. The seasonal change in soil dryness index (DI) was calculated using these two evapotranspirations. The DI was very low in the rainy season, increased with time after the end of rainy season, and approached gradually to the value 0.7 to 0.9 in the mid-dry season. It was found that leaf transpiration and stomatal resistance of the major crops were also strongly affected by soil moisture conditions. We last studied the geographical distribution of the irrigation requirement using the dryness index and wet environmental evapotranspiration.

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A buried-tube-type heat exchanger is typical and simple for extracting heat from a compost bed except the requirement of some tedious works such as removing and retubing the tubes in remixing the compost materials. In order to simplify the above tedious works, a unique heat extraction method by a multi-heat-pipe heat exchanger was proposed. The analytical solutions of the temperature in the bed and the temperature of medium at the outlet of the heat exchanger were obtained. These solutions were mathematically similar to those for the buried-tube-type heat exchanger. Then, the heat extraction ability of the multi-heat-pipe heat exchanger was calculated from the solutions.

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The plantlets cultured under in vitro conditions of high relative humidity and low light intensity exhibit poor development of the epicuticular wax (Grout and Aston, 1977; Sutter and Langhans, 1979; Wardle et al, 1983) and photosynthetic system (Earle and Langhans, 1975; Grout and Aston, 1978). These plantlets are sensitive to environmental stress, especially water stress (Earle and Langhans, 1975; Hu and Wang, 1983). The transfer of in vitro-propagated plantlets to the external environment leads to damage or death for many crops, because of the dramatic changes in environmental conditions. Environmental control for acclimatizing plantlets is needed to overcome the problem. Therefore, the acclimatization unit was developed to control environment and to achieve high survival (low death) rates and rapid growth of plantlets. The description of this unit is as follows:
(1) With the acclimatization unit, temperature, humidity, light intensity, CO₂ concentration, air flow rate, and nutrient solution temperature etc. can be controlled (Figs. 1 and 2).
(2) A micro-computer is used to control the acclimatization unit, and to record, analyze the data.
The acclimatization unit can be used both for commercial purposes and for research purposes.
(3) The computer program for controlling the acclimatization unit is written in the BASIC language. The control logic to operate actuators is not included in the program but is given as data to the program. The logic is given in the form of control expression (Hoshi and Kozai, 1984). Therefore, changing the control logic is relatively easy.
(4) The environment inside the acclimatization unit is controlled on the basis of the acclimatization curves (Fig. 3). The curve for each environmental factor can be modified depending on the crop, and the season when acclimatized plantlets are transplanted to greenhouse or field conditions.
(5) By using the acclimatization curve, the diurnal change in the environment could be modified gradually day by day (Fig. 7).
(6) The trial run of the acclimatization unit showed that each environmental factor was controlled within a desired range (Fig. 4).
The test cultivation was done to investigate survival rate and growth rate of in vitro-propagated plantlets. The taro (‘Ishikawawase’) and the strawberry (‘Houkouwase’) after transferred from in vitro culture were acclimatized with the acclimatization unit and with the traditional method (described as control hereafter). In the traditional method, the growing space was covered with transparent plastic film and shading material.
(1) Death rate of plantlets of taro acclimatized with the acclimatization unit and with the traditional method were 8% and 23% respectively, and those of strawberry were 4% and 20% respectively.
(2) Fresh weight, dry weight, plant height and the number of leaves of taro and strawberry acclimatized with the acclimatization unit were greater than those of the traditional method at the end of acclimatization, respectively (Figs. 5 and 8).
(3) After being transferred from in vitro to the acclimatization unit or to the control, the fresh weight, dry weight, plant height and the number of leaves decreased (Figs. 5 and 8).
A significant difference in death rate and growth rate of the plantlets between the two methods was shown. Further investigation for the optimum environments for each crop in acclimatization period is needed.

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To research regional difference of frost damage, meteorological observations were made at Hayakita, located in the south-east of the Ishikari-Yuhutsu plain in Hokkaido. Hayakita has crops that are the most easily damaged by frost in the plain. In particular paddy rice plants are damaged by the first frost when their growth is retarded by a cool summer. The first frost in Hayakita occurs 1 week earlier than in other parts of the plain. To research this problem, Chitose that has different topography from Hayakita, was selected as a control area and some meteorological factors such as air temperature, wind speed, solar radiation, net radiation and downward radiation were compared between Hayakita and Chitose. These areas are at the same altitude and share similar surface features. Although Hayakita is surrounded by hills, Chitose is in the center of the plain and is located 12 kilometers away from Hayakita.
In this paper, the daily minimum air temperatures and 4-hour mean values of the meteorological factors in the springs and falls of 1983 and 1984 were compared between Hayakita and Chitose. Also the variations of these factors on clear nights were compared.
Daily minimum air temperatures in both seasons were not significantly different between Hayakita and Chitose. This means that the advection and accumulation of air mass cooled on surrounding slopes are not significant as causes of the frost damage in Hayakita.
The 4-hour mean value of wind speed at Chitose was always greater than that at Hayakita. However, there were no significant differences for the other factors, such as solar radiation, net radiation and downward radiation between Hayakita and Chitose. The air temperature in Hayakita was often lower than that in Chitose, especially in the lower range of temperatures. This tendency was more remarkable in fall than in spring. Sometimes the temperature difference between the two regions reached approximately 5K in fall, accompanied with a large difference of wind speed.
This large difference of air temperature tended to be observed from 20:00 to 4:00 of clear nights. It was caused by temperatures in Chitose often being rapidly increased by raising wind speed during that time, but both temperature and wind speed in Hayakita remained low and unchanged. When comparing temperature profiles to 80 meters above ground level of both regions, it was noted that the stable layer formed by radiative cooling was destroyed from upper portion to near ground surface at Chitose, while, on the other hand, only the upper portion of the layer was destroyed at Hayakita. However, both stable layers remained during the nights when no temperature difference occurred between the regions. Therefore, the occurrence of temperature differences between the regions is due to the difference in the destruction ratio of the stable layer.
The phenomena mentioned above, often appeared in the center of the plain when the upper wind (geostrophic wind) speed and/or direction changed. The upper wind data were obtained from radiosonde data at the 900mb isobaric surface above Sapporo. The changes of wind were classified by following two patterns: i) upper wind speed very small at first, becoming stronger later, and ii) upper wind direction changing from a direction in which WSR (Wind Speed Ratio: the ratio of surface wind speed to upper wind speed at a direction) is small to other one in which WSR is greater. Greater WSR means greater wind speed at ground level for a given upper wind speed; WSR is influenced by surrounding geographic features. Therefore, the WSR values at the center of the plain, lying between the high mountains to the east and west, were large for the north-south direction and small for the east-west direction. On the other hand, WSR values were relatively small for all directions in Hayakita. Thus wind speed in Hayakita was always smaller than that in the center of the plain.
It can thus be recognized that low temperatures conti

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In this paper, the simulation model for microclimatic environment in a rice field described in a previous paper (Inoue, 1985) was improved to extend its applicability. Improved conversational model allowed a variety of output products such as graphic display and line printer of simulated results. The simulation of microclimatic environment by this improved model was made using the observation data of microclimate during the period July 27 to August 31 in 1986. The results obtained by simulation of microclimatic environment in a rice field were compared with the measurements. The results obtained in this paper can be summarized as follows:
(1) An on-line data acquisition and microclimate simulation system (see Fig. 1) was developed for acquisition and analysis of observation data of microclimate, and for simulation of microclimatic environment using the improved model (see Fig. 2). The transmission of data from a data logger in an experimental field to a mini-computer in a laboratory was made through an optical fiber. This system also enabled us to study evapotranspiration and heat balance of the rice field.
(2) Figure 4 shows the diurnal changes in microclimatic environment of the rice field simulated by the model using the external input data as shown in the bottom of this figure 4(D). The diurnal changes in water temperature under the rice canopy and evapotranspiration rate simulated by the model agreed well with those measured at the experimental field with acceptable error (see Fig. 4).
(3) The simulation model was used to examine effects of deep flooding water on the temperature environment in the rice canopy. Simulation results showed that the deep flooding water can protect young rice panicles before the heading time from low air temperature (Fig. 5).
(4) This simulation model was used to predict the change in daily means of microclimatic environment in the rice field, which are needed to predict dynamics of crop growth and fertility elements (Fig. 6). The model was also used to make clear the microclimate characteristics for the dew formation on rice leaves during night time. Simulation results showed that dew occurred on the rice leaves in the canopy under conditions that the leaf temperature falls below the dew point in the surrounding air (see Fig. 7).
The above results showed that the improved simulation model and the developed system for acquisition and analysis of data of rice microclimate could be applied to predict the microclimatic environment in a rice field on line.

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In order to obtain the method to predict the developmental stage of soybean crop, relationships among a developmental rate, daylength and daily mean air temperature were investigated during the period from seeding to flowering. Three plots with respective daylength of 13.3, 14.3 and 15.3 hours were set under field conditions. In each plot 6 cultivars of soybean were seeded on 6 different dates (from May 10 to July 19 with 2-week intervals in 1985). Results obtained were as follows.
(1) The mean developmental rate from seeding to flowering was linearly related to air temperature for each cultivar of each controlled daylength level. Linear regression equations for the relationships between the developmental rate and air temperature were obtained for 6 cultivars and shown in Table 1.
(2) The regression lines shifted with the decrease of daylength, and consequently revealed the increase of the developmental rate (Fig. 2). The differences in their slopes were very little among the cultivars and/or the daylengths examined. The differences in a seeding-to-flowering period among cultivars were analysed in terms of the changes in regression lines, and we confirmed that they were due to difference in sensitivity to daylength.
(3) Our results show that the developmental rate method proposed here predict accurately the flowering stage of soybean crop (Fig. 3).
(4) Within a limited region and season, where the close correlation between daylength and daily mean air temperature is observed, the developmental rate of soybean can be calculated as a unique function of temperature. However, this simplified method, hitherto used, should not be applied to the case out of the range of the observed data.

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