The method of existing supplementary light on sunlight-artificial light greenhouse is used by 100% turn on and off control in the case of the light quantity under arbitrary value consequently, there are many cases giving artificial light beyond neccessary value.
The purpose of this investigation is to supply insufficient light quantity with arbitrary quality that is the most suitable and the lowest necessary to obtain the ideal growth of crop after calculating by computer photosyn-thetically active raduation (PAR) and light quantity from changing sun-light according to solar altitude and aerosol.
Artificial lights are used high-pressure sodium lamps and high pressure mercury lamps with light regulator to obtain arbitrary quality R/B ratio especially.
On this experiment, the light intensity and quality are set 220-240ηmol/m²/s (PPFD), R/B ratio≅3 respectively.
Electric charges using this method are economized 46% comparing with the usual method at the autumnal hydroponics of Brassica rapa L. 'Komatsuna' (Nov. 27th-Dec. 25th).

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In the intentional production of crops in a plant factory, it is necessary to measure the progress of growth of an individual plant. There is a significant positive correlation between several growth indices obtained by image processing and the top fresh weight of lettuce plants (Lactuca sativa L. non-heading type) grown in a plant factory. The horizontal projected leaf area for several days after sowing made it possible to estimate the top fresh weight. Therefore, we have developed an automatic plant growth monitoring system for vegetables grown in a plant factory. This system is organized into five parts, CCD camera with a transfer mechanism, a personal computer for image processing CPU, a image memory unit, a TV monitor and a printer. To evaluate the growth of transplants individually, we have developed growth prediction function with fuzzy inference.
Using this function, the growth of lettuce plants grown in a plant factory was estimated continuously and automatically by use of a low-cost automatic plant growth monitoring system with a personal computer.

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A low-cost simple seeding machine which is automated and possessed of minimum function is developed. According to the results of performance tests, it can exactly seed a grain at urethane mat to be used in water culture by fixed deep.

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Occurrence of blossom-end rot of tomato fruits is serious problem in tomato cultivation in greenhouses and is considered to be caused by lack of calcium. In order to prevent occurrence of blossom-end rot, effect of air flow to fruits was tested and the mechanism of prevention of occurrence of blossom-end rot was analysed.
Data were collected in the experiment of zone cooling with cold water or fog, the results of which were reported in previous paper (Cho et al., SHITA JOURNAL, 4 (1) : 30-39, 1992). Average relative humidity in cold water cooling was 67-68% and that in fog cooling was 75-76%. Tomato plants (Lycopersicum esculentum MILL. cv. House momotaro) were cultivated in hydroponics with nutrient solution of EC of 0.4 S-m^-1.
The results were as follows.
(1) Percentages of occurrence of blossom-end rot of tomato fruits in cold water cooling with air flow to fruits, in cold water cooling, in fog cooling with air flow to fruits and in fog cooling were 0%, 4%, 0% and 55%, respectively. Air flow to fruits was effective for prevention of occurrence of blossom-end rot.
(2) Solar radiation, water uptake rate and calcium uptake rate showed similar changes (Fig. 1 and Fig. 2), indicating that calcium movement follows water movement in tomato plants. Fig. 2-A indicates that occurrence of blossom-end rot in this experiment was not due to decrease in calcium uptake from nutrient solution.
(3) Air flow to fruits was effective for increasing distribution ratio rather than concentration of calcium in dry matter of fruits (Table 1 and Table 2).
(4) Blossom-end rot occurred about 8-12 days after anthesis, when diameter growth rate of fruits was fastest (Fig. 4).
(5) Occurrence of blossom-end rot was affected by humidity. High humidity leads to decrease in transpiration of tomato plants, which would result in occurrence of blossom-end rot. The mechanism of the effect of air flow to fruits is considered that air flow to fruits promotes transpiration from fruit surface and inflow of water and calcium into fruits.

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We have studied the intentional production and quality control of lettuce plants (Lactuca sativa L. non-heading type) grown in a plant factory. Using the growth indices obtained by image processing especially leaf area, it is possible to measure the growth of a lot of individual plants continuously. The distribution of the growth was represented by frequency function, therefore, it is possible to evaluate the production by the quality control technique in the industrial fields. Furthermore, there was a significant relationship between the growth rate by the regression curve of horizontal projected leaf area and the yield. With the advancement of micro-computer technology, we can use a low cost image processing system with a personal computer.
In conclusion, the horizontal projected leaf area of lettuce transplants for several days after sowing made it possible to estimate the yield and control the production.

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It is desirable to develop an agricultural robot for reduction of labor and sterile cultivation in greenhouse or plant factory recently. It was already reported that basic mechanism of manipulator to work in tomato plant field was studied. The manipulator has 7 degrees of freedom involving prismatic joints.
In this paper, the manipulator was manufactured as a trial and a control method for the redundant manipulator was investigated on purpose to harvest tomato fruit. The method is as follows; operational space was segmented into 50×75 mm small region at first. Secondly, joint angles were calculated for each segmentation by use of evaluating function which contains measure of manipulatability, manipulator and straight moving distance, and displacement of vertical prismatic joint as parameters. Thirdly, the joint angles were referred before manipulator moving.
Harvesting experiment was done using the control method, after a hand with absorptive pad was attached to the manipulator. From the results, the following was obtained.
(1) Segmentation of operational space made control of redundant manipulator easy and speedy.
(2) It was possible for the manipulator to harvest any objects in configuration whose manipulatability and straight moving distance were big.
(3) Manipulator could harvest with reasonable displacement of vertical prismatic joint by using of evaluating function which contains the displacement as parameter.

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