Archive - Abstract

Vol.54 No.1 (March, 2023)

  • Notes (Japanese)
  • Development of a Windbreak Attachment for Greenhouses and an Evaluation of its Effectiveness in Reducing Air Leakage
  • Tadashi KUMAZAKI, Yusuke OTSUKI, Masaki NAKANISHI, Shinichi MIURA
  • Air leakage reduces the effectiveness of CO2 enrichment in unventilated greenhouses. In this study, a windbreak that can be directly attached to an existing greenhouse was developed to reduce the air leakage; the windbreak was termed a ‘windbreak attachment’. The specifications of the windbreak attachments were examined for two small greenhouses. Pipes were erected at 0.4 m away from the wall of each greenhouse and connected to the eaves of the respective greenhouses with fastening apparatus to form overhangs. The sides of the overhangs were covered with plastic nets, which were used as the windbreak attachments. The windbreak attachments were applied to the sides of the greenhouses for some tests while leaving the ends without windbreaks, and to both the sides and ends of the greenhouses for other tests. The leakage rate was measured in the unventilated greenhouses by the tracer gas technique using CO2 as a tracer gas. The leakage rates of the greenhouses correlated significantly with outside wind velocity, consistent with many previous studies. The air leakage of the greenhouse with windbreak attachments on both the sides and ends was less than that of the greenhouse with windbreak attachments on the sides, as evaluated effectiveness in reducing air leakage using the ratio of the slopes of the regression lines. Therefore, we concluded that windbreak attachments were needed not only on the sides of the greenhouse but also on the ends. The effect of the windbreak attachments on the leakage rate of the greenhouse was also evaluated for a medium-sized greenhouse. As a result, the leakage rate of the greenhouse with windbreak attachments installed on both the sides and ends was reduced to 53.5% of that the same greenhouse without windbreak attachments.

Keywords:Tracer gas method, Air leakage, Ventilation rate

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Vol.54 No.2 (June, 2023)

  • Research Papers (Japanese)
  • Measuring Average Solar Radiation in a Greenhouse
  • Maro TAMAKI, Soma SUGANO, Masahisa ISHII, Sadanori SASE, Tadashi TAKAKURA
  • Average solar radiation must be considered to evaluate the amounts of photosynthesis and growth of plants in a greenhouse. Nevertheless, finding the average solar radiation in a greenhouse is not easy because the light incidence angle and greenhouse frame shadows strongly affect the internal solar radiation the solar radiation amount varies spatially. For this study, three simple methods were used to ascertain the average irradiance in a greenhouse: pyranometer improvement, computer simulation using greenhouse models, and comparison of direct measurements on clear and cloudy days. Results clarified that when the solar transmittance in the greenhouse was measured during cloudy weather, when the greenhouse had no frame shadows, the solar radiation transmittance remained constant even when the solar radiation varied over time. Comparison between clear and cloudy days revealed no difference in transmittance. These findings suggest a method to measure the average solar radiation in a greenhouse. First, using two upward-facing pyranometers, one must be installed outside the greenhouse. The other must be installed inside the greenhouse. Then measurements are taken on cloudy days to obtain the transmittance. Next, the outside pyranometer output must be multiplied by the solar radiation transmittance to obtain average solar radiation in the greenhouse for any time. If necessary, a downward-facing pyranometer should be installed in the greenhouse. Then its measured value must be subtracted from the inside upward-facing pyranometer output to calculate the average amount of solar radiation in the greenhouse.

Keywords:diffuse plastic covering, diffused radiation, pyranometer, solar radiation transmittance

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  • Notes (Japanese)
  • Effect of Hot Water Supply System for Calves using Solar Water Heater
  • Masamichi Sato
  • Improve the growth of livestock (calves) in winter, we developed a hybrid hot water supply system connecting a solar water heater and oil heating, and verified economic effects of hot water supply to calves. Water warming in the solar water heater during the study period was 0.9-37.2 ℃ (average 21.7 ℃). Water which supplied to the livestock drinking water tank from the solar water heater via the heat source for oil heating exceeded 35°C on some days. After that, the water temperature decreased with the passage of time due to heat dissipation. Comparing the market of calves at Kawajiri Farm (Shimonoseki City, Yamaguchi Prefecture), which is a demonstration farm, after the introduction of the hot water supply system, the weight of calves increased compared to before, and the daily gain was over 1.0 kg/head, and the profitability improvement was about 42 000 yen/head (difference in average auction price by each bull). It was suggested that the usefulness of this developed hybrid hot water supply system.

Keywords:calf, hot water supply, solar water heater

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Vol.54 No.3 (September, 2023)

  • Research Papers (Japanese)
  • Effect of Winter Nighttime Downward Longwave Radiation on the Overall Heat Transfer Coefficient of Agricultural Covering Materials
  • Yuta OHASHI, Ryota TSUCHIYA, Masahisa ISHII and Makio HAYASHI
  • The overall heat transfer coefficients of various agricultural covering materials were measured under winter nighttime downward longwave radiation from 212 to 297 W m−2 reproduced in an experimental device. Under the downward longwave radiation conditions of this study, the ranges of overall heat transfer coefficients of glass, polyolefin film, fluorocarbon resin film, polyvinyl chloride film, polyvinyl acetate film, and polyethylene film were 5.2–5.7, 5.5–6.4, 5.6–6.4, 6.0–6.9, 6.7–7.6, and 6.7–7.6 W m−2 ºC−1, respectively. The overall heat transfer coefficient tended to increase as the downward longwave radiation decreased. The relationship between downward longwave radiation and the overall heat transfer coefficient could be approximated for each covering material by a straight line. Therefore, it should be possible to calculate the amount of overall heat transmission of a greenhouse more accurately by considering the downward longwave radiation and applying each material’s respective approximate equation. In addition, it was possible to approximate the absorptance (transmittance) of longwave radiation and the overall heat transfer coefficient in each covering material with a quadratic function. Therefore, it should be possible to estimate the overall heat transfer coefficient of covering materials with unknown heat insulation capacity under different downward longwave radiation by measuring the absorptance or transmittance of longwave radiation.

Keywords:greenhouse, carbon neutral, greenhouse horticulture, decarbonization, heating load, longwave radiation, heat transfer, film, heat retention

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  • Research Papers (Japanese)
  • Characteristics of Composting Reaction for Dairy Cattle Manure Mixed with Biochar -Effects of Mixing Rice Husk Biochar, Bamboo Biochar, and Granular Wood Available in Japan on Nitrous Oxide, Methane, and Ammonia Emissions-
  • Hideki MORIYAMA, Masahisa ISHII, Ryota TSUCHIYA and Yuta OHASHI
  • This study aimed to clarify the characteristics of composting reaction for dairy cattle manure mixed with biochar (rice husk biochar, bamboo biochar, and granular wood) commercially available in Japan. Composting of dairy cattle manure mixed with 10 % biochar (wet weight basis) was performed for 35 days using a lab-scale composting device to analyze compost temperature, microbial activity, and N2O, CH4, and NH3 gas emissions. The results showed that rice husk biochar reduced NH3 emissions by 59.8 % compared to the control, while bamboo charcoal only reduced NH3 emissions by 6.8 %. N2O and CH4 emissions were reduced by all biochar types, with bamboo charcoal showing the highest suppression among them. On the other hand, the biochar treatments showed the same tendency as the control treatment regarding the increase in the maximum temperature in the initial composting stage and the persistence of a high-temperature period above 55 ºC. In addition, no significant differences in cumulative CO2 emissions or organic matter decomposition rates, representing microbial activity, were observed between the biochar treatments and the control. The results indicate that mixing biochar does not affect the composting process. Although the biochar used in the study did not affect the promotion of composting of dairy cattle manure, some types of biochar were effective materials in reducing NH3, N2O, and CH4 emissions.

Keywords:composting, biochar, dairy cattle manure, nitrous oxide, methane, ammonia

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Vol.54 No.4 (December, 2023)

  • Research Papers (Japanese)
  • Estimation of Pronunciation Locations in Multiple Whitefly Released Environment Using a Narrow Spacing Microphone Array
  • Hirotaka Obo，Tadashi Ebihara，Naoto Wakatsuki，Koichi Mizutani
  • Whiteflies are known to have a characteristic ecology in which individuals communicate acoustically with each other by attaching to the dorsal surface of the leaf body and vibrating the leaf with their legs, and the sound or vibration is transmitted to another whiteflies. Recently, it has become clear that this acoustic communication plays an important role in mating behavior. In this paper, we constructed an acoustic sound localization system using a narrow-spacing microphone array (16ch-MA) to observe the acoustic communication of whiteflies on the leaf body. We compared and verified two types of sound source localization methods: Indicator A (TDoA: time difference of arrival) and Indicator B (PDoA: power difference of arrival). The system was designed using a heat map of the indicators, which were used to estimate the pronunciation location. As a result, it was confirmed that the location of whiteflies and the location given by the heat map approximately matched. Acoustic communication and behavior could be ecologically monitored when a single whitefly was on a leaf, when a male and a female were parasitized as one pair, and when a male and a female were parasitized at different positions on the leaf body. We were also able to estimate the positions of pronating whiteflies when 10 whiteflies were released. In the experiment, indicator A (TDoA) tended to be suitable for cucumber leaves, and indicator B (PDoA) for perilla leaves.

Keywords:whitefly, insect acoustic communication, microphone array, sound source localization, acoustic positionin

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Journal

J-STAGE