In Site Net Photosynthesis Measurement of a Plant Canopy in a Single-Span Greenhouse

Takakura, T.; Sunagawa, Haruki; Tamaki, Maro; Usui, Takae; Taniai, Naoki

doi:10.24297/jaa.v7i2.6092

Cited by 6 publications

(10 citation statements)

References 4 publications

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“…It has been demonstrated that using the energy balance equation itself, which is the basis of the Penman-Monteith Equation, is a simpler approach [29] .…”

Section: Evapotranspiration Sensormentioning

confidence: 99%

“…However, the data obtained for the canopy photosynthesis were scattered because of frequent changes in the ventilation amount. It is presented in Figure 15 that although the main factor affecting net photosynthesis is net solar radiation, other factors such as air temperature, CO 2 concentration, and humidity cannot be neglected [29] .…”

Section: Photosynthesis and Transpiration Measurementmentioning

confidence: 99%

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Research exploring greenhouse environment control over the last 50 years

Takakura

2019

International Journal of Agricultural and Biological Engineering

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Environments do not exist in isolation. Their main components in greenhouse systems are plants. Without consideration of plants, analysis of greenhouse environments and environmental control of greenhouses can be accomplished, although it is not simple to achieve. Initial attempts were undertaken to analyze greenhouse environments and then reproduce them. Ventilation rate effects on plant photosynthesis in a growth chamber were reported in 1966. Computer simulations then became a main subject of research. The first dynamic computer simulation of a greenhouse environment including plants was published in 1971. According to innovations of computer technology, the use of minicomputers and microcomputers spread in many areas. By measuring the net photosynthesis of lettuce plants grown under artificial lighting, air temperature was optimized using a minicomputer with the hill-climbing method. The method was designated as the Speaking Plant Approach to environment control (SPA). After the author developed the first reported environmental control system in Japan, systems using microcomputers spread widely for greenhouse environmental control. Knowledge-based expert systems were tested for plant management. Also, a machine vision system was developed to detect critical moments for watering of muskmelon plants. The first feed-forward control method for greenhouses with a large heat mass was reported. Then space farming was tested in 1996 to assess gravity effects on plants. Energy-saving aspects such as solar sterilization, ground heat storage system, and storage using phase change material (PCM) have been reported. Defects of ordinary solarimeters were reported in 2008 along with an approach to estimate evapotranspiration in a greenhouse without the effect of so-called cosine law. Later, this technique was expanded to estimate photosynthesis of the plant canopy in a greenhouse using newly developed sensor units.

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“…It has been demonstrated that using the energy balance equation itself, which is the basis of the Penman-Monteith Equation, is a simpler approach [29] .…”

Section: Evapotranspiration Sensormentioning

confidence: 99%

Section: Photosynthesis and Transpiration Measurementmentioning

confidence: 99%

Research exploring greenhouse environment control over the last 50 years

Takakura

2019

International Journal of Agricultural and Biological Engineering

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“…They determined the ventilation rate using N2O tracer gas under leakage and a small window aperture (therefore a low ventilation rate). Furthermore, Takakura et al (2017) calculated the canopy photosynthesis based on the CO2 balance and the ventilation rate using the energy balance technique under a high ventilation rate condition. Dieleman et al (2017) conducted plant monitoring based on crop measurement techniques using the Crop Photosynthesis Monitor (for measuring crop photosynthesis) and the CropObserver (for measuring photosynthetically active radiation and fluorescence of a large area of the crop).…”

Section: Measurement Of Photosynthetic Rate In a Greenhousementioning

confidence: 99%

“…Monitoring is required to determine whether the greenhouse climate is suitable to the needs of the crop. Real-time monitoring of net photosynthesis of a plant canopy in a greenhouse is crucial to elucidate and improve plant environments (Takakura et al, 2017). Leaf photosynthesis is measured by determining the CO2 uptake of a leaf using a portable gas exchanger device (Hao et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

The Essential Factor of Ventilation Rate in Prediction of Photosynthetic Rate Using the CO<sub>2</sub> Balance Method

Tusi

Shimazu

2020

RAS

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Monitoring photosynthesis is a fundamental process to improve the yield and quality of plants in a greenhouse. The CO2 balance method is often employed to predict the photosynthetic rate of plants. We reviewed the essential parameters for predicting photosynthetic rates of plants canopy in greenhouses using the CO2 balance method. Even in a naturally ventilated greenhouse, ventilation rate is an essential parameter for the CO2 balance method, but it must be measured in real time as it fluctuates with weather conditions. We studied three types of ventilation rates (the tracer gas, heat balance, and water vapor balance methods). Comparing the measuring techniques of ventilation rate provided us an understanding of the strengths and weaknesses of each method. This knowledge can guide us to choosing the best method based on accuracy, device usage, practicality, and the installation budget. Most researchers have measured and controlled CO2 concentrations in a greenhouse using an infrared gas analyzer and predicted the ventilation rates using the tracer gas method. This method is suitable for the measurement of low and closed ventilation. The estimated ventilation rate by the heat balance method is recommended for large ventilation openings. The water vapor balance method is sufficient for measuring the ventilation rate when there is a large quantity of water vapor due to plant transpiration. The reliability of this method depends on the accuracy of short-term transpiration measurements. Improved water vapor balance techniques can benefit various greenhouse applications with different ventilator configurations, owing to the flexibility and ease of use compared to those of other methods.

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“…However, CO 2 is not particularly reliable for real-time estimation of N of cropped greenhouses, and N 2 O and SF 6 are too expensive to use in commercial greenhouses. By contrast, H 2 O can be used for real-time estimation of N even though the greenhouse contains plants, provided that evapotranspiration rate therein is accurately measured Takakura et al, 2009Takakura et al, , 2017 Nevertheless, there appears to be room for improving accuracy, especially under the conditions where N suddenly changes Takakura, 2017 . The AD models of natural ventilation are based on Bernoulli's principle. They consider that airflow through a vent is caused by the difference between the pressure inside and outside the vent, and that the pressure difference is induced by buoyancy forces so-called stack effect or thermal effect and wind forces wind effect e.g., Kozai et al, 1980;Sase et al, 1980;Boulard and Baille, 1995;Boulard et al, 1996;Kittas et al, 1997 . Using this method, it is possible to estimate N in real time with measured levels of relevant environmental elements, including the difference between the temperature inside and outside the greenhouse for stack effect and wind speed for wind effect , as well as the opening area of vents.…”

Section: Introductionmentioning

confidence: 99%

Comparison of neural network models with aerodynamic and empirical models toward real-time estimation of the number of air exchanges per hour of a naturally ventilated greenhouse

Matsuda

Hayano

Yagi

et al. 2019

J. Agric. Meteorol.

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The feasibility of estimating the number of air exchanges per hour N of a naturally ventilated greenhouse in real time using neural network NN models was evaluated. An aerodynamic AD model and an empirical model were also used to compare different types of model. The value of N for an eight-span Venlo-type greenhouse with roof vents containing no plants was measured using the tracer gas method with CO 2 for 17 d. An AD model derived from Bernoulli's principle, an empirical model, and several NN models in which explanatory variables differed were trained and validated with 4,508 data points subjected to 10-fold cross-validation. We first compared the AD model, the empirical model, and two NN models that used the same explanatory variables in the empirical model, with and without wind direction. The mean accuracy in terms of root mean square error RMSE and coefficient of determination r 2 in the relationship between measured and estimated N values was the highest for the two NN models, followed by the empirical model and AD model. We next compared four NN models. The differences among them included that, as explanatory variable s , only the difference between inside T i and outside T o air temperatures or both T i and T o was used and whether solar irradiance I was used or not. There was a slight improvement in accuracy when using I, irrespective of how air temperature was handled. The NN models thus tended to exhibit a higher degree of accuracy in estimating N of a naturally ventilated greenhouse than the AD and empirical models considered in this study. For the NN model that performed the best in our comparison, a mean RMSE of 1.08 h 1 and a mean r 2 of 0.79 were observed.

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In Site Net Photosynthesis Measurement of a Plant Canopy in a Single-Span Greenhouse

Cited by 6 publications

References 4 publications

Research exploring greenhouse environment control over the last 50 years

Research exploring greenhouse environment control over the last 50 years

The Essential Factor of Ventilation Rate in Prediction of Photosynthetic Rate Using the CO<sub>2</sub> Balance Method

Comparison of neural network models with aerodynamic and empirical models toward real-time estimation of the number of air exchanges per hour of a naturally ventilated greenhouse

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