Greenhouse Environmental Conditions Research Articles

Research on Multi-Step Fruit Color Prediction Model of Tomato in Solar Greenhouse Based on Time Series Data

Color change is the most obvious characteristic of the tomato ripening stage and an important indicator of the tomato ripening condition, which directly affects the commodity value of tomato. To visualize the color change of tomato fruit during the mature stage, this paper proposes a gated recurrent unit network with an encoder–decoder structure. This structure dynamically simulates the growth and development of tomatoes using time-dependent lines, incorporating real-time information such as tomato color and shape. Firstly, the .json file was converted into a mask.png file, the tomato mask was extracted, and the tomato was separated from the complex background environment, thus successfully constructing the tomato growth and development dataset. The experimental results showed that for the gated recurrent unit network with the encoder–decoder structure proposed, when the hidden layer number was 1 and hidden layer number was 512, a high consistency and similarity between the model predicted image sequence and the actual growth and development image sequence was realized, and the structural similarity index measure was 0.746. It was proved that when the average temperature was 24.93 °C, the average soil temperature was 24.06 °C, and the average light intensity was 11.26 Klux, the environment was the most suitable for tomato growth. The environmental data-driven tomato growth model was constructed to explore the growth status of tomato under different environmental conditions, and thus, to understand the growth status of tomato in time. This study provides a theoretical foundation for determining the optimal greenhouse environmental conditions to achieve tomato maturity and it offers recommendations for investigating the growth cycle of tomatoes, as well as technical assistance for standardized cultivation in solar greenhouses.

Solar irradiance prediction with variable time lengths and multi-parameters in full climate conditions based on photovoltaic greenhouse

Photovoltaic power generation can provide energy for greenhouses and achieve high quality and high yield of crops. In reality, solar irradiance is fluctuating and intermittent. Thus, the key to ensure efficient photovoltaic power use under greenhouse environmental conditions is to provide an accurate prediction of solar irradiance. Yet, currently studies on irradiance prediction in terms of the variable time lengths, multi-parameter and full climate conditions are rather limited. To improve the comprehensive performance of the prediction model, this paper proposes models of irradiance time series prediction such as Pyraformer, Informer, Transformer and TimesNet. Those models were tested based on the synergistic combination of weather conditions (WC), sunshine time accumulation (STA/h), instantaneous total irradiance (ITI/(W/m2)) and irradiance daily accumulation (IDA/(MJ/m2)). The model performance was rigorously evaluated with 9 prediction lengths, 5 training days, 4 seasons and 5 days for 9 weather conditions. The results showed that the Transformer model had the best overall prediction performance for STA, ITI, IDA and WC at different time steps of 10 min to 24 h. All models were suitable for predicting time series within 1 h. However, TimesNet model was not suitable for predicting time series with steps outside 1 h. On the other hand, by using the sun combination dataset, the Transformer model had the best performance at a time step of 10 min. The mean absolute error (MAE), mean-square error (MSE), root mean squared error (RMSE) and coefficient of determination (R2) of ITI were 0.118 W/m2, 0.059 W/m2, 0.243 W/m2 and 93.9 %, respectively. When exploring the minimum dataset, with the increase of data samples, the prediction effect of TimesNet showed an increasing trend. While, Transformer had the best prediction effect for the dataset with one year of use. When exploring seasonality, Pyraformer model had the best prediction effect on winter and summer, and TimesNet had the best prediction effect on autumn and spring. Local prediction of 9 climate conditions showed that the effects of snow and dust storm were not ideal. The research results showed that the characterization factors that were closely linked to irradiance. The prediction scheme proposed in this paper combined the advantages of different time steps, different factor combination datasets, different data volumes and seasonality, which greatly improves the generalization ability of the model. This study can provide a reference for irradiance prediction and more refined management of photovoltaic (PV) greenhouse.

Internet of Things (IoT)-Driven on Evaporative Cooling System for Tropical Greenhouse Environmental Control

The impact of climate change on tropical agriculture can be mitigated by using controlled environmental conditions in tropical greenhouse buildings with evaporative cooling. Precision agriculture can be applied by adopting technology based on the Internet of Things (IoT) with easy access and real-time monitoring. A study has been conducted to design and manufacture an IoT-based evaporative cooling control system for cultivating horticultural crops in tropical greenhouses. The system consists of an environmental monitoring node and an air cooler actuator control node. Data temperature, relative humidity, and the response of the control actuator can be monitored in real-time via a cloud server. The study also discusses Vapor Pressure Deficit (VPD) as an important factor that needs to be considered in controlling greenhouse environmental conditions. The study used a linear regression test, validation test, analysis of VPD, calculation of the accuracy of the evaporative cooler, as well as evaluation of packet loss.

Drought effects on water status, plant hydraulics and growth in Eucalyptus grandis and clonal hybrids with red gums and E. urophylla

Afforestation with Eucalyptus species occupies over a million hectares in Uruguay, and E. grandis is one of the most cultivated species, mainly for the timber industry. However, the increasing frequency of drought and heat waves in the region raises the need to evaluate hybrids with red gums (E. camaldulensis and E. tereticornis), since they are known to sustain gas exchange and growth even under severe drought conditions. Hybrids with E. urophylla are also evaluated for plantations in subtropical regions. This study aimed to compare the effects of drought on plant water status, hydraulics, and growth of E. grandis (one clone; G), E. grandis × camaldulensis (one clone; GC), E. grandis × tereticornis (one clone; GT), and E. grandis × urophylla (two clones; GU1 and GU2). Two drought-stress cycles were applied to six-month rooted cuttings from mid-spring to early fall under greenhouse environmental conditions. Predawn leaf water potential (?pd), midday leaf water potential (?md), relative leaf water content (RWC), stomatal conductance (gs), and plant growth were measured across each cycle. Daily fluctuation of Ψ was calculated as ΔΨ = Ψpd - Ψmd. Specific (kS) and leaf-specific (kL) hydraulic conductivities and specific leaf area (SLA) were measured at the end of the experiment. Percentage loss of hydraulic conductivity (PLC) was calculated after removing the xylem embolism. Preliminary results suggest that both red-gum hybrids had higher PLC under moderate-to-severe drought, as a consequence of maintaining high water potential gradients to sustain transpiration and carbon fixation throughout the experiment. Under the well-watered condition, no clonal difference was observed. Also, GT showed a three-fold increase in cavitation and had 1.5 times stomatal opening (gs) than the most drought-sensitive clone (E. grandis, G), and exhibited the lowest reduction (17%) in diameter growth under drought. Also, GC attained the highest height at the end of the study, 40% higher than E. grandis, and increased by 25% the SLA under drought. GU clones reached the highest diameter at the end of the study. Correlations among functional variables are explored, and the water supply capacity to the foliage among clones is discussed for a better understanding of drought resistance strategies and growth performance of the different taxa.

Investigation of Dielectric Measurement Model for Coconut Fiber Water Content and the Associated Factors

Coconut fiber has excellent permeability and water retention properties, making it a popular choice as an organic substrate for cultivation in the field of facility agriculture. To investigate the dielectric properties of coconut fiber and develop an accurate measurement model for dielectric water content, a vector network analyzer was used to measure the relative dielectric permittivity of coconut fiber and study the dielectric properties of coconut fiber under different volumetric water contents, temperatures, and salinities. The results indicated that the relative dielectric permittivity of the coconut fiber increased with increasing volumetric water content. The optimal frequency range for measuring the water content of the coconut fiber was 200 MHz–3 GHz, with an optimal frequency of 210 MHz. The dielectric measurement model for the water content in the coconut fiber established at this frequency demonstrated good applicability, with an R2 of 0.9704 and RMSE of 0.0453 cm3/cm3. At the same moisture level (θV of approximately 30% and 50%), the error in the real part of the dielectric permittivity was less than 1.35 between 15 and 35 °C, and the error in the moisture content was less than 0.0339 cm3/cm3. The error due to the salinity was 0.0750 cm3/cm3. The experimental results showed that the modeling of the water content measurement of coconut fiber at 210 MHz can be applied to general greenhouse environmental conditions. This study serves as a valuable reference for calibrating the moisture monitoring sensors used in greenhouses for coir cultivation substrates, emphasizing the need for non-destructive, real-time monitoring of moisture content.

Spatial, Temporal, and Vertical Variability of Ambient Environmental Conditions in Chinese Solar Greenhouses during Winter

The monitoring and control of environmental conditions are crucial as they influence crop quality and yield in Chinese solar greenhouses (CSGs). The objectives of this study were to assess the spatial, temporal, and vertical variability of major environmental parameters in CSGs during winter and to provide greenhouse climate/microclimate characteristics in order to facilitate the monitoring and control of greenhouse environmental conditions. A wireless sensor network (WSN) was deployed in two CSGs: one with crops and one without. Sensors were placed at different locations inside and outside the greenhouses, and the air temperature, humidity, CO2 concentration, light intensity, solar radiation, and wind conditions were measured and analyzed. Significant variability in the spatial, temporal, and vertical distribution of environmental factors was observed in both greenhouses. The average minimum and maximum temperatures and humidity inside the CSG with crops were 9.96 °C (4:00 h) and 24.5 °C (12:00 h), and 32.6% (12:00 h) and 92.1% (5:00 h), respectively. The temperature difference was 2.2 °C between layers in the CSG without crops and 1.4 °C between layers in the CSG with crops. The CO2 concentration in the different layers inside the CSG with crops was highest at night. The average maximum light intensity inside the CSG with crops was 32,660.19 lx, 36,618.12 lx, and 40,660.48 lx (12:00 h to 13:00 h) in the bottom, middle, and top layers, respectively. Sensor positioning in the greenhouse was evaluated by considering the sensors’ data variability. The findings of this study could aid in the development of a better monitoring and control system for CSG’s microclimate during winter. More research is needed on greenhouse microclimate control systems based on this variability analysis, which could improve crop quality and yield in greenhouses.

A hydroponic greenhouse fuzzy control system: design, development and optimization using the genetic algorithm

Aim of study: The design and development of a hydroponic greenhouse fuzzy control system. Area of study: The evaluation was performed using experimental data obtained from the literature. The construction and evaluation of the fuzzy control hydroponic greenhouse system was carried out in a greenhouse in Tehran, Iran. Material and methods: The greenhouse environmental conditions, including temperature, humidity, and carbon dioxide, were controlled. The design of a fuzzy controller begun with the selection of linguistic variables, process status, and input and output variables. The fuzzy control system consisted of three modules: 1) fuzzy module, 2) cost function, and 3) genetic algorithm for the adjustment of the greenhouse environmental conditions.The next step was to select a set of linguistic rules and the type of fuzzy inference process. The rules were set once, and the fuzzy set and output value needed to be specified after the inference, along with the development of a non-fuzzy strategy. Main results: The mean temperatures provided by the fuzzy control system during the day and night were 34.25°C and 23.22°C, respectively, which were improved to 31.17°C and 21.96°C after optimization. The mean humidity was 39.4% and 56.5% during the day and the night, respectively, which turned 60.22% and 74.59% after optimization. The control system also achieved desirable conditions in terms of CO2 amount. Research highlights: The results showed that the measured values of temperature and relative humidity of the greenhouse were improved after optimization with genetic algorithm.

Dehumidification requirement modelling and control strategy for greenhouses in cold regions

Plant transpiration and evaporation from soil surface or growth media in greenhouses produce a large amount of moisture. High relative humidity (RH) favors fungus growth and causes plant diseases thus dehumidification is essential in greenhouses. In this study, a novel model (DehumReq) is developed to predict the dehumidification requirement of greenhouses. The model is based on the crop characteristics, greenhouse environment, and outdoor weather conditions. The year-round predictions give the variation of hourly dehumidification requirement and identify the dehumidifier capacity required for RH control. The model output is validated by the actual dehumidification requirement of a tomato greenhouse. A good agreement is obtained with the coefficient of determination (R2) values up to 0.89 and root mean square error (RMSE) values of less than 10% of maximum dehumidification load between the predictions and measured values. The dehumidification load strategy is also developed using the model, which recommends use 90% of assurance rate for RH control (for setpoint 70, 75, and 80% RH) to keep the load at a reasonable level without causing long high RH period to affect the crops; whereas 100% assurance rate would triple the loads. Using this model and strategy, the greenhouse growers can predict the dehumidification needs and select suitable dehumidifiers. Due to the high loads, it is recommended that in cold region, ventilation using exhaust fan or heat/energy exchangers may provide most of the humidity control while refrigeration or hygroscopic dehumidifiers will supplement when ambient air is humid (summer or mild seasons) or heating cost is a concern (winter season). It is also recommended that the greenhouse ventilation and dehumidification systems should have a temperature-relative humidity (T-RH) control strategy to provide effective and economic T-RH control.

IAA production by Pseudomonas putida associated with rhizosphere of some medicine plants

The present study was carried out in the green house / department of Environmental science / college of Energy and Environment Science, Al-Karkh University of Science, Baghdad. During 2019-2020 under natural environmental conditions in greenhouse. The aim of this study was to evaluate the activity of the rhizosphere soil of two medicine plants including, Watercress (Eruca sativa) and parsley (Petroselinum crispum) plants, to evaluate the effectiveness of the soil surrounding the roots of the tested plants in stimulating rooting growth. Red hibiscus, Alternanthera purple, chrysanthemum, Rosemary and garden mint were planted in rhizosphere soil of the two medicine plants. The results indicated that parsley rhizosphere soil gave the highest values in rooting and seeds germination for the test plants than the Watercress, the results indicated the presence of pseudomonas putida and IAA hormone in the roots rhizosphere soil of the tested plants.

Development of a transpiration model for precise tomato (Solanum lycopersicum L.) irrigation control under various environmental conditions in greenhouse

Transpiration can directly reflect the response of the crop growth and development, therefore irrigation design based on a transpiration model is an important factor towards establishing an efficient irrigation strategy. Thus, the purpose of this experiment is to develop and verify a tomato transpiration model by correcting the relationship between the transpiration rate and environmental factors by measuring the actual transpiration rate. The actual crop transpiration rate, which is measured using a load cell, and the weight changes calculated at 10-min intervals, are applied to the development of the transpiration model. The experimental results show that the transpiration rate has no linear relationship with the radiation amount (Rad) or vapor pressure deficit (VPD). The relationship between Rad and VPD with transpiration rate was fitted by the exponential rise to maximum, and gaussian peak curve, respectively. This allowed a transpiration model to be developed by compensating the Rad and VPD based on the existing Penman–Monteith (P-M) equation. The developed transpiration model showed higher regression constant values than the existing one. The developed transpiration model from the experiment can be utilized for precise irrigation control.

Design exploration study of a smart passive window based on NiTi bent actuator

This paper presents a multi-functional (sensing -actuating) greenhouse ventilation window design heated/cooled naturally by convection, to overcome different industry challenges in terms of designing smart applications. This ventilation window design includes a smart C-shaped NiTi actuator and three-pulley system, and all attached to the window. The force generated in the NiTi wire shrinks the C-shaped to open the ventilation window when the environmental temperature increases. When the environmental temperature decreases, the C-Shaped NiTi actuator returns to its initial position and closes the window. This smart actuation allows energy saving due to natural phase transformation induction (i.e. convection) and high force generation compared to the small NiTi wire mass. Using the pulley system is important as well to reduce the load on the NiTi actuator and enhance its long-life time. In this paper, the smart ventilation window actuator design has been disused followed by a simulation study to investigate the NiTi C-shaped element behavior. The simulation results predict the thermomechanical behavior of the NiTi wire at the proposed greenhouse environmental conditions and the force generated in the wire. For future studies, an experimental investigation could be done to prove the simulation results.

Application of a PhotoThermal model for container-grown conifer seedling production

This study applied a total energy approach to model seedling growth for container-grown loblolly pine (Pinus taeda L.). Seedlings were grown in three container stocktypes representing a range of cavity volume and density patterns. These seedlings were grown under both controlled greenhouse and outside compound environmental conditions under well-defined cultural conditions. Models for temperature and light ranges were created from work on the ecophysiological performance and morphological development of loblolly pine to these atmospheric conditions. A PhotoThermal data set was created by generating hourly averages of these two environmental variables during the growing season. Light and temperature data were integrated, each weighted equally, into PhotoThermal hours (PTH) to assess the crop growth response. Loblolly pine seedling growth in both the greenhouse and outside compound was directly related to PTH. Seedling growth was also related to the container type with the largest cavity volume and lowest cavity density having the greatest growth per PTH. Application of the PhotoThermal model is discussed for growing seedlings in an operational program having multiple production steps, delivery dates and nursery locations.

Environmental monitoring and disease detection of plants in smart greenhouse using internet of things

This research implements the idea of automation using Internet of Things (IoT) in a greenhouse environment. The development is focuses on deployment of agicultural greenhouses into small-scale level transforming it into a smart greenhouse. They are to help in monitoring the greenhouse environment conditions, water irrigation management, image collection using installed cameras as well as predicting diseases in the plants on collected leaf datasets. This research focus on development for the purpose of validating a proposed system design and architecture for a suitable IoT based monitoring for environment conditions, managing water irrigation system and a effective method for detecting leaf diseases on the plants inside a greenhouse environment.

Efficient and easy micropropagation of Morus nigra and the influence of natural light on acclimatization

Micropropagation, which employs various plant growth regulators (PGRs) in the culture medium for the induction of multiple shoots as well as adventitious roots, is a widely-used technique for the propagation of the genus Morus. The main objective of the present study was to evaluate the effect of PGR-free culture medium on the quantitative and qualitative characteristics of the micropropagation of Morus nigra under the growth room and greenhouse environmental conditions. Although a higher rate of multiplication (4.7-5.2 shoots/explant) was obtained from the treatments using Benzyladenine (BA) as the PGR, the PGR-free culture medium also exhibited comparable multiplication rate (4.1 shoots/explant) with a higher quality of shoots and without any symptoms of hyperhydricity. Furthermore, the use of PGR-free culture of M. nigra for in vitro propagation combined the steps of shoot multiplication and rooting phase using the same culture medium, further simplifying the process. In this study, the micro-shoots were also assessed for their in-vitro rooting and acclimatization potential. The incubation of an in-vitro culture of nodal explants in a controlled growth room for 28 days exhibited optimum response with about 90% rooting and 100% plantlet survival during the acclimatization phase. These results were better than those incubated under greenhouse conditions.

Efecto de la orientación y forma de contenedor sobre el crecimiento y desarrollo de chile ancho cultivado en invernadero

En este trabajo se analizó el efecto de la radiación solar sobre condiciones medio ambientales de invernadero y efecto sobre el sustrato colocado en contenedores de manera vertical y horizontal para cultivo de chile ancho. Se encontró qué durante los meses del 26 de agosto al 17 de octubre, hay una radiación solar entre 246.91 (9:00 h) a 642 (12:00 h) W m-2. Lo anterior, indujo al interior del invernadero un contenido diferencial de CO2 a las 9:00 h (853 ppm). En crecimiento y rendimiento de la planta de chile, las plantas cultivadas en contendores horizontales sobresalieron la altura (98.88 cm) y en pesos seco (34.08 g) por planta. Los contenedores horizontales mostraron una mayor correlación entre las variables de peso fresco de raíz y volumen de 99%, mientras que la menor fue entre área foliar y rendimiento. Por lo anterior, concluimos que en cultivo de chile en invernadero se recomienda utilizar contenedores horizontales cara orientación hacia el sur para hacer eficiente su rendimiento en al menos 25 % adicional.

Effect of Nano-Zirconium Oxide and Other Applications on Cowpea Seedlings Growth Under T Salt Stress

This study was carried out in the botanical garden / department of biology /college of science in Mustansiriyah University, Baghdad. During spring 2017 under controlled environmental conditions in greenhouse to study the role of Nano ZrO 2 activity in decrease negative effect of salinity under two levels from NaCl . The treatments included (Salinity levels : natural soil , 3000 ppm and 6000 ppm NaCl) and ( Applications : control , 100 , 300 Zirconium oxide , 5 ppm of liquorice root extract and 10 ppm liquorice root extract and 300 ppm GA3) , The collected data were analyzed statistically using factorial completely randomized design. The results appeared that 300 ppm nano zirconium gave the highest values in all morphological traits (except leaves number) than other treatments. In addition to the highest values in fresh weight, dry weight, Chlorophyll a, Chlorophyll b and carbohydrate contain. Also 300 ppm nano zrconium oxide reduced the effect of salinity stress (3000 and 6000 ppm NaCl) by giving the highest values in morphological traits and in chemical contains (chlorophyll and carbohydrate) in Cowpea seedling growth.

Forest and grassland cover types reduce net greenhouse gas emissions from agricultural soils

Western Canada's prairie region is extensively cultivated for agricultural production, which is a large source of greenhouse gas emissions. Agroforestry systems are common land uses across Canada, which integrate trees into the agricultural landscape and could play a substantial role in sequestering carbon and mitigating increases in atmospheric GHG concentrations. We measured soil CO2, CH4 and N2O fluxes and the global warming potential of microbe-mediated net greenhouse gas emissions (GWPm) in forest and herbland (areas without trees) soils of three agroforestry systems (hedgerow, shelterbelt and silvopasture) over two growing seasons (May through September in 2013 and 2014). We measured greenhouse gas fluxes and environmental conditions at 36 agroforestry sites (12 sites for each system) located along a south-north oriented soil/climate gradient of increasing moisture availability in central Alberta, Canada. The temperature sensitivity of soil CO2 emissions was greater in herbland (4.4) than in forest (3.1), but was not different among agroforestry systems. Over the two seasons, forest soils had 3.4% greater CO2 emission, 36% higher CH4 uptake, and 66% lower N2O emission than adjacent herbland soils. Combining the CO2 equivalents of soil CH4 and N2O fluxes with the CO2 emitted via heterotrophic (microbial) respiration, forest soils had a smaller GWPm than herbland soils (68 and 89kgCO2ha−1, respectively). While emissions of total CO2 were silvopasture>hedgerow>shelterbelt, soils under silvopasture had 5% lower heterotrophic respiration, 15% greater CH4 uptake, and 44% lower N2O emission as compared with the other two agroforestry systems. Overall, the GWPm of greenhouse gas emissions was greater in hedgerow (88) and shelterbelt (85) than in the silvopasture system (76kgCO2ha−1). High GWPm in the hedgerow and shelterbelt systems reflects the greater contribution from the monoculture annual crops within these systems. Opportunities exist for reducing soil greenhouse gas emissions and mitigating climate change by promoting the establishment of perennial vegetation in the agricultural landscape.

Efficacy of spray applications of entomopathogenic fungi against western flower thrips infesting greenhouse impatiens under variable moisture conditions

Laboratory bioassays of three entomopathogenic fungi (Beauveria bassiana strain GHA, Metarhizium brunneum strain F52, and Metarhizium anisopliae s.l. strain ESC-1) were conducted against 2nd-instar nymphs of Frankliniella occidentalis. All three fungi were highly virulent, with respective LC50s of 193, 140, and 72conidia/mm2 of treated leaf surface. Efficacy tests were conducted against thrips infesting small plots of Impatiens walleriana on open greenhouse benches under variable moisture conditions. Multiple spray applications of fungal conidia suspended in 0.01% Silwet® were made at a high rate of 2×1014conidia/ha at 3–5-day intervals, and efficacy was assessed from twice-weekly samples of both flowers and foliage. During tests, moisture conditions were modified via controlled sprays of water onto the concrete floor beneath the greenhouse benches for a period of ca. 40h (from the evening through the second night) following each application (post-spray period). Efficacy of the pathogens expressed as percent reduction of the combined populations of thrips nymphs and adults relative to spray-carrier controls was ultimately correlated to greenhouse environmental conditions. Mean relative humidity (RH) over all test days was a strong predictor of thrips control on foliage (R2=0.820) and flowers (R2=0.756). Fungal efficacy was most strongly and consistently predicted by moisture conditions during the post-spray periods. The single best predictor was mean number of hours during post-spray periods when RH was ⩾80% (R2 foliage=0.834; R2 flowers=0.908). The three fungi produced similar levels of thrips control under comparable moisture conditions. Maintenance of 80% RH for ca. 25h during post-spray periods resulted in >70% control of thrips in foliage. Substantially longer periods of high humidity (35h) were required to achieve comparable control in flowers. Control⩾70% in both foliage and flowers prevented pest populations from increasing. Aspects of the impatiens crop that create a challenge for thrips control using fungal entomopathogens are described and discussed.

Design, implementation and evalution of a central unit for controlling climatic conditions in the greenhouse

In greenhouse culture, in addition to increasing the quantity and quality of crop production in comparison with traditional methods, the agricultural inputs are saved, too. Recently, using new methods, designs and materials, and higher automation in greenhouses, better management has become possible for enhancing yield and improving the quality of greenhouse crops. The constructed and evaluated central controller unit (CCU) is a central controller system and computerized monitoring unit for greenhouse application. Several sensors, one CCU, several operators, and a datacollection and recorder unit were the major components of this system. The operators included heating, cooling, spraying, ventilation and lighting systems, and the sensors are for temperature, humidity, carbon dioxide, oxygen and light in inside and outside the greenhouse. Environmental conditions were measured by the accurate sensors and transmitted to the CCU. Based on this information, the CCU changed variables to optimize the greenhouse environmental conditions to predetermined ranges. This system was totally made of local instruments and parts and had the ability to integrate with the needs of the client. The designed and implemented CCU was tested in a greenhouse located in Agriculture and Natural Resources Research Center of Khuzestan Province during summer season of 2011. The CCU was operated successfully for controlling greenhouse temperature in the range of 22-29 C, relative humidity of 35-55%, artificial lighting in the case of receiving radiation of less than 800 Lux and turning on the ventilation units if the concentration of carbon dioxide was more than 800 mg/L.

Aspects of the epidemiology and control of powdery mildew (Oidium neolycopersici) on tomato in Ontario, Canada

The epidemiology and control of powdery mildew (Oidium neolycopersici) of tomato (Solanum lycopersicum L.) was studied in greenhouse, growth chamber, and field experiments at Harrow, Ontario. Greenhouse environmental conditions were more favourable for disease development, with higher disease progress rates than in the field. Symptoms were more severe on older, lower leaves where the air temperature was slightly lower and relative humidity higher than on young leaves at the top of the canopy. A temperature of 22°C with 16 or 24 h of leaf wetness was optimal for disease development in a growth chamber experiment. Early inoculation resulted in significantly greater final disease severity and area under the disease progress curve than later inoculations. Disease progress in greenhouse and growth chamber trials was best described by the Gompertz model, while the logistic model was best for disease progress in field studies and for sections of plants in greenhouse studies. No yield loss occurred in field studies. The best disease control was obtained with acibenzolar-S-methyl (Actigard®), trifloxystrobin (Flint®), JMS-Stylet Oil®, azoxystrobin (Quadris®) and sulphur applied as protectants. Some phytotoxicity occurred with Actigard in greenhouse studies. Serenade® (Bacillus subtilis) was less effective while Kaligreen, Sporodex® (Pseudozyma flocculosa), copper octanoate and fumed silica were ineffective. Quinoxyfen was phytotoxic at the rate applied. Several tobacco cultivars, jimsonweed, American and black nightshade were susceptible to infection by O. neolycopersici. Eggplant, hairy nightshade and bittersweet were less susceptible, while no visible symptoms developed on pepper, potato and tomato ‘Grace’, and only trace levels of sporulation occurred on cucumber.