Controlled Environment Horticulture: Latest Advances and Future Prospects

A special issue of Horticulturae (ISSN 2311-7524). This special issue belongs to the section "Protected Culture".

Deadline for manuscript submissions: closed (31 January 2024) | Viewed by 32025

Special Issue Editors


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Guest Editor
Urban Agriculture & Controlled Environment Agriculture, Department of Agriculture, Veterinary and Rangeland Sciences, University of Nevada, Reno, NV 89030, USA
Interests: indoor vertical farming; hydroponics; aquaponics; LEDs; greenhouse production; phytochemicals

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Guest Editor
Department of Plant Sciences, Institute of Agriculture, University of Tennessee, Knoxville, TN 37996, USA
Interests: greenhouse production; hydroponics; indoor agriculture; phytonutrients

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Guest Editor
School of Integrative Plant Science, 134A Plant Science Bldg, Cornell University, Ithaca, NY 14853, USA
Interests: reducing energy use in CEA; LED lighting; climate control; mineral nutrition; new crops
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Rapid urbanization, increasing population, decreasing resources, and decreasing nutrition security are current global challenges. Controlled environment horticulture (CEH) has the potential to revolutionize our food systems by enhancing nutrition security, increasing local crop production, reducing food mileage, and minimizing resource use. CEH systems, including greenhouses, vertical farms and high tunnels, enable environmental parameters, including temperature, air, light (intensity, quality, and duration), and CO, to be controlled, eliciting desired yield and quality responses in a predictable manner. These systems enable year-round production of fresh food, ornamental, and high-value crops. However, due to rising production costs, the following important areas for production improvement remain: high energy demand, labor (training and automation), improving climate control (using traditional and AI approaches), phytonutrient improvement and sustainability.

The goal of this Special Issue, entitled 'Controlled Environment Horticulture: Latest Advances and Future Prospects', is to highlight cutting-edge innovative research, climate-smart advanced technology, and cultural practices and concepts that could address these challenges and enhance the efficiency and sustainability of controlled environment horticulture.

Dr. Most Tahera Naznin
Dr. Kellie Walters
Prof. Dr. Neil Mattson
Guest Editors

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Keywords

  • automation
  • breeding
  • environmental factors
  • energy efficiency
  • fresh food
  • greenhouse production
  • indoor farming
  • medicinal plants
  • ornamentals
  • phytonutrients

Published Papers (18 papers)

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Research

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13 pages, 3589 KiB  
Article
The Effect of the Daily Light Integral and Spectrum on Mesembryanthemum crystallinum L. in an Indoor Plant Production Environment
by Jun Wei Chen, Kateřina Patloková and Robert Pokluda
Horticulturae 2024, 10(3), 266; https://doi.org/10.3390/horticulturae10030266 - 11 Mar 2024
Viewed by 814
Abstract
The effect of artificial lighting with different light spectra and photoperiods/daily light integrals (DLIs) on the yield, bioactive compounds and antioxidant capacity of the common ice plant (Mesembryanthemum crystallinum) was studied. Four-week-old seedlings were selected and subjected to four different light [...] Read more.
The effect of artificial lighting with different light spectra and photoperiods/daily light integrals (DLIs) on the yield, bioactive compounds and antioxidant capacity of the common ice plant (Mesembryanthemum crystallinum) was studied. Four-week-old seedlings were selected and subjected to four different light spectra made up of different combinations of blue (400–500 nm), green (500–600 nm) and red light (600–700 nm), with a total photosynthetic photon flux density (PPFD) of 180 µmol.m−2.s−1. Concurrently, the effect of the daily light integral (DLI) was also studied, with the light treatment photoperiod set at 18 h and 21 h. Biometric parameters such as fresh mass weight, leaf area, leaf width, and dry mass, together with plant metabolite contents such as total antioxidant capacity (TAC), vitamin C, chlorophyll a and b content, and total carotenoids and nitrates, were investigated. It was found that the plants grew better when exposed to light with a higher proportion of the red and blue spectrum, with the highest fresh mass of 68 g observed at a photoperiod of 18 h. On the other hand, green spectrum light was not found to yield any significant improvement in shoot weight, leaf area, or leaf size. It was also found that dry mass, chlorophyll b and nitrates were not influenced by the light spectrum but were influenced by the photoperiod duration. While both the dry mass and nitrate content increase as the photoperiod increases, a longer photoperiod had a negative effect on chlorophyll a, chlorophyll b and total carotenoids, with their content decreasing by as much 29% for chlorophyll a, 59% for chlorophyll b and 29% for total carotenoids. TAC content was seen to increase by more than 24% under the influence of 66% more green light, and 38% more under the 21 h photoperiod. Full article
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14 pages, 2378 KiB  
Article
The Growth and Tuber Yield of Potatoes (Solanum tuberosum L.) under Varying LED Light Spectrums in Controlled Greenhouse Conditions
by Md Hafizur Rahman, Md. Jahirul Islam, Umma Habiba Mumu, Byeong-Ryeol Ryu, Jung-Dae Lim, Md Obyedul Kalam Azad, Eun Ju Cheong and Young-Seok Lim
Horticulturae 2024, 10(3), 254; https://doi.org/10.3390/horticulturae10030254 - 7 Mar 2024
Viewed by 1098
Abstract
Plant growing using light-emitting diodes (LEDs) in a controlled environment is a revolutionary and innovative idea, regardless of the external environmental disturbances. Studying the growth and tuber yield of potatoes (Solanum tuberosum L.) in an LED-based plant factory system is a relatively [...] Read more.
Plant growing using light-emitting diodes (LEDs) in a controlled environment is a revolutionary and innovative idea, regardless of the external environmental disturbances. Studying the growth and tuber yield of potatoes (Solanum tuberosum L.) in an LED-based plant factory system is a relatively innovative concept. The current study was conducted in a plant factory to evaluate the effects of different LED spectral compositions on potato tuberization. Potato tuberization was analyzed under six different LED light spectral combinations with irradiances of 300 mol m−2 s−1, with natural light considered the control treatment. The findings stated that the L2 treatment (red70 + blue20 + white10) increased the plant height, branch number, and biomass accumulation, while photosynthetic pigments and photosynthetic activity increased significantly in L5 (red60 + blue20 + green10 + white10). Higher gibberellic acid (GA3) content was recorded in L1 (red70 + blue30), whereas the tuber number and tuber fresh weight were recorded in L3 (red70 + blue20 + green10) and L7 (natural light), respectively. On the other hand, a higher number of smaller-sized tubers were observed in L5, while L2 and L4 (red70 + blue20 + far-red10) resulted in a higher number of medium-sized tubers. In conclusion, a high proportion of red and blue light, along with white and far-red light, increased the plant height, branch number, plant biomass, and production of small- and medium-sized tubers. On the other hand, the inclusion of green light with red and blue enhanced the chlorophyll content, photosynthesis, and leaf expansion, and promoted the production of smaller-sized tubers. Finally, with regard to tuberization, the treatment using L4 followed by L2 outperformed the other treatments. Full article
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15 pages, 628 KiB  
Article
Can LED Lighting Be a Sustainable Solution for Producing Nutritionally Valuable Microgreens?
by Roberta Vrkić, Jana Šic Žlabur, Mia Dujmović and Božidar Benko
Horticulturae 2024, 10(3), 249; https://doi.org/10.3390/horticulturae10030249 - 5 Mar 2024
Viewed by 881
Abstract
With its quality, intensity, and photoperiod, light is a decisive abiotic factor that directly influences plant biomass and the accumulation of specialized metabolites (SMs). Photosynthetically active radiation (PAR) has significant effects on primary and secondary plant metabolism and thus influences the morphological characteristics [...] Read more.
With its quality, intensity, and photoperiod, light is a decisive abiotic factor that directly influences plant biomass and the accumulation of specialized metabolites (SMs). Photosynthetically active radiation (PAR) has significant effects on primary and secondary plant metabolism and thus influences the morphological characteristics of plants and their antioxidant systems. The aim of this study was to investigate the effects of blue, red, and a 50:50 combination of blue and red LED lighting on the SM content in broccoli, mustard, and garden cress microgreens grown in an indoor farm using the zero-acreage farming technique (ZFarming). This research aims to provide valuable insights into the optimization of light spectra to improve the nutritional quality of microgreens, with a focus on sustainable and space-saving cultivation methods. After eight days, the samples were cut in the cotyledon phenophase and analyzed in a fresh state. The microgreens grown under the blue spectrum LED lighting had the highest content of ascorbic acid (112.70 mg·100 g fw−1), total phenolics (412.39 mg GAE·100 g fw−1), and the highest antioxidant capacity (2443.62 µmol TE·L−1). The results show that the highest content of SMs in all the studied microgreens species was accumulated under the blue spectrum LED lighting. This study underlines the favorable influence of the blue spectrum (400–500 nm) on the nutrient content, especially the enhancement of SMs, in the microgreens investigated. Furthermore, the use of supplemental LED lighting proves to be a sustainable and effective means of producing microgreens with superior nutritional properties through the innovative practice of the zero-acreage farming technique. Full article
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17 pages, 2350 KiB  
Article
Comparison of Methods to Determine Nutrient Uptake of Tomato Grown in Free-Draining Perlite Substrate—Key Information for Optimal Fertigation Management
by Juan M. Cedeño, Juan-José Magán, Rodney Bruce Thompson, María-Dolores Fernández and Marisa Gallardo
Horticulturae 2024, 10(3), 232; https://doi.org/10.3390/horticulturae10030232 - 28 Feb 2024
Viewed by 1472
Abstract
Two methods were compared to determine crop nutrient uptake by tomato crops in free-draining perlite substrate. They were the nutrient balance method (applied minus drained) and the dry matter method (DM) (nutrients in plant material). Uptake of N, P, K, Ca, Mg, and [...] Read more.
Two methods were compared to determine crop nutrient uptake by tomato crops in free-draining perlite substrate. They were the nutrient balance method (applied minus drained) and the dry matter method (DM) (nutrients in plant material). Uptake of N, P, K, Ca, Mg, and S was determined using both methods, in three consecutive tomato crops planted in the same perlite. Nutrient uptake determined using the balance method was consistently higher than with the DM method. Relative differences (balance minus dry matter, with respect to the DM method) were N: −1 to 16%, P: 27–45%, K: 14–46%, Ca: 17–87%, Mg: 28–111%, and S: 15–65%. There was a clear tendency for the difference between the methods to reduce with successive crops. The differences between the methods were reduced when the measured retention of nutrients in the perlite substrate and estimated nutrient retention in roots (using a model) were included. However, these data did not explain all of the observed differences between the two methods. Various retention and loss processes may explain the differences. The results suggest that the DM matter method estimates nutrient uptake by the crop, and the balance method estimates nutrient consumption by the cropping system. Full article
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19 pages, 4545 KiB  
Article
Combining Recurrent Neural Network and Sigmoid Growth Models for Short-Term Temperature Forecasting and Tomato Growth Prediction in a Plastic Greenhouse
by Yi-Shan Lin, Shih-Lun Fang, Le Kang, Chu-Chung Chen, Min-Hwi Yao and Bo-Jein Kuo
Horticulturae 2024, 10(3), 230; https://doi.org/10.3390/horticulturae10030230 - 27 Feb 2024
Cited by 1 | Viewed by 930
Abstract
Compared with open-field cultivation, greenhouses can provide favorable conditions for crops to grow through environmental control. The prediction of greenhouse microclimates is a way to reduce environmental monitoring costs. This study used several recurrent neural network models, including long short-term memory (LSTM), gated [...] Read more.
Compared with open-field cultivation, greenhouses can provide favorable conditions for crops to grow through environmental control. The prediction of greenhouse microclimates is a way to reduce environmental monitoring costs. This study used several recurrent neural network models, including long short-term memory (LSTM), gated recurrent unit, and bi-directional LSTM, with varying numbers of hidden layers and units, to establish a temperature forecasting model for a plastic greenhouse. To assess the generalizability of the proposed model, the most accurate forecasting model was used to predict the temperature in a greenhouse with different specifications. During a test period of four months, the best proposed model’s R2, MAPE, and RMSE values were 0.962, 3.216%, and 1.196 °C, respectively. Subsequently, the outputs of the temperature forecasting model were used to calculate growing degree days (GDDs), and the predicted GDDs were used as an input variable for the sigmoid growth models to simulate the leaf area index, fresh fruit weight, and aboveground dry matter of tomatoes. The R2 values of the growth model for the three growth traits were all higher than 0.80. Moreover, the fitted values and the parameter estimates of the growth models were similar, irrespective of whether the observed GDD (calculated using the actual observed data) or the predicted GDD (calculated using the temperature forecasting model output) was used. These results indicated that the proposed temperature forecasting model could accurately predict the temperature changes inside a greenhouse and could subsequently be used for the growth prediction of greenhouse tomatoes. Full article
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32 pages, 19325 KiB  
Article
Seedling Growth Stress Quantification Based on Environmental Factors Using Sensor Fusion and Image Processing
by Sumaiya Islam, Md Nasim Reza, Shahriar Ahmed, Samsuzzaman, Yeon Jin Cho, Dong Hee Noh and Sun-Ok Chung
Horticulturae 2024, 10(2), 186; https://doi.org/10.3390/horticulturae10020186 - 18 Feb 2024
Viewed by 972
Abstract
Understanding the diverse environmental influences on seedling growth is critical for maximizing yields. The need for a more comprehensive understanding of how various environmental factors affect seedling growth is required. Integrating sensor data and image processing techniques offers a promising approach to accurately [...] Read more.
Understanding the diverse environmental influences on seedling growth is critical for maximizing yields. The need for a more comprehensive understanding of how various environmental factors affect seedling growth is required. Integrating sensor data and image processing techniques offers a promising approach to accurately detect stress symptoms and uncover hidden patterns, enhancing the comprehension of seedling responses to environmental factors. The objective of this study was to quantify environmental stress symptoms for six seedling varieties using image-extracted feature characteristics. Three sensors were used: an RGB camera for color, shape, and size information; a thermal camera for measuring canopy temperature; and a depth camera for providing seedling height from the image-extracted features. Six seedling varieties were grown under controlled conditions, with variations in temperature, light intensity, nutrients, and water supply, while daily automated imaging was conducted for two weeks. Key seedling features, including leaf area, leaf color, seedling height, and canopy temperature, were derived through image processing techniques. These features were then employed to quantify stress symptoms for each seedling type. The analysis of stress effects on the six seedling varieties revealed distinct responses to environmental stressors. Integration of color, size, and shape parameters established a visual hierarchy: pepper and pak choi seedlings showed a good response, cucumber seedlings showed a milder response, and lettuce and tomato seedlings displayed an intermediate response. Pepper and tomato seedlings exhibited a wide range of growth stress symptoms, at 13.00% to 83.33% and 2.96% to 70.01%, respectively, indicating considerable variability in their reactions to environmental stressors. The suggested classification approach provides valuable groundwork for advancing stress monitoring and enabling growers to optimize environmental conditions. Full article
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22 pages, 7159 KiB  
Article
Layout of Suspension-Type Small-Sized Dehumidifiers Affects Humidity Variability and Energy Consumption in Greenhouses
by Md Ashrafuzzaman Gulandaz, Md Sazzadul Kabir, Md Shaha Nur Kabir, Mohammod Ali, Md Nasim Reza, Md Asrakul Haque, Geun-Hyeok Jang and Sun-Ok Chung
Horticulturae 2024, 10(1), 63; https://doi.org/10.3390/horticulturae10010063 - 8 Jan 2024
Viewed by 1220
Abstract
In greenhouse management, maintaining optimal humidity is essential for promoting plant growth, including photosynthesis, and preventing diseases and pests. Addressing spatial variability requires sensor-based monitoring for informed decisions on humidification systems, particularly for small, and suspension-type dehumidifiers. This study aims to assess the [...] Read more.
In greenhouse management, maintaining optimal humidity is essential for promoting plant growth, including photosynthesis, and preventing diseases and pests. Addressing spatial variability requires sensor-based monitoring for informed decisions on humidification systems, particularly for small, and suspension-type dehumidifiers. This study aims to assess the impact of various layouts of small-sized suspension-type dehumidifiers on vertical, spatial, and temporal humidity variability, along with energy consumption in a greenhouse. During experiments in a 648 m³ (18 m × 6 m × 6 m) plastic greenhouse, dehumidifiers were placed at four different layouts: one at the center (Layout 1), one on each side (Layout 2), two units at the center facing opposite directions (Layout 3), and two units on one side facing the center (Layout 4). Temperature and humidity (TH) sensors were connected to a microcontroller, facilitating wireless data acquisition, storage, and remote monitoring. The actuator was controlled through a relay module, and current sensors monitored power consumption. Spatial interpolation and mapping were employed using mapping software. These layouts reduced humidity from 89.30% to 51.10%, with Layout 2 displaying the most consistent humidity distribution. Water removal efficiency varied among layouts, with Layout 2 exhibiting the highest (61.15 L) and overall performance of 50%, while Layouts 1, 3, and 4 exhibited lower efficiencies of 40%, 44%, and 49%, respectively. Power consumption ranged from 0.506 to 0.528 kW for the dehumidifier and 0.242 to 0.264 kW for the fan. The findings highlighted that positioning the dehumidifier on both sides, facing towards the center (Layout 2), resulted in the most uniform humidity control within the greenhouse. The optimal layout of small suspension-type dehumidifiers in greenhouses would significantly improve humidity control, promoting plant growth. Full article
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17 pages, 6253 KiB  
Article
Leaf Area Prediction of Pennywort Plants Grown in a Plant Factory Using Image Processing and an Artificial Neural Network
by Md Nasim Reza, Milon Chowdhury, Sumaiya Islam, Md Shaha Nur Kabir, Sang Un Park, Geung-Joo Lee, Jongki Cho and Sun-Ok Chung
Horticulturae 2023, 9(12), 1346; https://doi.org/10.3390/horticulturae9121346 - 17 Dec 2023
Viewed by 1095
Abstract
The leaf is a primary part of a plant, and examining the leaf area is crucial in understanding growth and plant physiology. Accurately estimating leaf area is key to this understanding. This study proposed a methodology for the non-destructive estimation of leaf area [...] Read more.
The leaf is a primary part of a plant, and examining the leaf area is crucial in understanding growth and plant physiology. Accurately estimating leaf area is key to this understanding. This study proposed a methodology for the non-destructive estimation of leaf area in pennywort plants using image processing and an artificial neural network (ANN) model. The image processing method involved a series of steps, including grayscale conversion, histogram equalization, binary masking, and region filling, achieving an accuracy of around 96.6%. The ANN model, trained with 70% of a dataset, exhibited high correlations of 97.1% in training and 96.6% in testing phases, with leaf length and width significantly impacting the model output. A comparative analysis revealed the superior performance of the ANN model over the image processing method, demonstrating higher R2 values (>0.99) and lower errors. Furthermore, it showed the impact of diverse LED light combinations and nutrient levels (electrical conductivity, EC) on pennywort plant growth, indicating that the R70:B30 LED light ratio with nutrient level 2 (2.0 dS·m−1) fostered the most favorable growth for pennywort plants. The non-destructive nature, simplicity, and speed of the ANN model in estimating leaf area based on easily obtainable measurements of length and width render it an accessible and accurate tool for plant growth assessment in controlled environments. This approach offers opportunities for future studies, tracking changes in leaf areas under varied growth conditions without harming the plant, thus enhancing precision in research. Full article
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13 pages, 3712 KiB  
Article
Prediction of Growth and Quality of Chinese Cabbage Seedlings Cultivated in Different Plug Cell Sizes via Analysis of Image Data Using Multispectral Camera
by Sehui Ban, Inseo Hong and Yurina Kwack
Horticulturae 2023, 9(12), 1288; https://doi.org/10.3390/horticulturae9121288 - 30 Nov 2023
Viewed by 1238
Abstract
In recent times, there has been an increasing demand for the development of rapid and non-destructive assessment of the growth and quality of seedlings before transplanting. This study was conducted to examine the growth and quality of Chinese cabbage seedlings that can be [...] Read more.
In recent times, there has been an increasing demand for the development of rapid and non-destructive assessment of the growth and quality of seedlings before transplanting. This study was conducted to examine the growth and quality of Chinese cabbage seedlings that can be determined via the image data acquired using a multispectral camera. Chinese cabbage seedlings were cultivated in five different plug trays (72, 105, 128, 162, and 200 cells/tray) for 30 days after sowing (DAS). The growth of seedlings had no significant difference in the early stage of cultivation; however, it decreased with increasing the number of cells in the plug tray due to the restricted root zone volume in the mid to late stages. Individual leaf area was predicted by analyzing of image data with high accuracy (R2 > 0.8) after 15 DAS; however, the accuracy of leaf area prediction per tray decreased due to overlapping and twisting leaves. Among six different vegetation indices, mrNDVI showed a high correlation (R2 > 0.6) with the dry weight of seedlings at 25 and 30 DAS. We confirmed that the leaf area of seedlings can be predicted non-destructively by analyzing the acquired image data per seedling and tray and suggested the applicability of vegetation indices for predicting the growth and quality of vegetable seedlings. Full article
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16 pages, 8637 KiB  
Article
Influence of Far-Red Intensity during the Seedling Stage on Biomass Production and Photomorphogenic Characteristics in Leafy Greens under Sole-Source Lighting
by Nathan J. Eylands and Neil S. Mattson
Horticulturae 2023, 9(10), 1100; https://doi.org/10.3390/horticulturae9101100 - 4 Oct 2023
Cited by 1 | Viewed by 1254
Abstract
It has been well documented that far-red radiation (FR; 700–799 nm) elicits a shade-avoidance/shade-tolerance response across a wide range of plant species. Most sole-source lighting is relatively low in FR compared to sunlight (i.e., 2% vs. 20% of photons, respectively, integrated between 400 [...] Read more.
It has been well documented that far-red radiation (FR; 700–799 nm) elicits a shade-avoidance/shade-tolerance response across a wide range of plant species. Most sole-source lighting is relatively low in FR compared to sunlight (i.e., 2% vs. 20% of photons, respectively, integrated between 400 and 799 nm). The objective of this experiment was to determine if the photomorphogenic response to FR is a useful strategy during the seedling stage to promote leaf expansion in the hopes that subsequently transplanted seedlings would increase radiation capture resulting in higher harvestable biomass. Lettuce (cv. ‘Rex’, ‘Red Oak’, and ‘Green Grand Rapids’) seedlings were exposed to 5, 10, 20, or 30 µmol·m−2·s−1 of supplemental FR for a duration of 10 d in a growth chamber for 20 h daily. During this stage, all seedlings received background light levels of 195 µmol·m−2·s−1 PAR light from white LEDs for 20 h daily. Seedlings were transplanted into a nutrient film technique (NFT) hydroponic system in a separate growth chamber with LED fixtures that supplied white light at 295 µmol·m−2·s−1 for 16 h daily (DLI = 17 mol·m−2·d−1) until they were harvested at 35 d from seeding. At transplant, fresh weight, leaf area, and plant height were significantly greater for all cultivars exposed to 30 µmol·m−2·s−1 of supplemental FR radiation compared to the 5 µmol·m−2·s−1 control. Fresh weight increased by an average of 35% under 30 µmol·m−2·s−1 FR. Mature plant dry biomass increased by 14% when seedlings were exposed to 30 µmol·m−2·s−1 of supplemental FR radiation. Increasing far-red radiation consistently increased plant growth at the seedling stage, but these increases were generally overcome by maturation. Full article
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11 pages, 1810 KiB  
Article
Forcing Temperature Effects on Plant Development for Containerized Blackberry Grown Using Long-Cane Techniques
by Ryan W. Dickson, Leala M. Machesney and Erika O. Henderson
Horticulturae 2023, 9(10), 1090; https://doi.org/10.3390/horticulturae9101090 - 30 Sep 2023
Viewed by 879
Abstract
Dormant containerized blackberry plants grown as long canes are forced into protected environments, such as plastic tunnels or greenhouses, to schedule harvesting for important market weeks. The time needed to produce a crop is mainly a function of temperature. In this study, the [...] Read more.
Dormant containerized blackberry plants grown as long canes are forced into protected environments, such as plastic tunnels or greenhouses, to schedule harvesting for important market weeks. The time needed to produce a crop is mainly a function of temperature. In this study, the objectives were to quantify the effects of temperature on plant development rates for long-cane blackberry and develop simple models predicting the time from forcing dormant plants to first open flowers and ripe fruit as a function of average daily temperature (ADT). The crop time and ADT at the first-flower and -fruit stages were measured for the cultivars ‘Loch Ness’, ‘Osage’, ‘Ponca’, and ‘Prime-Ark® 45′ grown as long canes during a greenhouse and high-tunnel experiment, and the days to flowering and fruiting were converted to rates by calculating the reciprocal. Nonlinear models relating flowering and fruiting rates to ADT were developed for each cultivar using a combination of the experimental data and base (6 °C), optimum (25 °C), and maximum (35 °C) temperature parameters derived from a previous blackberry heat unit study. Model accuracy was evaluated by comparing the predicted to observed times to first flower and fruit per cultivar. Average daily temperature was shown to have a main influence on crop timing, as shown by a strongly positive and near 1:1 relationship between predicted and observed days to flowering/fruiting. However, there was significant variability depending on the cultivar and model accuracy within ±7 days, ranging from 50% (‘Prime-Ark® 45) to 90% (‘Loch Ness’) for the flower models and from 60% (‘Prime-Ark® 45) to 100% (‘Loch Ness’) for the fruit models. To the best of our knowledge, this study is the first to characterize the relationship between temperature and crop timing for soilless long-cane blackberry, and it provides a framework for modeling temperature effects on crop timing for these systems. The authors discuss further methods to improve model accuracy and precision for commercial use. These models can also be used for general training purposes to help educate growers on how temperature influences crop scheduling during long-cane blackberry production. Full article
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18 pages, 3055 KiB  
Article
Prediction of Greenhouse Indoor Air Temperature Using Artificial Intelligence (AI) Combined with Sensitivity Analysis
by Pejman Hosseini Monjezi, Morteza Taki, Saman Abdanan Mehdizadeh, Abbas Rohani and Md Shamim Ahamed
Horticulturae 2023, 9(8), 853; https://doi.org/10.3390/horticulturae9080853 - 26 Jul 2023
Cited by 2 | Viewed by 2334
Abstract
Greenhouses are essential for agricultural production in unfavorable climates. Accurate temperature predictions are critical for controlling Heating, Ventilation, Air-Conditioning, and Dehumidification (HVACD) and lighting systems to optimize plant growth and reduce financial losses. In this study, several machine models were employed to predict [...] Read more.
Greenhouses are essential for agricultural production in unfavorable climates. Accurate temperature predictions are critical for controlling Heating, Ventilation, Air-Conditioning, and Dehumidification (HVACD) and lighting systems to optimize plant growth and reduce financial losses. In this study, several machine models were employed to predict indoor air temperature in an even-span Mediterranean greenhouse. Radial Basis Function (RBF), Support Vector Machine (SVM), and Gaussian Process Regression (GPR) were applied using external parameters such as outside air, relative humidity, wind speed, and solar radiation. The results showed that an RBF model with the LM learning algorithm outperformed the SVM and GPR models. The RBF model had high accuracy and reliability with an RMSE of 0.82 °C, MAPE of 1.21%, TSSE of 474.07 °C, and EF of 1.00. Accurate temperature prediction can help farmers manage their crops and resources efficiently and reduce energy inefficiencies and lower yields. The integration of the RBF model into greenhouse control systems can lead to significant energy savings and cost reductions. Full article
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17 pages, 3624 KiB  
Article
Effects of CO2 Enrichment on Carbon Assimilation, Yield and Quality of Oriental Melon Cultivated in a Solar Greenhouse
by Xintong Han, Yue Sun, Junqin Chen, Zicong Wang, Hongyan Qi, Yufeng Liu and Yiling Liu
Horticulturae 2023, 9(5), 561; https://doi.org/10.3390/horticulturae9050561 - 9 May 2023
Viewed by 1552
Abstract
Since CO2 is the fundamental substrate for photosynthesis, fluctuating concentrations have a direct effect on plant growth and metabolism. Accordingly, CO2 enrichment within a certain range was found to improve photosynthesis, yields and the quality of plants. In order to further [...] Read more.
Since CO2 is the fundamental substrate for photosynthesis, fluctuating concentrations have a direct effect on plant growth and metabolism. Accordingly, CO2 enrichment within a certain range was found to improve photosynthesis, yields and the quality of plants. In order to further understand the underlying impact of CO2 enrichment, this study employed an open-top chamber growth box model with the following two treatments: control treatment (CO2 concentration: 380 ± 30 μL/L) and CO2 enrichment (1200 ± 50 μL/L). The effects on leaf carbon assimilation, fruit yield and quality were subsequently determined. The net photosynthetic rate, intercellular CO2 concentration, dry matter accumulation and soluble sugar content in the oriental melon leaves increased significantly on day 5 of CO2 enrichment. Moreover, a significant increase in the activity of carbon assimilation-related enzymes Rubisco, RCA, FBPase and CA was also observed, with the upregulation of CmRubisco, CmRCA, CmFBPase and CmCA gene expression from day 15 of CO2 enrichment. Thus, the yield per plant and content of soluble sugars and soluble solids in the fruit also increased significantly. These findings suggest that CO2 enrichment has positive effects on oriental melon growth, increasing photosynthesis and the activity of photosynthetic carbon-assimilation-related enzymes and associated gene expression, thereby improving fruit yields and quality. These results provide a foundation for the CO2 enrichment of oriental melon cultivated in solar greenhouses in autumn/winter and winter/spring. Full article
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17 pages, 2495 KiB  
Article
Light Intensity during Green-Leaf Butterhead Lettuce Propagation Influences Yield and Carotenoids at Harvest
by Spencer R. Givens, Dustin S. Del Moro, Sarah E. Parker, Alexander G. Renny, Carl E. Sams and Kellie J. Walters
Horticulturae 2023, 9(2), 223; https://doi.org/10.3390/horticulturae9020223 - 7 Feb 2023
Cited by 1 | Viewed by 1690
Abstract
Controlled environment agriculture (CEA) operations must increase resource-use efficiency, yield, and phytonutrient concentrations to remain competitive. Carotenoids are phytonutrients of interest due to their purported health promoting effects. Their content is impacted by environmental controls, including lighting. Light-use efficiency increases with greater planting [...] Read more.
Controlled environment agriculture (CEA) operations must increase resource-use efficiency, yield, and phytonutrient concentrations to remain competitive. Carotenoids are phytonutrients of interest due to their purported health promoting effects. Their content is impacted by environmental controls, including lighting. Light-use efficiency increases with greater planting density, which is highest during seedling production. This creates the opportunity to raise light intensity during seedling production to improve growth characteristics and phytonutrient concentrations at harvest. Therefore, the objective of this research was to quantify the extent to which light intensity influences carotenoid accumulation in green butterhead lettuce seedlings, and if differences remain at harvest. Lettuce ‘Rex’ (Lactuca sativa L.) seedlings were grown under fluorescent lighting with intensities of 60, 100, 200, 400, or 600 µmol·m−2·s−1 with a 24-h photoperiod. After 14 days, seedlings were transplanted into raft hydroponic systems in a common greenhouse environment and grown for 21 days. At transplant and final harvest, tissue samples were collected and stored at −80 °C for phytonutrient analysis. Carotenoids, β-carotene, lutein, neoxanthin, zeaxanthin, and violaxanthin, and chlorophylls a and b were quantified using high-performance liquid chromatography (HPLC). We observed a 475% fresh mass enhancement in seedlings grown under 400 versus 60 µmol·m−2·s−1, with a 174% improvement persisting to final harvest. Higher seedling light intensities also generally increased leaf numbers in seedlings and at final harvest, as well as seedling carotenoid concentrations. Final harvest carotenoid concentrations generally decreased with increasing light intensity. Thus, producers should be cognizant that seedling light intensity strongly influences seedling and finished production yield, morphology, and carotenoid content. Full article
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16 pages, 2866 KiB  
Article
Photosynthesis Characteristics of Tomato Plants and Its’ Responses to Microclimate in New Solar Greenhouse in North China
by Haijun Liu, Mengxuan Shao and Li Yang
Horticulturae 2023, 9(2), 197; https://doi.org/10.3390/horticulturae9020197 - 3 Feb 2023
Cited by 2 | Viewed by 2152
Abstract
With the increasing demand for vegetable fruits, vegetable plants are moved to protected structures for achieving high production and economic revenue, especially in undesirable seasons. In North China, tomato crops, as widely consumed vegetables, are now increasingly planted in solar greenhouses (GH), especially [...] Read more.
With the increasing demand for vegetable fruits, vegetable plants are moved to protected structures for achieving high production and economic revenue, especially in undesirable seasons. In North China, tomato crops, as widely consumed vegetables, are now increasingly planted in solar greenhouses (GH), especially in the winter period. To improve the microclimate inside GH in winter, a sunken solar greenhouse was used recently. This study was to evaluate the photosynthetic characteristics of tomato plants and its responses to the inside microclimate in this new GH. In this experiment, the plant transpiration (E) and photosynthesis (Pn) rates of healthy and diseased plants were measured from July to December for three growth seasons in a commercial GH in North China. Results show both E and Pn were positively related to inside radiation and vapor pressure deficit. The stomata conductance to E (gsw) and Pn (gtc) performed relatively constant during daytime, and weakly related to inside microclimate. The parameters of E, Pn, gsw and gtc were greatly reduced for diseased plants in summer because of the heat shock. The water use efficiency at the leaf level, the ratio of Pn to E, was higher for solar radiation of 400–500 W m−2, temperature of 20–30 °C, relative humidity of higher than 80%, and vapor pressure deficit of less than 2.0 kPa. The results of this study could help farmers in the region of 30 to 40 degrees north latitude to enhance the growth of tomato crops in winter by using this sunken solar greenhouse. Full article
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12 pages, 2098 KiB  
Article
The Impact of CO2 Enrichment on Biomass, Carotenoids, Xanthophyll, and Mineral Content of Lettuce (Lactuca sativa L.)
by Jake Holley, Neil Mattson, Eyosias Ashenafi and Marianne Nyman
Horticulturae 2022, 8(9), 820; https://doi.org/10.3390/horticulturae8090820 - 7 Sep 2022
Cited by 1 | Viewed by 1942
Abstract
Carbon dioxide (CO2) concentrations affect the growth rate of plants by increasing photosynthesis. Increasing CO2 in controlled environment agriculture (CEA) provides a means to boost yield or decrease daily light integral (DLI) requirements, potentially increasing profitability of growing operations. However, [...] Read more.
Carbon dioxide (CO2) concentrations affect the growth rate of plants by increasing photosynthesis. Increasing CO2 in controlled environment agriculture (CEA) provides a means to boost yield or decrease daily light integral (DLI) requirements, potentially increasing profitability of growing operations. However, increases in carbon dioxide concentrations are often correlated with decreased nutritional content of crops. The objectives of this experiment were to quantify the effects of carbon dioxide on the growth, morphology, and nutritional content of two lettuce varieties, ‘Rex’ and ‘Rouxai’ under four CO2 concentrations. Applied CO2 treatments were 400, 800, 1200, and 1600 ppm in controlled environment chambers with identical DLI. Lettuce was germinated for eight days in a greenhouse, then transplanted into potting mix and placed in a growth chamber illuminated by fluorescent lights. After 21 days, lettuce was destructively harvested, and fresh weight and plant volume were measured. Anthocyanins, xanthophylls, chlorophyll, and mineral concentration were measured. The lettuce fresh and dry weight increased with increasing CO2 concentrations, with the greatest increases observed between 400 and 800 ppm, and diminishing increases as CO2 concentration further increased to 1200 and 1600 ppm. Violaxanthin was observed to decrease in ‘Rouxai’ with increasing CO2 concentration. Largely, no significant differences were observed in lutein, anthocyanins, and mineral content. Overall, increasing concentrations of carbon dioxide can significantly increase the yield for lettuce in controlled environments, while not significantly reducing many of the nutritional components. Full article
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12 pages, 1551 KiB  
Article
Response of Common Ice Plant (Mesembryanthemum crystallinum L.) to Photoperiod/Daily Light Integral in Vertical Hydroponic Production
by Jiaqi Xia and Neil Mattson
Horticulturae 2022, 8(7), 653; https://doi.org/10.3390/horticulturae8070653 - 19 Jul 2022
Cited by 4 | Viewed by 2774
Abstract
Common ice plant (Mesembryanthemum crystallinum L.) is a novel edible plant with a succulent and savory flavor emerging as new crop for greenhouse and plant factory growers. Currently very limited information is available on the response of ice plant to photoperiod and [...] Read more.
Common ice plant (Mesembryanthemum crystallinum L.) is a novel edible plant with a succulent and savory flavor emerging as new crop for greenhouse and plant factory growers. Currently very limited information is available on the response of ice plant to photoperiod and to daily light integral (DLI). The objective of this study was to determine the impact of photoperiod/DLI on the growth of ice plant for indoor vertical production. Four-week old seedlings of ice plant were transplanted into vertical hydroponic systems and given five photoperiod/DLI treatments: 8/6.3, 12/9.5, 16/12.7, 20/15.8, and 24/19.0 h/mol·m−2·d−1. Sequential destructive harvests to determine plant growth occurred 14, 21, and 28 days after lighting treatments began. Plants performed better with increasing photoperiod/DLI from 8 h/6.3 mol·m−2·d−1 to 20 h/15.8 mol·m−2·d−1. By day 28, shoot fresh weight increased from 160 g to 639 g as the photoperiod/DLI increased from 8 h/6.3 mol·m−2·d−1 to 20 h/15.8 mol·m−2·d−1. The continuous lighting treatment, 24 h/19 mol·m−2·d−1, showed a negative effect on the plant fresh weight (FW) and dry weight (DW). Light treatment did not have obvious effects on shoot:root ratio and macronutrient uptake except that potassium (K) uptake decreased slightly with increased photoperiod/DLI. Plants receiving higher photoperiod/DLI showed the same number of leaves (indicating the same development stage) but had smaller, thicker, and darker green leaves compared to lower photoperiod/DLI treatments. Leaf water content was not affected by light treatment up to 20 h/15.8 mol·m−2·d−1 but decreased at 24 h/19 mol·m−2·d−1. Further research is needed to separate the physiological response of increasing/continuous photoperiod from the response of increasing DLI. Full article
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Review

Jump to: Research

47 pages, 10775 KiB  
Review
Technological Trends and Engineering Issues on Vertical Farms: A Review
by Md Shaha Nur Kabir, Md Nasim Reza, Milon Chowdhury, Mohammod Ali, Samsuzzaman, Md Razob Ali, Ka Young Lee and Sun-Ok Chung
Horticulturae 2023, 9(11), 1229; https://doi.org/10.3390/horticulturae9111229 - 15 Nov 2023
Cited by 3 | Viewed by 5854
Abstract
Vertical farming has emerged as a promising solution to cope with increasing food demand, urbanization pressure, and limited resources and to ensure sustainable year-round urban agriculture. The aim of this review was to investigate the evolving technological landscape and engineering considerations, with a [...] Read more.
Vertical farming has emerged as a promising solution to cope with increasing food demand, urbanization pressure, and limited resources and to ensure sustainable year-round urban agriculture. The aim of this review was to investigate the evolving technological landscape and engineering considerations, with a focus on innovative developments and future prospects. This paper presents technological trends in vertical farming, covering advances in sensing technologies, monitoring and control systems, and unmanned systems. It also highlights the growing role of artificial intelligence (AI) in contributing to data-driven decision-making and the optimization of vertical farms. A global perspective on vertical farming is presented, including the current status and advanced technological trends across regions like Asia, the USA, and Europe. Innovative concepts and upcoming enterprises that could shape the future of vertical agriculture are explored. Additionally, the challenges and future prospects of vertical farming are also addressed, focusing on crop production limitations, environmental sustainability, economic feasibility, and contributions to global food security. This review provides guidance on the state of vertical farming, technological advancements, global trends, challenges, and prospects, offering insights into the roles of researchers, practitioners, and policymakers in advancing sustainable vertical agriculture and food security. Full article
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