Modeling the Effect of Temperature on the Flower Development Rate of Hybrid Impatiens

The effect of average daily temperature (ADT) on flower bud development and subsequent time to flower was investigated on hybrid impatiens (Impatiens ×hybrida) cultivars Compact Electric Orange, Compact Hot Coral, and Compact Orchid Blush. Plants with a visible flower bud measuring 2 mm in width were placed in one of the four greenhouses with temperature setpoints ranging from 16 to 28 °C. Flower bud width was measured every 3 days in each ADT treatment until flowering. The subsequent days to flower (DTF) from the onset of a visible bud decreased from 36 to 27 days as the ADT increased from 17 to 28 °C. The DTF from visible bud varied by <3 days among the three cultivars across all temperatures; therefore, cultivar data were pooled to create a stronger prediction model. A logistic formula was used to predict the remaining DTF as a function of flower bud width and ADT. The model accurately described the effect of bud width and ADT on flowering time within ±3 days for 87% of the actual DTF across all three cultivars. The resulting flower development model provides greenhouse growers with a guide for manipulating temperature to produce flowering plants for specific market dates based on flower bud width measurements.

Evaluating the Fertilising Potential of Blended Recovered Nutrients in Horticultural Growing Medium on Viola x wittrockiana L.

Viola x wittrockiana L. is an ornamental plant in high demand in horticulture. It is becoming more critical for greenhouse growers to focus on sustainable production to enhance plant quality while reducing negative environmental impacts. Therefore, assessing the effect of recycled phosphorous (P) and nitrogen (N) sources on the growth of viola could become very useful for producers in terms of sustainability. This experiment analysed the optimal fertiliser composition to grow viola using recovered fertilisers in a greenhouse trial under controlled conditions. Well-rooted viola plugs were grown in a standard peat-based growing medium. Using recycled sources of P and N as struvite and potassium struvite, ammonium sulphate, and ammonium nitrate, 14 fertiliser blends were prepared, tested, and compared with the slow-release commercial fertiliser Osmocote. Plants treated with ammonium nitrate showed healthy growth and optimal plant N concentrations. In contrast, most blends using the recovered ammonium sulphate resulted in an unacceptable increase of ammonium concentrations in the growing medium. The combination of ammonium sulphate and potassium sulphate caused an increase in the electrical conductivity in the growing medium, negatively affecting plant growth. However, blend 13 containing struvite, ammonium sulphate and potassium struvite expressed the best chemical composition with non-significant differences in the biomass from the positive controls, as it reduced the amount of potassium sulphate needed. Our results indicate that fertiliser blends containing P as struvite, N as ammonium nitrate or reduced amount of ammonium sulphate, and K as potassium struvite can substitute the use of mineral fertiliser blends to grow ornamental plant species as viola.

On the Technical Performance Characteristics of Horticultural Lamps

Recent advances in light emitting diode (LED) technology have provided exciting opportunities for plant lighting applications, and it is expected that LED lighting will soon overtake the still common use of high-intensity discharge (HID) lighting technology. Because LED lighting offers novel capabilities, extensive research is needed to identify optimal lighting practices for the large number of crops grown by commercial greenhouse growers. Plant scientists and growers facing decisions about plant lighting systems do not always have sufficient information about lamp performance characteristics. In this paper, we reported on various technical performance characteristics for 18 lamp types commonly used for plant production, and compared these characteristics with the characteristics of sunlight. The results showed a substantial range of performance characteristics, highlighting the importance of a careful assessment before selecting a light source for horticultural applications. The data presented in this paper can be used to assess the suitability of a specific light source for a particular horticultural application.

Supraoptimal Root-zone Temperatures Affect Dahlia Growth and Development

Dahlia (Dahlia ×hybrida) is an important floriculture crop that has gained popularity in recent years. Greenhouse growers have recently reported a phenomenon known as “dahlia decline,” that can affect potted dahlias in greenhouse production. The crop exhibits graying foliage, root decline, and plant death, and the phenomenon has reportedly caused partial or total crop loss and has no known initiating factor. We hypothesized that plant exposure to supraoptimal root-zone temperatures (RZTs) during production may decrease dahlia root quality, especially above 40 °C and could initiate dahlia decline. Because there is a lack of understanding on how supraoptimal RZT may impact dahlia growth and development, experiments were conducted to evaluate the effects of supraoptimal RZTs on seven dahlia cultivars in Spring 2019 and 2020. Dahlias were grown for 4 to 5 weeks in the greenhouse and then root zones were exposed to ≈22 (control), 35, 40, 45, or 50 °C using a water bath. Root quality was rated before treatment and rated weekly after the hot water bath treatment, along with vegetative growth parameters for 4 weeks. In both years, significant decline in root ratings were observed. ‘XXL Veracruz’ and ‘XXL Sunset’ average root ratings decreased after a 45 and 50 °C treatments in year 2 and both cultivars demonstrated increased root rating averages by 3 weeks after treatment. Cultivars exhibited a significant increase in root rating in the final observations when compared with root ratings taken 1 week posttreatment even if the initial decline after treatment was not significant. Overall plant height was significantly impacted, resulting in shorter heights in both years for all cultivars as treatment temperatures increased to 50 °C in comparison with the control and 35 °C, and a few cultivars exhibited significantly shorter height at 40 and 45 °C. Ultimately, our research did not show typical plant responses that were consistent with reported dahlia decline, but we were better able to characterize dahlia response to supraoptimal RZT.

Agent based coordination protocol for system of cyber-physical systems

Nowadays, society and business rely heavily on Information and Communication Technology (ICT) systems, which are progressing faster than ever. To stay on pace with them, focus is shifted towards integration of individual ICT systems into complex systems, which offers more functionality than simply the sum of individual systems. In this regard, Cyber-Physical Systems (CPSs) have gained significant importance and System-of-Systems (SoS) approach has been suggested for modeling complex CPSs to achieve a higher level goal, by dynamically building a large system with existing autonomous, and heterogeneous constituent systems (CSs). An important challenge in a system of Cyber-Physical Systems (SoCPSs) is to develop seamless collaboration between autonomous constituent-CPSs (CCPSs) to coordinate their operations. In this paper, we propose an agent based coordination mechanism to coordinate resource allocation and demand in SoCPSs. The approach models each CCPS as an agent and describes how multiple autonomous CCPSs, i.e., Virtual Power Plant (VPP), Commercial Greenhouse Growers (CGGs), communicate and collaborate with each other asynchronously through negotiation and how potential conflicts between CCPSs with conflicting goals are resolved. The efficacy of the proposed mechanism is validated through simulation of different real-world acyclic SoCPSs topologies. The results show that proposed approach is able to balance the individual requirements of multiple connected CPSs while achieving SoCPSs’ mission.

Occupational health risk management system for greenhouse vegetable growers

Introduction. Prevention of chronic general somatic diseases associated with exposure to harmful working conditions is one of the primary measures to preserve the health of the working population and labor resources of the Russian Federation. However, insufficient attention is paid to the management of occupational health risks of agricultural workers, including greenhouse vegetable growers. Materials and methods. Hygienic and epidemiological studies were carried out based on the methodology for assessing and managing occupational health risks. Results. A complex of harmful occupational factors, including high temperatures and humidity, harmful chemicals, including pesticides, plant dust, and the labor process’s severity simultaneously affect working greenhouse growers. Working conditions were assessed as harmful (classes 3.2-3.3) of occupational risk categories from medium to high. Direct statistically significant correlations were established between the length of occupational service and diseases of the respiratory system, circulatory system, musculoskeletal system, and connective tissue (respectively r = 0.58; r = 0.6; r = 0.35). A high degree of causal relationship with the work in harmful occupational conditions of arterial hypertension (RR = 2.805; EF = 64.35%; CI = 1.498-5.253), radiculopathy of the lumbosacral spine (RR = 2.290; EF = 56%; CI = 1.140- 4.599), an average degree of uterine fibroids (RR = 1.969; EF = 49%; CI = 0.988-3.926) and chronic bronchitis (RR = 1.532; EF = 34.7%; CI = 0.682-3.442), which allows classifying them as occupationally conditioned. The system of preventive measures to minimize occupational risks and prevent occupational diseases has been scientifically substantiated. Conclusion. Current working conditions of greenhouse vegetable growers are characterized by the impact of harmful occupational factors promoting occupationally caused diseases, which requires the implementation of a set of preventive measures based on a risk-oriented approach.

First report of Powdery Mildew Caused by Golovinomyces ambrosiae on Cannabis sativa in Oregon

Oregon is the second largest producer of hemp in the United States with 25,900 ha of hemp licensed to growers in 2019, a nearly six-fold increase over the previous year (Perkowski 2019, Capital Press). Industrial hemp has a wide range of uses including textiles to nutritional supplements; in Oregon, hemp has become one of the most economically promising crops and is mainly cultivated for cannabidiol (CBD) production. Between 2018 and 2019, multiple independent greenhouse growers in western Oregon reported powdery mildew-like signs and symptoms on leaves and buds of several Cannabis sativa cultivars, including ‘Cherry Wine’. Signs of the disease started as small, white, powdery patches, typically on the adaxial sides of leaves, and progressed to coalescent colonies on leaves, stems, and buds. Fungi present on diseased tissues had unbranched hyaline conidiophores that measured 140 to 250 µm and grew erect from caulicolous and amphigenous mycelium (n = 15). Foot cells were cylindrical, often tapered at one or both ends, and measured 80 to 117 × 9.5 to 11.9 µm (n = 15). Conidia were catenescent, hyaline, ellipsoidal to barrel-shaped, lacked fibrosin bodies, and measured 24 to 34 × 12 to 18 µm (n = 50). No chasmothecia were observed. Morphological observations overlapped with several Golovinomyces spp. Including G. ambrosiae, G. cichoracearum, and G. spadiceus (Braun and Cook 2012). Identification was confirmed by bidirectional sequencing and phylogenetic analysis of 1,457 nucleotides from the concatenated internal transcribed spacer (ITS), 28S large ribosomal subunit, and beta-tubulin (TUB2) regions of two isolates using primer pairs ITS1/ITS4 and NL1/LR5, and TubF1/TubR1 respectively (Mori et al. 2000, Qiu et al. 2020, Vilgalys and Hester 1990, White et al. 1990; GenBank Acc. No.: MW248121 to MW248124, MW265971 to MW265972). The Oregon hemp isolates grouped (bootstrap value = 100) in a monophyletic clade with G. ambrosiae accessions from Qiu et al. (2020). Pathogenicity was confirmed by transferring conidia by leaf rub inoculation onto 2-to 4-week-old ‘Cherry Wine’ potted plants and incubated outdoors at 12 to 22°C. Control plants were mock-inoculated using healthy leaves. Powdery mildew symptoms developed on inoculated plants approximately 14 to 21 days later; control plants were asymptomatic. Identification was confirmed by morphological characterization and sequencing using the aforementioned primers. The hemp isolates were also able to infect detached leaves of Humulus lupulus ‘Symphony’ via similar inoculations; however, colony development on ‘Symphony’ was slow and sporulation sparse as was reported by Weldon et al. (2020). Golovinomyces spp. have also been reported on hemp in Kentucky (Szarka et al. 2019), Ohio (Farinas and Peduto Hand 2020), and New York (Weldon et al. 2020). Although reported as G. spadiceus, these reports are also likely G. ambrosiae according to new taxonomic revision of the genus (Qiu et al. 2020). This is the first known report of Golovinomyces ambrosiae causing powdery mildew on hemp in Oregon (OSC 171893). While powdery mildew on hemp currently appears most severe in protected cultivation, rapid expansion of hemp cultivation and introduction of new CBD varieties throughout Oregon could lead to increased powdery mildew risk in outdoor cultivation.

Growing Medium Type Affects Organic Fertilizer Mineralization and CNPS Microbial Enzyme Activities

Managing plant fertilization is a major concern of greenhouse growers to achieve sustainable production with growing media (GM). Organic fertilization is popular but is more difficult to control, since organic compounds need first to be mineralized by microbes. After 7, 14, 28, and 56 days of incubation, we investigated the response of microbial activities and nutrient releases from three frequently used organic fertilizers (horn and two plant-based fertilizers) in three frequently employed GM types (peat, coir, and bark). We measured pH, electrical conductivity, nutrient contents (NH4+-N, NO3−-N, PO43−-P, SO42−-S), and enzyme activities (β-1.4-glucosidase, urease, acid phosphatase, arylsulfatase). After fertilization, microbes in coir expressed all the C, N, P, and S functions studied, making related nutrients available. In peat and bark, some C, N, P, and S-related pathways were locked. Peat presented high NH4+-N and PO43−-P releases linked to high acid phosphatase and β-glucosidase activities, while bark showed high nitrification rates but weak enzyme activities. Fertilizer types modulated these responses with lower activities and nutrient releases with horn. Our results contributed to better understanding mineralization processes in GM, showing different microbial responses to fertilization. This study pointed out the necessity to look deeper into microbial functions in GM optimizing biological and physicochemical properties.

Cherry Tomato Production in Intelligent Greenhouses—Sensors and AI for Control of Climate, Irrigation, Crop Yield, and Quality

Greenhouses and indoor farming systems play an important role in providing fresh and nutritious food for the growing global population. Farms are becoming larger and greenhouse growers need to make complex decisions to maximize production and minimize resource use while meeting market requirements. However, highly skilled labor is increasingly lacking in the greenhouse sector. Moreover, extreme events such as the COVID-19 pandemic, can make farms temporarily less accessible. This highlights the need for more autonomous and remote-control strategies for greenhouse production. This paper describes and analyzes the results of the second “Autonomous Greenhouse Challenge”. In this challenge, an experiment was conducted in six high-tech greenhouse compartments during a period of six months of cherry tomato growing. The primary goal of the greenhouse operation was to maximize net profit, by controlling the greenhouse climate and crop with AI techniques. Five international teams with backgrounds in AI and horticulture were challenged in a competition to operate their own compartment remotely. They developed intelligent algorithms and use sensor data to determine climate setpoints and crop management strategy. All AI supported teams outperformed a human-operated greenhouse that served as reference. From the results obtained by the teams and from the analysis of the different climate-crop strategies, it was possible to detect challenges and opportunities for the future implementation of remote-control systems in greenhouse production.