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Background The tea plant ( Camellia sinensis (L.) O. Kuntze) is one of the most economically important woody crops. Plastic greenhouse covering cultivation has been widely used in tea areas of northern China. Chlorophyll is not only the crucial pigment for green tea, but also plays an important role in the growth and development of tea plants. Currently, little is known about the effect of plastic greenhouse covering cultivation on chlorophyll in tea leaves. Results To investigate the effect of plastic greenhouse covering cultivation on chlorophyll in tea leaves, color difference values, chlorophyll contents, gene expression, enzyme activities and photosynthetic parameters were analyzed in our study. Sensory evaluation showed the color of appearance, liquor and infused leaves of greenhouse tea was greener than field tea. Color difference analysis for tea liquor revealed that the value of ∆L, ∆b and b/a of greenhouse tea was significantly higher than field tea. Significant increase in chlorophyll content, intracellular CO 2 , stomatal conductance, transpiration rate, and net photosynthetic rate was observed in greenhouse tea leaves. The gene expression and activities of chlorophyll-metabolism-related enzymes in tea leaves were also activated by greenhouse covering. Conclusion The higher contents of chlorophyll a, chlorophyll b and total chlorophyll in greenhouse tea samples were primarily due to higher gene expression and activities of chlorophyll-metabolism-related enzymes especially, chlorophyll a synthetase (chlG), pheophorbide a oxygenase (PAO) and chlorophyllide a oxygenase (CAO) in tea leaves covered by greenhouse. In general, our results revealed the molecular basis of chlorophyll metabolism in tea leaves caused by plastic greenhouse covering cultivation, which had great significance in production of greenhouse tea.

The natural ventilation model plays a crucial role in greenhouse environmental control. It has been extensively studied by previous researchers, but it is limited to low-altitude areas. This study established a numerical model of single-span plastic greenhouses in high-altitude areas. The model was validated using measured data, showing a good agreement between the measured and simulated values. By setting boundary conditions based on on-site monitoring data, ventilation rates were extracted under different conditions for numerical simulations. Through nonlinear fitting, an empirical formula for natural ventilation rates, with a determination coefficient (R2) of 0.9724, was derived. The formula was validated through an energy balance analysis of indoor air. Different ventilation opening sizes were simulated to derive an empirical formula for natural ventilation rates based on opening size. Building on this, the relationship between plant height and ventilation rate was analyzed. As the dominant factors of natural ventilation change with environmental fluctuations, this study also proposed the threshold wind speed for wind pressure ventilation, thermal pressure ventilation, and coupled ventilation, filling the knowledge gap in relevant ventilation rate calculations. This is the first time that a natural ventilation model of single-span plastic greenhouses in high-altitude areas has been proposed, providing the basis in terms of modeling for the further development of local facility agriculture.

The single-span plastic greenhouses are affected by strong winds which generate uplift resistance causing the bending of members, damage to protective films, and damage to crops. This study performed a field test using the static axial tensile load method to present basic data to prevent damage to a single-span plastic greenhouse. Three representative areas were selected, and the effects of pipe connectors, rafter spacing, and embedding depth were tested. In the field test results, it was found to be greatly affected by the pipe connector. The pull-out resistance at the site fixed by welding instead of the pipe connector was measured as 4.5 times the sliding resistance standard value of the Rural Development Administration. In other sites, the measurement was below the standard value of the sliding resistance of the pipe connector. It was confirmed that the uplift resistance is determined by the sliding resistance of the pipe connector, the rafters, and the crossbar pipe. Therefore, it seems possible to increase the uplift resistance of a single-span plastic greenhouses continuous foundation through the reinforcement of the pipe connector. The field test results can be utilized as basic data for the reinforcement of the commercialization of single-span plastic greenhouses and new standards.

The extent to how Escherichia coli O157:H7 can survive in soil and the predominant factors that determine its survival are crucial issues from a public health point of view. This study investigated the survival of E. coli O157:H7 in vegetable soils in plastic-greenhouse cultivation over 0, 1, 4, 8, and 12 years in southern China. Results showed that the survival times ( t ) calculated from the Weibull model for the five tested soils ranged from 9.00 to 21.11 days. In general, E. coli O157:H7 survived longer in open-field soils than in greenhouse soils under the same incubation conditions. The t values were greater in soils with a lower level of electrical conductivity, a higher level of total nitrogen, and a higher level of sand content. Compared to other factors, electrical conductivity was the most important factor affecting the survival of E. coli O157:H7 in the tested soils. Different survival times of E. coli O157:H7 in vegetable soils under diverse cultivation patterns highlight the importance of preventing pathogenic contamination for the purpose of food safety.

Aims Greenhouse tomatoes production with high productivity but also with high fertilizer inputs has rapidly developed in the Yangtze River Delta. It is a great significance to explore methods for reducing environmental cost for the sustainable development of facility agriculture in the region. Methods Based on farmer survey data grouped according to yield and efficiency, this study analyzed the resource input, environmental cost, and mitigation potential of plastic-greenhouse tomato production and identified reasonable mitigation measures for tomato production in the Yangtze River Delta. Results The average loss of reactive nitrogen (Nr) in the farmers’ tomato production systems was 96.7 kg N ha −1 ; the N footprint was 1.14 kg N t −1 ; and the Nr emission per unit net profits (Nr NP ) was 7.75 kg N $1000 –1 . There was a large difference in the active nitrogen (Nr) loss and greenhouse gas (GHG) emissions for tomato production among farmers. Compared with the high-yield and high-efficiency (HH) group, Nr loss of the low-yield and low-efficiency (LL) and high-yield and low-efficiency (HL) groups were 60.6% and 80.9% higher, and the GHG emissions of the LL and HL groups were 29.2% and 41.6% higher, respectively. Meanwhile, Nr loss and GHG emissions of the low-yield and high-efficiency (LH) group were 17.5% and 13.4% lower than those of the HH group. Conclusions Based on these findings, reducing the amount of nitrogen applied, using organic alternative methods, returning straw to the field, and reducing irrigation water are the recommended mitigations to reduce the environmental costs of greenhouse vegetable production.

Plastic-covered greenhouse (PCG) farming has been practiced worldwide, particularly in highland areas, for planting fruits and garden plants. Highland areas in south-central Vietnam have been witnessing an expansion of PCG farming in recent decades. For sustainable management of plastic-covered greenhouse farming areas, a proper and continuous monitoring of their spatial patterns is necessary. In this study, we used spaceborne multispectral imagery (Landsat-8 OLI and Sentinel-2 MSI) for automatic detection and mapping of plastic covered greenhouse farming areas in and surrounding areas of Dalat City in Lam Dong province, south-central Vietnam. Unsupervised (K-Means algorithm) and automatic delineation using spectral indices were applied to the Sentinel-2 and Landsat-8 data for mapping plastic-covered greenhouses in Dalat City and surrounding areas. The results were evaluated using field data; automatic spectral index-based mapping of PCGs using Sentinel-2 and Landsat-8 data was found as robust in terms of the overall accuracy. The overall accuracies of PCG maps derived from Sentinel-2 and Landsat-8 data by applying spectral indices were 90.8% and 88.7%, respectively, and those of unsupervised K-Means classification were estimated as 73.2% and 71.7%, respectively. This study estimated that about 2425 ha of plastic-covered greenhouses existed within in Dalat City in 2020.

This study comprehensively analyzed the heat loss and total heat transfer coefficient (U-value) of a single-span experimental plastic greenhouse covered with a double layer of 0.1 mm thick polyethylene. The air temperature and heat flux (W m−2) of the greenhouse components were measured from 18:00 to 06:00, and the energy balance equations under steady-state conditions were determined. The heat flux and U-value of the roof, sides, front and rear, and floor of the greenhouse were determined and compared. The results showed that these values for the roof play an important role in determining the heat load in the greenhouse, and that the average heat transfer through the floor is very small. The average U-value of the greenhouse cover is a comprehensive value which takes the U-values of the roof, sides, and front and rear into account through the use of an area–weighted average method. Finally, an average U-value of 3.69 W m−2 °C −1 was obtained through the analysis of the variations in the U-value, as it is related to the difference in air temperature between the interior and exterior of the greenhouse, as well as to the outdoor wind speed. The relationships between the average U-value and those of the roof, sides, and front and rear of the experimental greenhouse were modeled, and were shown to have a highly linear relationship.

This article investigates the environmental sustainability of plastic nets in agricultural environments based on published experimental data. This article focuses on biodegradable and synthetic plastics used in farms as mulching materials and shade materials/greenhouse covering materials (shade nets and plastic films) to protect plants from pests and extreme weather. The sustainability was determined by three factors, carbon footprint from cradle to the end of life (LCA), durability (resistance to photo-oxidation and high tensile strength), and affordability. The LCA analyses showed that the production of polyethylene (PE) requires less energy and generates low quantities of greenhouse gas equivalents. Beyond the LCA data, biodegradable polymers are sustainable based on biodegradability and compostability, ability to suppress weeds, control soil temperatures, and moisture, and augment fertigation and drip irrigation. However, existing technologies are a limiting factor because lab-based innovations have not been commercialized. In addition, industrial production of shade nets, plastic greenhouse covers, and mulching materials are limited to synthetic plastics. The bio-based plastic materials are sustainable based on biodegradability, and resistant to photo-oxidation. The resistance to UV degradation is an essential property because solar radiation cleaves C-C bonds, which in turn impact the mechanical strength of the materials. In brief, the sustainability of plastics in farms is influenced by LCA data, mechanical and optical properties, and performance relative to other materials.

The fast and accurate extraction of plastic greenhouses over large areas is important for environmental and agricultural management. Traditional spectral index methods and object-based methods can suffer from poor transferability or high computational costs. Current deep learning-based algorithms are seldom specifically aimed at extracting plastic greenhouses at large scales. To extract plastic greenhouses at large scales with high accuracy, this study proposed a new deep learning-based network, U-FDS Net, specifically for plastic greenhouse extraction over large areas. U-FDS Net combines full-scale dense connections and adaptive deep supervision and has strong future fusion capabilities, allowing more accurate extraction results. To test the extraction accuracy, this study compiled new greenhouse datasets covering Beijing and Shandong with a total number of more than 12,000 image samples. The results showed that the proposed U-FDS net is particularly suitable for complex backgrounds and reducing false positive conditions for nongreenhouse ground objects, with the highest mIoU (mean intersection over union) an increase of ~2%. This study provides a high-performance method for plastic greenhouse extraction to enable environmental management, pollution control and agricultural plans.

Plastic films used for crop protection have reached notable consumption all over Europe, as well as in the rest of the world. This phenomenon however poses a serious environmental problem connected with the impact on the sustainability of agricultural production and relevant plastic footprint. Mechanical recycling of agricultural plastics is a common technique, but limited by many factors, as the loss of mechanical properties of plastic film. This phenomenon, due to its ageing after being exposed to natural weather conditions, plays a crucial role, especially when aggravated by contamination with agrochemicals ordinarily used for crop health and pest management. This article reports the result of some laboratory tests on agricultural plastic film, artificially aged for different periods and contaminated with two different agrochemicals (anti-aphid or fungicide). These results show that the impact of agrochemicals on plastic film is considerable, since it worsens the ageing process of the plastic film, conducting a more rapid reduction in its mechanical properties—mostly, a faster reduction in the elongation at break below 50% of the corresponding value of the virgin plastic film. This phenomenon, other than reducing the working life of the plastic film, gives it a low potential for being transformed into a closed-loop recycled material when entering the recycling stage. The increase in the value of the detected Carbonyl Index (CI) confirms the tendency of the material to degrade rapidly when in contact with agrochemicals, hence indicating that it may be impossible to mechanically recycle it.