Plastic Greenhouse Research Articles

Analysis of Wind Pressure Coefficients for Single-Span Arched Plastic Greenhouses Located in a Valley Region Using CFD

The wind pressure coefficient is essential for calculating the wind loads on greenhouses. The wind pressure on single-span arched greenhouses built in valleys differs from those in plain regions. To promote our understanding of wind characteristics and ensure the structural safety of greenhouses in valley areas, an analysis of the distribution law of wind pressure on greenhouses is required. Firstly, we carried out a survey on greenhouse distribution and undulate terrain distribution near greenhouses in Tibet and measured the air density in Lhasa, Tibet. Then, employing the validated realizable k-ε turbulence model and the verification of grid independence, the wind pressure on greenhouses with different greenhouse azimuths was investigated. According to the survey results, values, such as the distance between the greenhouse and the mountain in addition to the greenhouse azimuth, were also obtained for calculating the wind pressure on greenhouses placed in valleys. A calculation model considering the relationship between the mountain distance and the wind pressure coefficient is proposed, whose results fit well with the results from computational fluid dynamics. The relative errors between the two different results are within 15%. Research shows that there is a canyon wind effect in the valley area, and its effect on wind pressure should be considered in greenhouse design. This research is valuable for the design of plastic greenhouses built in Tibet or other valley regions.

First report of potato virus S and potato virus Y in tomatoes from Croatia.

Potato virus Y (PVY, genus Potyvirus) is an economically important aphid-transmissible virus with a very wide host range reported in many tomato-growing areas (Rivarez et al. 2021). Potato virus S (PVS, genus Carlavirus) has a limited host range (Lin et al. 2014) and occurs in tomato (Predajňa et al. 2017), mostly in mixed infections with other viruses. In 2021, greenhouse tomatoes from Vidovec (46° 17' 3.4'' N, 16° 15' 37.0'' E) in the northwestern and Sedlarica (45° 54' 23.0'' N, 17° 12' 0.5'' E) in the eastern regions of Croatia were surveyed for virus-like diseases. In total, 30 plants were sampled (12 from Vidovec and 18 from Sedlarica) showing symptoms of mild mottling, leaf rugosity and mild bronzing followed by leaf necroses later in the season. Nucleic acids were extracted from leaves by adapted CTAB procedure (Murray and Thompson 1980) and DNase treated. Four representative samples from Vidovec and four from Sedlarica were pooled for high throughput sequencing (HTS). After rRNA depletion (RiboMinus™ Plant Kit for RNA-Seq, Invitrogen) and polyA tailing, two location specific libraries (PCR-cDNA sequencing kit, Oxford Nanopore Technologies) were prepared for nanopore HTS on MinION Mk1C device. From Vidovec samples, 459,285 raw reads (mean length 354 nt) were obtained and 206,718 (mean length 446 nt) from Sedlarica and mapped (Minimap2, v.2.17) against Kraken2 viral genome sequences database (https://benlangmead.github.io/aws-indexes/k2). The number of reads mapped to PVS genome was 1004 from Vidovec (coverage depth 1.56) and those mapped to PVY genome were 781 (coverage depth 0.99) and 57 (coverage depth 1), from Vidovec and Sedlarica, respectively. The PVS complete consensus genome from Vidovec (ON468562, 8485 nt) had 99.09% nucleotide identity (BLASTn) to a potato isolate from the Netherlands (MF418030). The PVY consensus genome sequences from Vidovec (ON505007, 9698 nt) and Sedlarica (ON505008, 9698 nt) had respectively 98.37% and 98.48% identities to a tomato isolate from Slovakia (MW685827). Reverse transcription polymerase chain reaction (RT-PCR) was performed for all 30 samples and amplicons were Sanger sequenced, with primers PVS-7773F/PVS-3'endR for a 720 nt PVS genome portion spanning the 3'-part of the CP and a complete 11K gene (Lin et al. 2014) and PVY-2F/2R primers for a 510 nt portion of PVY CP gene (Aramburu et al. 2006). Only one tomato out of 12 ('Borana') from Vidovec harbored PVS in the mixed infection with PVY. Two additional tomatoes from Vidovec and two from Sedlarica were infected solely by PVY. Amplicon sequences of PVS (ON651427) and PVY (ON707000-4, ON734067-8) had 100% identity with the HTS assembled sequences. The PVS isolate from Croatia grouped with PVSO (ordinary) strain in phylogenetic analysis and the PVY isolates from both sites grouped with the PVY-NTN strain (Cox and Jones 2010). Although PVY is considered to be widespread in tomato (Nikolić et al. 2018; Rivarez et al. 2021), this is its first report from Croatia. PVS, newly reported from Croatia here, is probably not associated with the symptoms recorded because the same symptomatology was observed in the singly and mixed infected 'Borana' tomato plants. The occurrence of PVY in the geographically distant (100 km apart) Vidovec and Sedlarica, suggests that it is widespread in the continental Croatia where tomatoes are commercially grown in plastic greenhouses. Further analyses are needed to elucidate PVY and PVS epidemiology and impact on the local tomato production.

Occupational Exposure to Pesticides as a Risk Factor for Sleep Disorders.

Inadequate sleep has been linked to a variety of impairments in bodily functions, including endocrine, metabolic, higher cortical function, and neurological disorders. For this reason, the aim of this study was to analyze the link between occupational pesticide exposure and sleep health among farmers in Almeria. A cross-sectional study was conducted among a population living on the coast of Almeria (southeastern Spain), where about 33,321 hectares of land are used for intensive agriculture in plastic greenhouses. A total of 380 individuals participated in the study: 189 greenhouse workers and 191 control subjects. The participants were contacted during their annual scheduled occupational health survey. Data on sleep disturbances were collected using the Spanish version of the Oviedo Sleep Questionnaire. Agricultural workers were found to be at a significantly higher risk of insomnia, especially among those who did not wear protective gloves (OR = 3.12; 95% C.I. = 1.93-3.85; p = 0.04) or masks (OR = 2.43; 95% C.I. = 1.19-4.96; p = 0.01). The highest risk of insomnia related to pesticide applicators was observed in those who did not wear a mask (OR = 4.19; 95% C.I. = 1.30-13.50; p = 0.01) or goggles (OR = 4.61; 95% C.I. = 1.38-10.40; p = 0.01). This study supports previous findings indicating an increased risk of sleep disorder in agricultural workers exposed to pesticides at work.

Multitemporal greenhouse mapping for high-resolution remote sensing imagery based on an improved YOLOX

Plastic greenhouses (PGs), as safeguard agricultural facilities, have changed the cultivation structure of agriculture, to a certain extent, and can seriously impact the environment. Exploring the temporal characteristics of greenhouses in terms of quantity and area is significant for sustainable agricultural development and environmental protection. Pixel or object-based large-scale greenhouse mapping has difficulty meeting the demand for the simultaneous extraction of greenhouse quantity and area. Multibranch task model can provide the number and area information of greenhouse. However, there are various labeling methods and model between different branches, which lead to the deviation between quantity and area results. This paper proposes a model that is based on improved you only look once X (YOLOX) and kullback–leibler divergence (KLD), called YOLOX and KLD plus (YXLD + ), to obtain spatiotemporally consistent greenhouse mapping. The new model still has stable performance in dense scenes, with a 5.7 % improvement in average precision compared to BBAVectors. Finally, a multitemporal greenhouse map of Zhoukou City was obtained using imagery provided by Google Earth (GE). Overall, the distribution of greenhouses in Zhoukou City remained stable between 2012 and 2017. However, the number and area of greenhouses in local areas has increased rapidly in the past five years, with the number of greenhouses increasing by 47.08 % and the area expanding by 41.38 %. Greenhouses' distribution and changing characteristics concentrate on the gently sloping areas from the northwest to the southeast. These results provide an objective perspective on the development of the local agricultural cultivation structure, which is of significant importance for the promotion of agricultural modernization.

USING YOLOV5 TO DETECT PLASTIC GREENHOUSES IN MOROCCO

Abstract. Globally, Increasing greenhouse production is causing producing environmental issues. Monitoring the number and determining the locations of greenhouses are essential for the modern agricultural land management. The aim of this study was to detect plastic greenhouses using remote sensing data and the YOLOv5 CNN-based object detection algorithm. In the process, 426 images of plastic greenhouses were manually downloaded from Google and Mohammed 6 satellites and were divided into three datasets, training (63%), validation (15%), and testing (22%). Plastic greenhouse images in the training and validation sets were manually labeled, with the training set being used to train the YOLO-V5 Model. Throughout the training, the validation dataset was used to evaluate how well the network performed. According to the performance results the system reached its highest level of accuracy at epoch 71, with a relatively brief training time of 40 minutes, The model’s average precision was 84.1 percent, Using satellite images. In detecting plastic greenhouses, YOLOv5 can deliver exceptional accuracy and computational performance.

Microplastics in terrestrial ecosystem: Sources and migration in soil environment

Plastics, especially microplastics in soils, are considered a severe environmental issue worldwide. However, globally, the main research focus is on microplastic pollution in the marine environment, the microplastic pollution on soils and sediments remains on the sideline so far. But the fact is that microplastics are omnipresent in terrestrial systems in the form of microbeads in industrial systems and in sewage sludge. Their presence in agricultural soils and sediments is enormously increased due to plastic mulching, plastic greenhouses and compost and extensive use of controlled release fertilizers. Therefore, this review outlines the global scenario regarding plastics and microplastics production, consumption, and possible pathways of penetration into the soil environment. Various mechanisms to restrict and manage the pathways of plastics and microplastics into the soil environment are also discussed. This review also focuses on the challenges and limitations on the use of plastic alternates such as bioplastics and oxo plastics. Also, the knowledge gaps on the source of microplastics in the environment and their deleterious effects on properties of soil, soil health and focused light on their soil trophic transfer in food chains via plants. This review provides a detailed insight on the management and possible control measures to alleviate the potential risk caused by microplastics pollution in the soil environment and the overall ecosystem's health. In spite of the occurrence and fate of microplastics on terrestrial environment, knowledge gaps and challenges for tackling this contamination are also explored which facilitates the policy makers to develop regulatory measures towards the containment of microplastics in living ecosystem.

Pixel–Scene–Pixel–Object Sample Transferring: A Labor-Free Approach for High-Resolution Plastic Greenhouse Mapping

As an important agriculture technique, plastic greenhouse (PG) has been widely used to increase crop yield and improve food security status in the world. The high-resolution spatial information of PG is of great significance to precise agricultural management and quantitative environmental assessment. Many studies have examined the role that remote sensing technology could play in mapping and monitoring PG coverage. However, these methods, which employ either the traditional machine learning algorithms or the deep learning models, depend on massive manually labeled samples. To address this problem, this paper proposes a new cross-scale sample transferring method to generate high-resolution samples for automated PG mapping. The proposed method aims to transfer reliable label information from Sentinel-2 images (10-m) to high-resolution images (0.2-m) in a pixel-scene-pixel-object (PSPO) transferring process. In the proposed PG mapping workflow, the low-resolution label information of PG/non-PG can be obtained from an advanced plastic greenhouse index (APGI) which is calculated in Sentinel-2 images, and then the label information is transferred to the corresponding high-resolution images using the proposed PSPO transferring method. Finally, the transferred high-resolution samples are used to train the deep semantic segmentation model and produce PG mapping results. The whole process is labor-free which requires no manually labeled samples. The experimental results on three collected datasets show that the proposed approach can automatically generate accurate and reliable high-resolution samples, and the final PG mapping results can achieve an OA (overall accuracy) of 89.52% ~ 97.65% and F1 score of 84.13% ~ 94.03%, which is comparable to the fully supervised semantic segmentation model.

Growth of tomato and cucumber seedlings under different light environments and their development after transplanting.

Selecting suitable light conditions according to the plant growth characteristics is one of the important approaches to cultivating high-quality vegetable seedlings. To determine the more favorable LED light conditions for producing high-quality tomato and cucumber seedlings in plant factories with artificial light (PFALS), the growth characteristics of tomato and cucumber seedlings under seven LED light environments (CK, B, UV-A, FR, B+UV-A, UV-A+FR, and B+FR) and the development of these seedlings after transplanting into a plastic greenhouse were investigated. The results showed that the seedling height and hypocotyl length increased in treatments with far-red light supplementation (FR, UV-A+FR, and B+FR), but decreased in the B treatment, in both varieties. The seedling index of tomato seedlings increased in the B+UV-A treatment, while that of cucumber seedlings increased in the FR treatment. After transplanting into a plastic greenhouse, tomato plants that radiated with UV-A had greater flower numbers on the 15th day after transplanting. In cucumber plants of the FR treatment, the flowering time was significantly delayed, and the female flower exhibited at a lower node position. By using a comprehensive scoring analysis of all detected indicators, light environments with UV-A and FR were more beneficial for improving the overall quality of tomato and cucumber seedlings, respectively.

Study of PLA-based Wood-Plastic Composites

In order to cope with the environmental problems of plastic pollution and greenhouse gas emission, the development and utilization of environmentally friendly materials is urgent. Polylactic acid (PLA) is a completely degradable thermoplastic aliphatic polyester, but the high cost and poor toughness of PLA limit its wide application. PLA-based wood-plastic composites (WPC), prepared by laminating PLA with wood fibers, can reduce production costs and compensate for the deficiencies of PLA mechanical properties, while still retaining biodegradability. The synthesis of PLA, the preparation of PLA-based WPC, and the performance enhancement achieved by different wood fibers prepared WPC are presented. It is hoped that this will provide guidance for the early promotion of PLA-based WPCs.

Management of Root-Knot Nematode with Non-Chemical Methods for Sustainable Production of Cucumber under Protected Cultivation

The multi-faceted benefits of growing crops under protected cultivation are gradually establishing it as a promising technology for vegetable cultivation in India. However, the adoption of successive cropping patterns in soil-based closed structures is leading to the buildup of soil-borne pathogens and pests, which are becoming a major hindrance to the sustainable production of these crops, particularly in the northern plains. Root-knot nematodes (RKNs) are a critical threat to protected cultivation and farmers are required to contribute a significant amount of time and money for their management. To reduce the overdependence of chemicals, the present study explored the potential of plant-based by-products as amendments for the management of RKN in cucumbers grown under a plastic greenhouse. A pot trial was conducted to assess the efficacy of different plant-based amendments against nematodes in cucumber plants. The pot trial results revealed that the application of mustard cake (MC) and neem cake (NC) at 1 t ha−1 either alone or as a combined application with farmyard manure (FYM) of 2.5 t ha−1 was effective against RKN infestation, reflecting the improved plant growth parameters of cucumber. Based on the results of the pot trials, treatments with plant-based amendments and FYM i.e., T1: MC 1 t ha−1; T2: NC 1 t ha−1; T3: FYM 2.5 t ha−1; T4: MC 1 t ha−1 + NC 1 t ha−1 + FYM 2.5 t ha−1, along with the treated check carbofuran 3 G 2 kg (a.i.) ha−1 (T5) and untreated check (T6), were evaluated in multi-locational field trials. The results revealed that the combined application of MC 1 t ha−1 + NC 1 tha−1 + FYM 2.5 t ha−1 exhibited promising results in decreasing RKN infestation (56–58%) in all of the three RKN-infested polyhouses, with significantly enhanced yields at all of the three locations. Soil organic carbon also increased significantly in the amended plots, indicating improved soil health. The results of the present work hold good promise for the management of RKN in the protected cultivation of cucumber with an environment friendly approach, along with the additional incentives of improved soil health.

Farklı Vermikompost Dozlarının Kıvırcuk Marulda (Lactuca sativa L. var. crispa) Büyüme, Kalite ve Element İçerikleri Üzerine Etkisi

This study was conducted to determine the effects of different vermicompost doses on plant growth, quality properties and element contents in curly lettuce (Lactuca sativa L. var. crispa). The research was carried out in pots under plastic greenhouse conditions in Karabük province. In the study, 6 applications as 4 different doses of vermicompost (V), chemical fertilizer (CF) and control were examined. The applications were as follows: 1) Control (100% soil), 2) V1 (97.5% soil + 2.5% vermicompost, w/w), 3) V2 (95% soil + 5% vermicompost, w/w), 4) V3 (90% soil + 10% vermicompost, w/w), 5) V4 (80% soil + 20% vermicompost, w/w) and 6) CF (100% soil + chemical fertilizer). The experiment was established in completely randomized design with 3 replications. According to the research findings, vermicompost applications significantly increased plant height, plant fresh weight, plant dry weight, number of marketable leaves, chlorophyll, nitrogen, phosphorus, potassium, magnesium, calcium, sodium, iron, copper, and zinc contents of the plant compared with the control. When compared to the control, V1 application increased plant fresh weight by 13.25% and phosphorus content by 44.07%; V2 application increased potassium content by 24.29%; V3 application increased plant height by 13.77%, chlorophyll content by 22.30% and nitrogen content by 53.23%; V4 application increased magnesium content by 48.46%, calcium content by 14.36% and zinc content by 16.19%. It was detected that vermicompost had positive effects on plant growth, quality properties and element contents in curly lettuce. As a result, vermicompost can be used successfully as an alternative organic fertilizer for sustainable agriculture in curly lettuce cultivation.

Photothermal performance of plastic greenhouse embedded with phase change materials in translucent envelopes: A dynamic experimental study

An adaptable façade can be a translucent envelope with phase change materials (PTE) integrated into the typical plastic greenhouses to respond to dynamic changes in temperature and daylight. Unlike opaque constructions integrated with phase change materials (PCM), PTE can act as a governor to coordinate light and thermal performance. This paper conducts an experimental investigation on the photothermal performance of plastic greenhouses integrating PTEs. The integration of PTEs requires an evaluation between the different melting temperatures of PCM (PW-18#, PW-25#, PW-28#) and seasons (transition, autumn, winter) rationally design plastic greenhouse featuring tunable indoor daylight and air temperature. The cross-seasonal analysis and thermal environment evaluation are also carried out. The results show that plastic greenhouses with PTEs substantially tune thermal energy storage/release and attenuate indoor daylight. In a separate seasonal investigation, it is observed that PTEs with PW-28# produced adjustable average air temperatures of 26.4 °C and lowered daylight levels of 10,245 lx, making them desirable during transitional seasons. Likewise, PTEs with low melting temperatures are advantageous because of the reduced outside temperature and daylight. According to the cross-seasonal investigation, PTEs with high melting temperatures find it difficult to sustain long-term operation because of the inadequate degree of phase transition cycle. PTEs have the advantage of rebuilding the internal thermal environment and increasing the upper layer's distance from the ground by 2.4 °C. Finding the best states to build a low-cost, easily replaceable passive heating system for plastic greenhouses can be made easier with the help of the understanding of the built-in PTEs.

Mitigation of Chilling Stress by Ozone Pretreatment and Acclimation of Sweet Pepper Grown under Unheated Greenhouse Conditions

Ozone is an important air pollutant that causes many challenges for human health, such as lung diseases. The negative impacts of exogenous ozone on cultivated plants have been discussed in several publications, but the positive impacts are less investigated. The current study is an attempt to answer the following question: is there any positive contribution of ozone pretreatment in growing plants under stress? Plants grown in unheated plastic greenhouses suffer from cold stress during the winter when the temperature drops to 5–10 °C. This stress can also be enhanced under saline soil conditions in arid regions. Treatments involving different ozone application methods (seed priming and seedling foliar application) and cold pretreatment (4 °C for 36 h) were compared with untreated controls of two sweet pepper hybrids (Zidenka and Lirica) in an unheated plastic greenhouse. In general, the Lirica hybrid outperformed the Zidenka hybrid in growth and fruit yield and showed good adaptation to cold stress resulting from ozone treatment through foliar application on seedlings. Moreover, cold treatment was associated with higher values of the studied parameters compared to the control (untreated). A concentration of 20 ppm of ozone in the first season and as 30 ppm of ozone in the second season increased plant leaf area, proline content, and APX activity, all of which improved the plant’s defense mechanisms against cold stress. These benefits contributed to high fruit sets; early, total, and marketable fruit yields; and fruit quality under cold stress. The highest yield (16.52 kg m−2) was attained with 30 ppm ozone applied as a seedling spray, compared with 10.07 kg m−2 in the control. Therefore, the foliar application of ozone up to 30 ppm can be recommended for sweet pepper hybrids of Lirica under unheated plastic greenhouse conditions. Further investigations are needed to study the interaction of combined ozone and cold stress, as well as various levels of soil salinity.

Spatial and temporal evolution and greenhouse gas emissions of China's agricultural plastic greenhouses

The rapid development of the use of agricultural plastic greenhouses in China in recent years has played an important role in the generation of economic benefits from agriculture. However, it has also led to severe negative environmental impacts. Thus, it is necessary to explore the spatial and temporal evolution of agricultural plastic greenhouses in China as well as their environmental impacts so as to obtain a deeper understanding of agricultural intensification and the sustainable development of the facility agriculture industry. To this end, this study analyzed the spatial and temporal evolution characteristics of agricultural plastic greenhouses and their greenhouse gas emissions within the 2000–2020 period based on the extraction of the spatial distribution of greenhouses in China in 2000, 2010, and 2020. Landsat imagery and statistical data combined with the random forest classification method as well as life cycle analysis, were used in this study. The results obtained showed that: (1) Within the 2000–2020 period, the area covered by agricultural plastic greenhouses in China expanded from 1594.66 to 11,838.77 km2, with most of the greenhouses predominantly distributed in the North China Plain. (2) The increase in total greenhouse gas emissions between 2000 and 2010 was mainly due to the expansion of agricultural plastic greenhouse and an increase in agricultural material inputs, whereas the increase between 2010 and 2020 was mainly due to the expansion of agricultural plastic greenhouse. (3) Greenhouse gas emissions from nitrogenous fertilizers and greenhouse construction materials accounted for 45 % and 36 % of the total greenhouse gas emissions, respectively. These findings are of great significance as they enhance understanding regarding land intensification development and its accompanying environmental impacts in China.

Microplastics in agroecosystems: A review of effects on soil biota and key soil functions

AbstractContamination of soils in agroecosystems with microplastics (MPs) is of increasing concern. The contamination of the environment/farmland soils with MPs (1 µm to 5 mm sized particles) and nanoplastics (NPs; <1 µm sized particles) is causing numerous effects on ecological soil functions and human health. MPs enter the soil via several sources, either from intentional plastic use (e.g., plastic mulch, plastic greenhouses, plastic‐coated products) or indirectly from the input of sewage sludge, compost, or irrigation water that is contaminated with plastic. Once in the soil, plastic debris can have various impacts such as changes in soil functions and physicochemical properties and it affects soil organisms due to its toxic behavior. This review paper describes the different effects of plastic waste to understand the consequences for agricultural productivity. Furthermore, we identify knowledge gaps and highlight the required approaches, indicating future research directions on sources, transport, and fate of MPs in soils to improve our understanding of various unspecified abiotic and biotic impacts of MP pollution in agroecosystems.

Evaluation on near infrared-reflective diffuse coating for muskmelon production in simple plastic greenhouse during summer season

ISHS XXXI International Horticultural Congress (IHC2022): International Symposium on Integrative Approaches to Product Quality in Fruits and Vegetables Evaluation on near infrared-reflective diffuse coating for muskmelon production in simple plastic greenhouse during summer season

Effects of Uplift Resistance on Continuous-Pipe-Foundation of Single-Span Plastic Greenhouse by Steel Plate Pipe Connector

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.

Effects of Atmospheric Correction and Image Enhancement on Effective Plastic Greenhouse Segments Based on a Semi-Automatic Extraction Method

To improve the multi-resolution segmentation (MRS) quality of plastic greenhouses (PGs) in GaoFen-2 (GF-2) images, the effects of atmospheric correction and image enhancement on effective PG segments (EPGSs) were evaluated. A new semi-automatic method was also proposed to extract EPGSs in an accurate and efficient way. Firstly, GF-2 images were preprocessed via atmospheric correction, orthographical correction, registration, fusion, linear compression, or spatial filtering, and, then, boundary-removed point samples with adjustable density were made based on reference polygons by taking advantage of the characteristics of chessboard segmentation. Subsequently, the point samples were used to quickly and accurately extract segments containing 70% or greater of PG pixels in each MRS result. Finally, the extracted EPGSs were compared and analyzed via intersection over union (IoU), over-segmentation index (OSI), under-segmentation index (USI), error index of total area (ETA), and composite error index (CEI). The experimental results show that, along with the change in control variables, the optimal scale parameter, time of segmentation, IoU, OSI, USI, and CEI all showed strong changing trends, with the values of ETA all close to 0. Furthermore, compared with the control group, all the CEIs of the EPGSs extracted from those corrected and enhanced images resulted in lower values, and an optimal CEI involved linearly compressing the DN value of the atmospheric-corrected fusion image to 0–255, and then using Fast Fourier Transform and a circular low-pass filter with a radius of 800 pixels to filter from the spatial frequency domain; in this case, the CEI had a minimum value of 0.159. The results of this study indicate that the 70% design in the experiment is a reasonable pixel ratio to determine the EPGSs, and the OSI-USI-ETA-CEI pattern can be more effective than IoU when it is needed to evaluate the quality of EPGSs. Moreover, taking into consideration heterogeneity and target characteristics, atmospheric correction and image enhancement prior to MRS can improve the quality of EPGSs.

Response of rhizosphere microbial community of Chinese chives under different fertilization treatments.

Soil microorganisms play an irreplaceable role in agricultural production, however, an understanding of response of soil microorganisms to slow-release and common fertilizer applications is limited. In this study, different amounts of slow- release fertilizer were used to overwintering Chinese chives growing area in a plastic greenhouse to investigate the effects of on rhizosphere soil physicochemical properties and soil microbial communities (bacteria and fungi) of Chinese chives. The result displayed that application of slow-release fertilizer significantly improved soil nutrients, soil enzyme activity, and soil microbial community structure and diversity compared to conventional fertilizer application. Compared with T1 treatment, the content of total nitrogen (TN) and available phosphorus (AP), and the SU-E activity in the soil of T2 (NPK: 62.8 kg · 667 m-2) increased by 42.58%, 16.67%, and 9.70%, respectively, showing the best effects. In addition, soil bacterial diversity index and soil microbial community structure were improved as indicated by increased relative abundance of each species, such as Byssovorax, Sandaracinus, and Cellvibrio. Oppositely, the both soil fungal diversity and the number of species decreased after fertilizationthe relative abundance of Ascomycota increased in each fertilization treatment detected by ITS sequencing. Further, the relative abundance of pathogenic fungi such as Pezizomycetes, Cantharellales, and Pleosporales decreased in the T2 treatment. Principal Coordinates Analysis (PCoA) showed that both the amount of fertilizer applied and the type of fertilizer applied affected the soil microbial community structure. RDA evidenced that soil bacteria, Proteobacteria and Gemmatimonadetes, were closely correlated with soil AN, SOM, and AK. Acidobacteria were closely correlated with soil pH, TN, and AP. Ascomycota was closely correlated with soil pH and TN. In conclusion, the application of slow-release fertilizers and reduced fertilizer applicationcould improve soil physical and chemical properties as well as soil microbial community structure and diversity, contributing to sustainable soil development. The recommended fertilization rate for overwintering Chinese chives is NPK: 62.8 kg · 667 m-2.

Influence of the Diffusivity and Transmittance of a Plastic Greenhouse Cover on the Development of Fungal Diseases in a Cucumber Crop

Mediterranean greenhouses are usually covered by plastic materials (films); these films allow light to pass through them, modifying some of their characteristics. The properties of the plastic cover influence the development of greenhouse crops. In addition, it can influence the stresses that the plants endure and the development of fungal diseases in the crop. The aim of this study is to analyze the effect that an experimental film cover, with high transmittance and high light diffusivity, produces on the development of fungal diseases on a cucumber crop (Cucumis sativus L.). Two different film covers were compared: (i) commercial film (transmittance of 85%; diffusivity of 60%); and (ii) experimental film (transmittance of 90%; diffusivity of 55%). The study was carried out across two autumn–winter crop cycles in a multi-span greenhouse divided into two isolated sectors. Three fungal diseases caused the main damage to the cucumber crop: downy mildew (Pseudoperonospora cubensis), powdery mildew (Sphaerotheca fuliginia) and gummy stem blight (Didymella bryoniae). In the case of powdery mildew, a greater severity in the sector was observed with the commercial film in comparison with the sector with the experimental film, with significant statistical differences between the two sectors in both crop cycles. Downy mildew and gummy stem blight were fungal diseases with less presence than downy mildew, and a greater presence of these two fungal diseases in the sector with the commercial film was also observed in both crop cycles.