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  • 1
    Publication Date: 2019
    Description: The present work analyses the traditional method of applying whitening products on Mediterranean greenhouses. Four commercial whitening products (agricultural solar protectors, ASPs), applied at four doses, were compared with a non-whitened cover. The traditional product “Blanco de España” with 99% calcium carbonate (CaCO3) and other three products with 97% CaCO3 that incorporate adhesives were tested. The use of adhesives in ASP did not influence the effect of the different products on the inside temperature, and at the same dose all four products show a similar behaviour. The findings support the maximum dose recommended by other authors of 0.50 kg L−1 (50/100), above which the transmissivity of the greenhouse cover decreases by over 50%. The effect of ASP on the transmissivity of the cover depends principally on the dose applied, but also on the climatic conditions (solar radiation, cloud cover, etc.) and on the time of year (solar elevation). The habitual use of a constant dose throughout the year does not seem to be the most adequate. Recommended doses should vary according to the time of year and the desired degree of transmissivity reduction. The adhesive components are shown to provide a high degree of protection against heavy rain. The study recommends a standardised method of ASP application, establishing a method that allows the grower to verify the concentration of the product that will remain on the greenhouse cover.
    Print ISSN: 1661-7827
    Electronic ISSN: 1660-4601
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Published by MDPI
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  • 2
    Publication Date: 2019
    Description: The aim of this work was to analyze the influence of the salinity of the nutrient solution on the transpiration and growth of Cordyline fruticosa var. “Red Edge” plants. A specific irrigation management model was calibrated with the experimental data. An experiment was performed with four treatments. These treatments consisted of the application of four nutrient solutions with different electrical conductivity (ECw) levels ranging from 1.5 dS m−1 (control treatment) to 4.5 dS m−1. The results showed that day-time transpiration decreases when salt concentration in the nutrient solution increases. The transpiration of the plant in the control treatment was modelled by applying a combination method while the effect of the salinity of the nutrient solution was modelled by deriving a saline stress coefficient from the experimental data. The results showed that significant reductions in plant transpiration were observed for increasing values of ECw. The crop development and yield were also affected by the increasing salinity of the nutrient solution. A relationship between the ECw and the relative crop yield was derived.
    Electronic ISSN: 2071-1050
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI
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  • 3
    Publication Date: 2018
    Description: The Cape of Gata region (southeast Spain) allocates the thermo-haline Almeria–Oran front (AOF), which separates two biogeographical zones, with a very irregular bathymetry, consisting of two canyons and seamounts in an area of 100 × 100 km. An interdisciplinary oceanographic sampling strategy allowed us to solve mesoscale processes including current–bathymetry interactions. Subsurface fertilizing processes and elevated chlorophyll a concentrations were found at the front, seamount, and submarine canyons, turning an apparently oligotrophic area into a rich one. According to a horizontal tracking simulation, the deep chlorophyll maximum (DCM) at the front is located above the pycnocline and travels fast offshore, transporting productivity from the fertilization process quickly from the region. The DCM at the seamount, in contrast, develops below the pycnocline and remains for almost three weeks in this area. In spite of the coastal marine protected areas (MPAs), a high surface nitrate concentration plume with its origin in a small coastal area without any protection was detected. Local circulation patterns and bathymetry–current interactions provide elevated productivity in surface water which is vertically connected to deep-sea fauna via the daily vertical migration of zooplankton, suggesting elevated biodiversity on the seamount and canyons of the area studied. Based on these results, and considering the presence of coastal MPAs and a Coastal Area Management Program, future studies on benthic fauna, an enlargement of coastal MPAs, and a transboundary land–deep-sea management program are suggested.
    Electronic ISSN: 2073-4441
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI
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  • 4
    Publication Date: 2019
    Description: The present work analyses the natural ventilation of a multi-span greenhouse with one roof vent and two side vents by means of sonic anemometry. Opening the roof vent to windward, one side vent to leeward, and the other side vents to windward (this last vent obstructed by another greenhouse), causes opposing thermal GT (m3 s−1) and wind effects Gw (m3 s−1), as outside air entering the greenhouse through the roof vent circulates downward, contrary to natural convection due to the thermal effect. In our case, the ventilation rate RM (h−1) in a naturally ventilated greenhouse fits a second order polynomial with wind velocity uo (RM = 0.37 uo2 + 0.03 uo + 0.75; R2 = 0.99). The opposing wind and thermal effects mean that ventilation models based on Bernoulli’s equation must be modified in order to add or subtract their effects accordingly—Model 1, in which the flow is driven by the sum of two independent pressure fields G M 1 = | G T 2 ± G w 2 | , or Model 2, in which the flow is driven by the sum of two independent fluxes G M 2 = | G T ± G w | . A linear relationship has been obtained, which allows us to estimate the discharge coefficient of the side vents (CdVS) and roof vent (CdWR) as a function of uo [CdVS = 0.028 uo + 0.028 (R2 = 0.92); CdWR = 0.036 uo + 0.040 (R2 = 0.96)]. The wind effect coefficient Cw was determined by applying models M1 and M2 proved not to remain constant for the different experiments, but varied according to the ratio uo/∆Tio0.5 or δ [CwM1 = exp(−2.693 + 1.160/δ) (R2 = 0.94); CwM2 = exp(−2.128 + 1.264/δ) (R2 = 0.98)].
    Electronic ISSN: 2073-4395
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by MDPI
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