Polyethylene Cover Research Articles

Colored polyethylene soil covers and grafting effects on cucumber flowering and yield

Cucumber (Cucumis sativus L.) is one of the most cultivated vegetable crops in plastic greenhouses in Brazil because of the short cycle and its high economic value in off-season harvests. To better understand this management technique the effect of different colored polyethylene soil covers was evaluated in relation to flowering and yield of the hybrid cucumber 'Yoshinari' grafted or not on the hybrid squash 'Ikky'. The polyethylene cover colors were black, white on black and green plus a control without cover. Covered but not grafted crops had a more uniform flowering distribution. The number of flowers was greater for the white/black grafted treatment. All the polyethylene covers favored flowering for the non grafted plants. Grafting reduced flowering for the black or green polyethylene covers treatments. The fruit set increased with the use of polyethylene cover but was not influenced by grafting. The uniform distribution of flowering remained during fruiting only for grafted plants and soil covered with black or green polyethylene. Both polyethylene cover and grafting favored early harvesting. The 'Yoshinari'/'Ikky' graft caused taller plants but fruit were thicker and smaller and did not meet the commercial standard. The best quality fruit and highest yields were obtained in the black and white/black treatments, without grafting.

Integrated Control of Black Rot Disease of Wasabi, Caused by Phoma Wasabiae

Soaking with difenoconazole, thiabendazole, benomyl, and polyoxin eliminated the pathogen as an initial inoculum source in rhizome-tillers and root-plantlets of wasabi. The effective period was 2, 4, 8, and 10h, respectively, for difenoconazole, thiabendazole, benomyl, and polyoxin. Because thiabendazole and difenoconazole caused injury to wasabi tillers, only benomyl was used to control disease in tillers in the field. When plots were covered with PE sheets, leaf spot disease of wasabi was significantly reduced. The average disease incidence of black rot was reduced from 90% to 5.9%. The pathogen was effectively prevented by benomyl from spreading from the parent rhizomes to tillers in the field. Treating wasabi tillers only with benomyl, however, did not significantly reduce the disease incidence on wasabi leaves or petioles. In contrast, the tillers from rhizomes treated with benomyl and covered with a polyethylene sheet on the cultivated plot significantly reduced the disease severity on wasabi rhizomes, petioles and leaves. The treatments reduced disease severity from 75% to 12.5% in rhizomes, from 73.5% to 37.5% on petioles, and from 72.6% to 33.5% on leaves of wasabi. The results of this study suggest that using pathogen-free plantlets and preventing secondary infection with polyethylene cover could be effective in controlling black rot disease of wasabi in the field.

Factors Associated with Foliar Disease of Staked Fresh Market Tomatoes Grown Under Differing Bed Strategies

The use of mulch or compost to reduce foliar disease in fresh market tomato could reduce fungicide use. Between 1997 and 1999, foliar disease was monitored in tomatoes grown in beds with bare soil, black polyethylene, composted dairy manure, or hairy vetch. Early blight was reduced in plots with vetch compared with bare soil or compost in all years and compared with polyethylene cover in 1 year. Early blight was reduced in plots with polyethylene versus compost and bare soil in 1 and 2 years, respectively. Septoria leaf spot was reduced in plots with vetch versus other bed strategies in 1998 and bare soil or compost in 1999. This disease was reduced in plots with polyethylene versus bare soil or compost in 1998 and 1999. Soil coverage of tomato leaflets and soil particle dispersal were reduced in plots with polyethylene or vetch versus bare soil or compost in both years that these variables were assessed. Sensor wetness duration was reduced in plots with polyethylene or vetch versus bare soil or compost in one of two years. These findings suggest that foliar disease reduction in mulch was associated with reduced splash dispersal and, in one year, reduced leaf wetness.

The effect of a disposable probe cover on pulse oximetry.

The re-use of pulse oximeter probes presents the possibility of between-patient contamination. Use of a disposable polyethylene cover may reduce this risk. In a controlled, prospective study we examined the effect of such a cover on the accuracy of pulse oximetry. Each of ten volunteer subjects was monitored simultaneously by two identical Nellcor pulse oximeters, one with a plastic cover and the other, without a cover, used as a control. The pulse oximetry (SpO2) reading for each probe was recorded while subjects breathed 21% O2 and again while they breathed 10% O2. The probe cover was then swapped onto the other probe and the recordings were repeated. Ninety-five per cent limits of agreement in SpO2 (mean difference in SpO2 (1.95 x standard deviation of difference) between covered and non-covered probes were -0.6% to 0.6% while breathing 21% oxygen and -2.0% to 2.9% while breathing 10% oxygen. We conclude that a protective plastic sheath may induce a small error in pulse oximetry reading that is most marked during hypoxaemia. This error is unlikely to be of clinical significance.

THE RESPONSE OF SHOOT ACCUMULATION OF TRACE ELEMENTS IN CHINESE CABBAGE TO MICROCLIMATE MODIFICATION

In three consecutive years of field experiments (1994–96), three different environmental conditions for the growth of Chinese cabbage (Brassica pekinensis (Lour) Rupr. cv. Nagaoka 50) were established by using two cover treatments (T 1 and T 2) and a control uncovered cultivation (T 0). The T 1 [50 μm polyethylene cover; 20°C air temperature; 61.9% relative moisture; 207 W m−2 irradiance] and T 2 [a 17 gm−2 non-woven fleece; 18°C; 63.4%; 205 Wm−2] gave rise to differences in environmental conditions with respect to T 0 [14°C; 57.5%; 237 Wm−2]. We analysed chloride (Cl), barium (Ba), rubidium (Rb) and tin (Sn) in the whole tops of experimental plants. Chloride removal was high for Brassica pekinensis but considerably lower for Rb, giving intermediate values for Ba and Sn. The influence of environmental factors under T 1 increased trace-element removal and enhanced the usefulness for phytoremedation.

Emissions of NO , TVOC, CO 2, and aerosols from a pilot-scale wastewater treatment plant with intermittent aeration

Atmospheric emissions from a pilot wastewater treatment plant performing aerobic and anoxic processes were investigated. The experiment was performed by sealing the whole aeration tank with an airtight cover of polyethylene in order to obtain a defined flow rate of the off-gas. By measuring concentrations in the known flux of the off-gas emission rates were determined. Due to the dimensions of the pilot plant and the air and water flows these emission rates represent upper limits. The emission rates were put into relation to CO 2 to obtain normalized data that can be used for emission inventories. Normalized emission rates (g component×g −1 CO 2) were 8.9×10 −3 for TVOC, 6.6×10 −6 for non-methane hydrocarbons C 2–C 7 (NMHC), 2.1×10 −5 for NO and 3.0×10 −6 for particulate organic carbon (POC). Emission rates per capita equivalent per year accounted at the most for 244 g C TVOC, 0.18 g C NMHC, 0.58 g NO and 0.08 g C POC on a basis of 27,400 g CO 2 per capita. The non-aeration periods also contributed to the production of NO and TVOC emissions of approximately one-third of the total emissions. From this, we conclude that the implementation of denitrification stages in European wastewater treatment plants according to the EU-directive 91/271/EEC will increase trace gas emissions in Europe. However, according to our estimates, emissions of trace gases and aerosols from wastewater treatment compared to anthropogenic sources will still remain very low.

Balanço de radiação e fluxo de calor no solo em ambiente natural e protegido cultivado com pepineiro

São descritos os níveis de saldo de radiação, radiação global e fluxo de calor do/para o solo dentro e fora de estufas com cobertura de polietileno na época de outono-inverno e na de primavera-verão. Ao longo dos ciclos do experimento, os ambientes foram cultivados com pepineiro, cultivar Aoday, variedade Hokuroo, de crescimento indeterminado. Com base nos resultados, conclui-se que em estufa coberta com polietileno, a intensidade de incidência de energia solar por unidade de área diminui durante o período diurno, assim como as perdas por emissão, durante o período noturno. A transmissividade do polietileno foi alterada em função da época do ano e do tempo de exposição do material, passando de 70,8%, no inverno, para 74,9%, no verão. O fluxo de calor do/para o solo no ciclo de primavera-verão foi dependente do índice de área foliar da cultura.

Methyl bromide alternatives in tobacco, tomato and pepper transplant production

Metam-sodium, chloropicrin, 1,3-dichloropropene (1,3-D), 1,3-dichloropropene plus 17% chloropicrin (1,3-D+C-17) and 1,3-dichloropropene plus 35% chloropicrin (1,3-D+C-35) were evaluated alone and together under a polyethylene cover as alternatives for methyl bromide in tobacco, tomato and pepper transplant production over a two-year period. Eleven different weed species, 10 genera or species of fungi, two arthropods and four species of nematodes were evaluated in three different sites. All of the fumigant candidates were successful in controlling some of the pests. However, metam-sodium alone and in combination with 1,3-D+C-17, chloropicrin, and 1,3-D+C-35 were the most efficacious. Seventy-nine different parameters were measured over the two-year period including plant stands, vigour, plant heights and control of weeds, fungi, arthropods and nematodes. Metam-sodium and methyl bromide plus 2% chloropicrin (MeBrC) were not significantly different ( P=0.05) from each other in 76 of the 79 parameters evaluated; MeBrC was significantly better than metam-sodium for three of the 79 parameters. The combination of metam-sodium plus 1,3-D+C-17 was not significantly different from MeBrC for 74 of the 79 parameters tested. MeBrC was more efficacious than metam-sodium plus 1,3-D+C-17, for two of the 79 parameters, and metam-sodium plus 1,3-D+C-17 was significantly better than MeBrC for three of 79 parameters.

Albedo and estimates of net radiation for green beans under polyethylene cover and field conditions

This paper describes the albedo (r) and estimates of net radiation and global solar irradiance for green beans crop (Phaseolus vulgaris L.), cultivated in greenhouse with cover of polyethylene and field conditions, in Botucatu, SP, Brazil (22º 54' S; 48º 27' W; 850 m). The solar global irradiance (Rg) and solar reflected radiation (Rr) were used to estimate the albedo through the ratio between Rr and Rg. The diurnal curves of albedo were obtained for days with clear sky and partially cloudy conditions, for different phenological stages of the crop. The albedo ranged with the solar elevation, the environment and the phenological stages. The cloudiness range have almost no influence on the albedo diurnal amount. The estimation of radiation were made by linear regression, using the global solar irradiance (Rg) and net short-waves radiation (Rc) as independent variables. All estimates of radiation showed better adjustment for specific phenological periods compared to the entire crop growing cycle. The net radiation in the greenhouse has been estimated by the global solar irradiance measured at field conditions.

Radiation and energy balance of lettuce culture inside a polyethylene greenhouse

The objective of this paper was to describe the radiation and energy balance, during the lettuce (Lactuca sativa, L. cv. Verônica) crop cycle inside a polyethylene greenhouse. The radiation and energy balance was made inside a tunnel greenhouse with polyethylene cover (100 mum) and in an external area, both areas with 35 m². Global, reflected and net radiation, soil heat flux and air temperature (dry and humid) were measured during the crop cycle. A Datalogger, which operated at 1 Hz frequency, storing 5 minutes averages was utilized. The global (K<FONT FACE=Symbol>¯</FONT>) and reflected (K<FONT FACE=Symbol></FONT>) radiations showed that the average transmission of global radiation (K<FONT FACE=Symbol>¯</FONT>in / K<FONT FACE=Symbol>¯</FONT>ex) was almost constant, near to 79.59%, while the average ratio of reflected radiation (K<FONT FACE=Symbol></FONT>in / K<FONT FACE=Symbol></FONT>ex) was 69.21% with 8.47% standard-deviation. The normalized curves of short-wave net radiation, in relation to the global radiation (K*/ K<FONT FACE=Symbol>¯</FONT>), found for both environments, were almost constant at the beginning of cycle; this relation decreased in the final stage of culture. The normalized relation (Rn/ K<FONT FACE=Symbol>¯</FONT>) was bigger in the external area, about 12%, when the green culture covered the soil surface. The long-wave radiation balance average (L*) was bigger outside, about 50%. The energy balance, estimated in terms of vertical fluxes, showed that, for the external area, in average, 83.07% of total net radiation was converted in latent heat evaporation (LE), and 18% in soil heat flux (G), and 9.96% in sensible heat (H), while inside of the greenhouse, 58.71% of total net radiation was converted in LE, 42.68% in H, and 28.79% in G.

Resposta do tomateiro à fertirrigação potássica e cobertura plástica do solo

O objetivo do presente estudo foi determinar os efeitos da fertirrigação potássica e da cobertura do solo em película de plástico preto, na cultura do tomate. O experimento foi realizado na Universidade Federal de Viçosa, em solo Podzólico Vermelho-Amarelo câmbico. Os tratamentos, em cinco repetições, no delineamento em blocos casualizados, corresponderam a: (A) aplicação manual de 40% da dose recomendada de K no sulco de transplante e 60% aplicados manualmente, em cobertura; (B) aplicação manual de 40% da dose de K no sulco de transplante, e 60% aplicados por fertirrigação; (C) procedimento idêntico ao anterior, porém com o solo coberto por plástico preto; (D) aplicação de 100% da dose de K por fertirrigação e (E) procedimento idêntico ao anterior, porém com o solo coberto por plástico preto. Os tratamentos B, C, D e E foram irrigados por gotejamento. Maiores produções de tomates foram obtidas com a aplicação do K por fertirrigação do que com a aplicação manual. Estas produções, entretanto, não foram influenciadas pela aplicação total ou parcial de K por fertirrigação, nem pela presença de cobertura plástica do solo. Os teores de N-NO3-, N-orgânico, K, Ca e Mg no pecíolo do tomateiro não foram influenciados pelos tratamentos.

Cyperus rotundus Control by Solarization

ABSTRACT Soil solarization by means of polyethylene cover sheets was tested for the control of Cyperus rotundus weed infestation. Following solarization, which lasted for a period of approximately three months, the field was cultivated with carrots and dwarf green beans. Solarization was shown to provide a highly significant reduction of the weed population and to increase carrot yield. As for green beans, soil treatment was less effective and yield was not affected. In the solarized plots no weeding was needed during the vegetable crops cycle whereas the untreated plots required hand weeding within the first month from sowing. Soil solarization significantly reduced ant and earthworm numbers but had no effect on millipede population. Soil microbial biomass carbon (SMBC) was affected by solarization. However, actinomycete and bacterial populations, including nitrogen- fixing bacteria, showed no obvious pattern related to soil solarization.

Evaluation of the consolidation progress of a slurry by the SASW method

For several years a vacuum consolidation was applied on a disposal of dredged sludge in order to speed up the consolidation. The disposal with an initial thickness of about 8 m was covered with a sand layer of 0·5 m and topped with an high-density polyethylene (HDPE) cover. Since initially it was not allowed to cut open the HDPE for environmental reasons, it was decided to use the nondestructive spectral analysis of surface waves (SASW) method to evaluate of the degree and homogeneity of the consolidation. After a short description of the SASW field procedure and data processing, this paper presents the results of the evaluation of the stiffness of the sludge by the SASW method, which were later compared with laboratory test results. This SASW campaign showed that the consolidation was quite homogeneous in the disposal, although still a very low stiffness was measured. The SASW method was fast, cost-effective and well suited to the in situ evaluation of the vacuum consolidation technique.

Heavy metal‐induced accumulation of free proline in a metal‐tolerant and a nontolerant ecotype of Silene vulgaris

Accumulation of free proline in response to Cu, Cd and Zn was studied in nontolerant and metal‐tolerant Silene vulgaris (Moench) Garcke. In the nontolerant ecotype these metals induced a massive accumulation of proline, especially in the leaves. When compared at equimolar concentrations in the nutrient solution, Cu was the most effective inducer, followed by Cd and Zn, respectively. However, when compared at equal toxic strength, as estimated from the degree of root growth inhibition, proline accumulation decreased in the order Cd > Zn > Cu. The threshold exposure levels for proline accumulation coincided with the highest no‐effect‐concentrations for root growth. In the metal‐tolerant ecotype the constitutive proline concentration in the leaves was 5 to 6 times higher than in the nontolerant ecotype. Exposure to Cu and Zn, however, was without any effect on the leaf proline concentration, even at exposure levels that caused a 50% root growth inhibition. Only Cd, when present at concentrations above the highest no‐effect‐concentration for root growth, induced a further increase of the leaf proline content. Reducing transpiration by placing the plants under a transparent polyethylene cover almost completely inhibited proline accumulation, even at metal accumulation rates in the leaves that caused a 10‐fold increase of the proline level in leaves of uncovered plants. The results demonstrate that metal‐induced proline accumulation depends on the development of a metal‐induced water deficit in the leaves. Differential metal‐induced proline accumulation in distinctly metal‐tolerant ecotypes is a consequence, rather than a cause of differential metal tolerance.

Radiative cooling during the day: simulations and experiments on pigmented polyethylene cover foils

Pigmented foils can promote radiative cooling of an underlying object if they reflect most of the solar light and transmit a part of the thermal radiation in the atmospheric window in the infrared. In this paper we describe the optimization of optical properties, and simulations of thermal performance during the day for pigmented polyethylene foils. The tested pigment materials were ZnS, ZnSe, TiO 2, ZrO 2 and ZnO. It was found that only ZnS could promote cooling of a black body radiator in an insulated box at noon with the sun in zenith position. A 400 μm thick ZnS pigmented foil with a pigment volume fraction of 0.15 and a solar reflectance of 0.849 was tested in Tanzania. At noon the temperature was slightly above the ambient, and the heating power was approximately 7.2 Wm −2. However, this foil proved that cooling of a black surface could be obtained more than 19 hours per day in an arid location close to the equator.

Transmissividade a radiação solar do polietileno de baixa densidade utilizado em estufas

Determinou-se a transmissividade à radiação solar do polietileno de baixa densidade utilizado em estufas. O experimento foi conduzido em uma estufa tipo Capela com dimensões de 10m x 25m, coberta com polietileno transparente de baixa densidade, com espessura de 100µm e aditivado com anti-UV, instalada no Departamento de Fitotecnia da Universidade Federal de Santa Maria, RS - Brasil. A radiação solar global diária incidente no interior e exterior da estufa foi medida no período de julho de 1991 a janeiro de 1992 e também a fração difusa da radiação solar em dias com diferentes condições atmosféricas e de condensação no filme plástico durante o período de maio a julho de 1993. A transmissividade média da radiação solar global foi de 56,2% nas primeiras horas do dia e de 81,3% nas horas próximas ao meio-dia. A fração difusa da radiação solar global foi mais elevada no interior da estufa do que no exterior, evidenciando o efeito dispersante do plástico e da condensação do vapor d'água na superfície interna do filme.

Evaluation of an HDPE Geomembrane Landfill Cover Performance

The objective of this study is to develop a rational methodology for establishing the long-term behavior of a high density polyethylene geomembrane cover system. The procedures followed in this evaluation incorporated various concepts provided by other researchers and the examination of various sets of field data regarding the landfill settlement. The study includes the prediction of the long-term landfill cover settlement, examination of the change in lateral drainage and leakage rates as well as an examination of the change in high density polyethylene cover tensile tension due to the landfill cover settlement. The results of this study indicate the integrity of the high density polyethylene geomembrane regardless of the observed localized settlement in the landfill cover due to the solid waste decomposition and consolidation.

Effects of polyethylene film cover on the maturation and quality of ‘Fuyu’ persimmon fruit in New Zealand

Abstract Partially covering a block of ‘Fuyu’ persimmon trees with polyethylene (plastic) cover increased fruit colour, weight, soluble solids concentration, and lowered soluble tannins in each of two seasons. These improvements to fruit quality may have been the result of higher temperatures in the block partially covered with plastic. Plastic covering also increased spring shoot growth and advanced flowering by 7 days. The beginning of harvest was advanced by 1 week, and the spread of harvest reduced by 10 days. The effects of plastic covering on fruit quality varied between seasons. The increases in fruit colour and soluble solids concentration were greater in 1989 than in 1990. The increase in fruit weight and the decrease in soluble tannin content were greater in 1990 than in 1989.

Efecto de la intensidad de la luz sobre la floración y crecimiento del culantro, Eryngium foetidum L.

En la finca experimental Alzamora del Recinto Universitario de Mayagüez se evaluó cómo la intensidad de la luz afecta la floración y el crecimiento del culantro. El estudio se dividió en dos fases: la plantilla, que comprendió desde la siembra hasta la primera cosecha, y el retoño, desde la primera hasta la segunda cosecha. Las plantas se colocaron en cuatro estructuras cubiertas con plástico transparente. Tres de las estructuras también se cubrieron con Saran para reducir la intensidad de luz a 47, 63 y 73%. Se utiiizó un diseño de bloques completos al azar con tres repeticiones. Se observó un retraso significativo en la fecha de floración en plantas cultivadas a 63 y 7 3% de sombra comparado con las que crecieron a plena luz solar. Las plantas bajo sombra produjeron menos espigas y tuvieron un peso fresco más bajo que las que crecieron a plena luz solar. No hubo diferencia significativa en el número de hojas entre las distintas intensidades de luz. La disminución en la intensidad de luz aumentó significativamente el contenido de clorofila en las plantas.

Modeling Row Cover Effects on Microclimate and Yield: I. Growth Response of Tomato and Cucumber

Abstract Several polyethylene and fabric row cover materials, and clear and black polyethylene mulch, were evaluated in a 2-year field study. For cucumbers [Cucumis sativus (L.)], visible wilting and slowed growth rates of young transplants exposed to cold nights were minimized when grown under row covers that maintained high humidities and higher air and soil temperatures than in the exposed controls. Early cucumber yields were increased 2- to 6-fold by the use of covers. In contrast, tomatoes [Lycopersicon esculentum (Mill.)] showed no significant early yield increases, but a 63% reduction in early yield in 1985 under a perforated clear polyethylene cover. The frequency and duration of daytime air temperatures exceeding 35C had a negative impact on tomato fruit size, quality, and percentage marketable. For cucumber, the relationship between cumulative degree days (during the covered interval) and biomass, early, and total yields was linear (r2 between 0.70 and 0.82) with positive slope. Tomato yields could not be accurately predicted using this approach, but correlations were improved (for the 1985 data set) by using modified degree-day formulas incorporating a negative high-temperature factor.