Shading Nets Research Articles

Growing ‘Hass’ avocado fruit under different coloured shade netting improves the marketable yield and affects fruit ripening

Abstract Sunburn damage due to excessive solar radiation is one of the major problems affecting the avocado fruit production. Shade netting has been introduced so that growers can cover their orchards with the nets to protect their trees/fruit. However, little is known on the effect of different coloured shade netting on avocado fruit quality. Thus, the influence of blue, red and white photo selective netting on marketable yield, physicochemical characteristics and incidence of anthracnose in ‘Hass’ avocado fruit was investigated. Blue and white netting improved the marketable yield, and accelerated fruit ripening after 28 d cold storage at 5.5 °C followed by 5 d at shelf-life conditions. Ripening, as indicated by fruit softening, correlated well with the content of d -mannoheptulose. The concentration of α–tocopherol, oleic acid and phenolic acids was also affected by growing conditions, due to different coloured shade netting being used. However, incidence of anthracnose was reduced on the 5th d at shelf-life conditions due to delayed ripening, higher phenylalanine ammonia lyase activity, and epicatechin content in the pericarp. White and blue netting appear to be a suitable pre-harvest tool to improve the marketable yield.

Light modification by color nets improve quality of lettuce from summer production

Abstract The effects of utilization of different color shade nets in lettuce production during the summer season were evaluated in Serbian climate conditions for pearl, blue, red and black shade nets in comparison to open field production. Applied shade nets (with shade index of 50%) significantly reduced solar irradiation (from 890 in open field to 400–560 Wm−2 under the shade nets) and photosynthetically active radiation (from 2020 in open field to less than 1000 μmol s−1 m−2 under the shade nets). Color shade nets affected both, properties of lettuce during the growing period and its morphological properties. Namely, the leaf area index was increased, lettuce heads were characterized with significantly higher marketable head weight and head diameter, the period from planting to bolting was significantly shorter, the outer leafs were characterized with more intensive green tone (–a*) and the lettuce leafs were softer and more tender for lettuce grown under the shade nets in comparison to open field production. In respect to lettuce composition, total chlorophyll content, contents of both chlorophyll a and chlorophyll b, as well as carotenoid content were significantly higher in shaded leaves of lettuce than in the control plants. Significantly higher (30.78 mg GAE g−1 d.m.) total phenol content was determined in plants grown under the pearl shade nets accompanied with significantly higher flavonoids content (14.28 mg RE g−1 d.m.) and significantly higher antioxidant properties (lower EC50 DPPH values) in comparison to all other nets. However, the antioxidant properties of control plants were at the same level as for the pearl net, in spite of lower phenols and flavonoids content.

Training of Growers and Extension Agents in the Dominican Republic on Managing Heat Stress of Bell Pepper (Capsicum annum L.) Grown in High Tunnels

The Dominican Republic is located in the Hispaniola Island in the Caribbean region. Its climate differs substantially over short distances and is the most diverse of the Caribbean. Annual average temperature is 25 °C, ranging from 18 °C (at higher elevations) to 28 °C (at sea level). Average annual rainfall is 1500 mm. Although sugar, coffee, cocoa, and tobacco are the principal cash crops of the country, peppers are increasing in popularity on the country’s exportation market. Bell peppers grown in high tunnels and greenhouses may be impacted by high temperatures that result in reduced fruit yield and quality. In this article, we make a short review of cooling techniques for high tunnels and share the experience of training bell pepper growers and extension personnel from the Dominican Republic regions of San José de Ocoa and Constanza on how to manage heat stress of bell peppers grown inside high tunnels. Bell pepper plants inside high tunnels showed symptoms of heat stress, including reduced plant and fruit size, small fruit number, and a mild leaf chlorosis. In both regions, but particularly in the warmer region, San José Ocoa, because of occurrences of high temperatures inside the high tunnels, growers were advised to use well-ventilated high tunnels, such as structures with plastic film on the top and screen net on the sides. Other strategies such as shade nets (30% to 40% shade) placed on top of the high tunnel or whitewash paint applied on the high tunnel cover may also help reduce air and soil temperatures inside the tunnel. Use of white or silver reflective mulch, instead of the commonly used black mulch, may provide additional reduction of soil temperature. In conclusion, high tunnel structures developed for temperate regions, with limited to poor ventilation, may result in excessively high temperatures inside the high tunnels and thus were not recommended for the Dominican Republic regions of this study. More research is necessary on adequate high tunnel design and cooling techniques for high tunnel production, particularly in tropical regions.

Impact of Shading Net Color on Phytochemical Contents in Two Chili Pepper Hybrids Cultivated Under Greenhouse Conditions

The objective of this study was to understand the combined effect of shading treatment and harvest time on pungency, ascorbic acid content, market-quality pepper yield, and photosynthetic activity in a yellow ‘Star Flame’ and ‘Fire Flame’ F1 hybrid pepper cultivar (Capsicum annuum). Plants were cultivated in a greenhouse under white, red, and green shading nets and compared to those grown under unshaded control conditions. The ascorbic acid and pungency parameters were analyzed by high-performance liquid chromatographic methods. Ascorbic acid, a compound of high nutritive value in pepper, was highest in fruits gathered during the first summer harvest in both hybrids. The ascorbic acid content was found to be further increased in fruits from plants grown under white net shading in both ‘Star Flame’ and ‘Fire Flame’. Total capsaicinoid contents in ‘Star Flame’ were influenced by the interaction of shading treatment and harvest time ( p = 0.004), with the lowest amounts (241.2-251.5 mg·kg-1 fresh weight) resulting from white and red shading treatments at the early autumn harvest. In ‘Fire Flame’, both shading treatment ( p = 0.009) and harvest time ( p < 0.001) affected total capsaicinoid contents. We observed significantly higher total capsaicinoid contents in control fruits compared to that resulting from red and green shading treatments at the second harvest, and that resulting from red shading treatment at the third harvest. Analysis of photosynthetic activity revealed a significant and negative correlation between Fv/Fm values and total capsaicinoid contents in both hybrids ( p < 0.001). Based on the obtained results, the harvest of peppers during summer should be promoted to produce fruits with high pungency.

Mathematical growth model for organically grown pepper transplants

This study was conducted in a temperature-controlled greenhouse, with six partitions, during different growing periods in the year (seeds sown on 29 September for 1st period; 2 December for 2nd period; 18 March for 3rd period and 6 July for 4th period). Immediately after sowing, shading material with 50% shading capacity was used in 1, 2 and 3 layers in each period to create different light intensities. A control treatment without shading nets was also created. Pepper (Capsicum annum L. cv Yalova Çarliston) was used as the plant material. Transplant height, stem diameter, leaf area, total dry weight, leaf stomatal conductivity and leaf chlorophyll contents were measured as quality parameters for the transplants. Significant differences were observed in the quality parameters related to the growing periods, shading treatments and growing period × shading interactions. A mathematical model was developed to estimate the number of days required to produce ready transplants, by using the variation values created in the different growing periods and shading treatments.

The use of shading nets for the greenhouse cultivation of sweet pepper in the Mediterranean area

The Mediterranean area is characterized by hot summers that, especially inside greenhouses, can determine non-optimal conditions for the growth of vegetable crops. In Southern Italy, the use of shading nets or the application of calcium hydroxide (whitening) on the cover material of the greenhouse is often used by farmers to improve micro-climatic conditions for crops and to obtain a healthier environment for workers. In recent years, thanks to their cheaper price accompanied by improved photo selective properties, plastic nets are often used for shading purposes, combining the shade effect with their specific features useful for the crop growth. Like other vegetable crops in the Mediterranean area, sweet pepper cultivation in greenhouses can benefit by shading during the late spring and summer months. With the aim of determining the effects of different greenhouse shading methods on the cultivation of sweet pepper, a trial was carried out in Battipaglia (Campania Region - Southern Italy), comparing cover whitening, made by slaked lime, with two plastic nets, a reflective aluminized cloth having 50% of shade level (Aluminet) and a photo-selective red net having 30% of shade level (red Chromatinet), resulting the colored shading nets most used by farmers in the study area. In addition, an unshaded greenhouse was utilized as a control. The plastic nets, as well as allowing a shading effect, contributed to avoid the decrease in the greenhouse temperature overnight (Aluminet), as well as to modify the spectrum of the transmitted light (Chromatinet). In order to investigate the influence of the studied nets on the growth of sweet pepper, yield quantitative and qualitative traits were performed. Furthermore, spectro-radiometrical and mechanical characterizations of nets, through laboratory tests, were carried-out. The results obtained by these tests, confirming the relationship between the porosity of a net and its transmittance in the solar range, allow to evaluate the different shading and transmittance effects.

Influence of colour net shading on quantity and quality of sweet pepper yield

Influence of colour net shading on quantity and quality of sweet pepper yield

Innovative techniques to reduce chilling injuries in mango (Mangifera Indica L.) trees under mediterranean climate

As a tropical tree, mango (Mangifera indica L.) cultivated in Mediterranean climate needs protection against low temperatures. The aim of this work is to study the effect of traditional individual protective canopy protection systems in comparison with innovative typologies designed for this experiment on the physiological response of young mango trees during the cold season. We selected 25 four-year-old mango trees cv ‘Glenn’. Trees were divided into five different groups: not covered trees (NC); trees with windbreak protection using a shading net (SN); trees with windbreak protection using non-woven sheets (WB); fully covered trees using non-woven sheets (FC); fully covered trees with non-woven sheets and the addition of a 'heat exchanger' device (FC+). Their canopies were fully covered (FC) and (FC+) or enclosed by a hand-made individual windbreaks (SN and WB). We studied the evolution of temperature inside the canopy and evaluated the threshold of damage on leaves and shoots. We also monitored soil temperature under the trees. Precision self-made data loggers were assembled. A exchanger was realized for this experiment to try to recover heat from the ground and place it under the canopy of the plants. It was made with a 50 cm U-shaped aluminum pipeline using recycled materials; this was placed horizontally, 50 cm deep in the soil with one of two extremities above the soil and the other within the canopy. NC trees were damaged by cold temperature. More particular, the young shoot was injured by necrosis followed by fungal disease. The same behavior was observed in SN and WB when the canopy was only enclosed by the protection whereas FC tree shoots were intact. Non-woven sheets preserved intact the shoots only in the FC trees, as the canopies were completely covered by a closed space because the leaves and shoots were isolated from the outside. The ‘heat exchanger’ device increased, however minimally, the temperature in the closed space containing the canopy. The use of non-woven sheets, covering completely the canopy, allowed to preserve the shoots for future tree development.

Response of Baby Spinach (Spinacia oleracea L.) to Photoselective Nettings on Growth and Postharvest Quality

Manipulation of microenvironments by means of photoselective nettings is widely used to improve the productivity and quality of high-value vegetables. The aim of this study was to investigate the effect of photoselective nettings on growth, productivity, and postharvest quality attributes of baby spinach. Baby spinach cv. Ohio was grown from seeds, and the trial was repeated. Plants were planted in an open field (control) and under closed nets, viz., black, pearl, yellow, and red nets. At harvest, baby spinach leaves were subjected to 4, 10, and 20 °C storage temperatures for 12 days. Crops grown under black nets and stored at 4 °C retained higher level of antioxidant activity (0.23 g·kg−1), whereas the least level of antioxidant activity was observed in baby spinach grown under red and yellow shade nets (0.01 g·kg−1). Similar trend was evident with flavonoid content where baby spinach leaves grown under black nets maintained high level of flavonoids at 4, 10, and 20 °C during storage period compared with other shade nets and the control. The study control showed a better potential in retaining antioxidant activity over red and yellow shade nets. Results showed that black shade nettings have the potential to reduce water loss, decay incidents, and maintain flavonoid content and antioxidant activity followed by pearl and yellow nets.

Growth, photosynthetic pigments and production of essential oil of long-pepper under different light conditions.

Piper hispidinervum C. DC. is popularly known as long-pepper and it owns a commercial value due to the essential oil it produces. Long-pepper oil is rich in safrole and eugenoln components that have insecticidal, fungicidal and bactericidal activity. It has been establish that to medicinal plants light influences not only growth but also essential oil production. The growth, the content of photosynthetic pigments and the essential oil production of Piper hispidinervum at greenhouses with different light conditions was evaluated. The treatments were characterized by cultivation of plants for 180 days under different light conditions, produced by shading greenhouses with 50% and 30% of natural incident irradiance, two colored shading nets red (RN) and blue (BN) both blocking 50% of the incident radiation and one treatment at full-sun (0% of shade). The results showed that the treatments of 50% shade and RN and BN were the ones which stimulated the greater growth. Blue and red light also had the best production of photosynthetic pigments. Essential oil yielded more under full sun therefore this is the most indicated condition to produce seedlings for the chemical and pharmaceutical industry.

Photosynthetic pigments content and chloroplast characteristics of tamarind leaves in response to different colored shading nets

Photosynthetic pigments content and chloroplast characteristics of tamarind leaves in response to different colored shading nets

Fruit cracking in litchi (Litchi chinensis): An overview

Litchi (Litchi chinensis Sonn.), an arillate fruit species of China origin, possessed a unique structure comprising thin and leathery pericarp that enclosed the aril as its edible part. Fruit cracking is a serious physiological disorder in litchi that occurs during its growth and development, and causes significant loss of economic yield. Fruit cracking in litchi coincides with a period characterized by high day temperature (35-40°C) and low relative humidity (60%). It entails the implicated roles of both internal and external factors. Besides climatic effects, abnormal development of the skin during early fruit growth promotes the disorder. In this context, a concept, ball skin versus bladder effect was theorized to describe the relationship between a pre-grown skin and a growing aril. To further conceptualize the problem, Zig-zag Unfolding model was developed which decipher the role of spongy tissue in pericarp extensibility necessary for preventing pericarp cracking. Cracking occurs during the final stage of fruit growth when the aril develops and exerts pressure on the inactively growing pericarp. Thus, a balance between turgor pressure from the expanding aril and the mechanical structure and elasticity of skin is indispensable to prevent fruit cracking. Fruit cracking can be controlled by application of calcium nitrate (0.5 - 1%), borax (0.4 - 0.8%), Zn (0.4%), GA3 (10 ppm) alone or in combinations assured with timely irrigation, mulching, bagging of fruit bunches, use of shade nets and growing cracking resistant cultivars.

Changes in concentration of volatile compounds in response to defoliation of Muscat of Alexandria grapevines grown under a traditional farming system

Linalool is a monoterpene, which exhibits floral and spicy aromas as well as a variety of pharmacological effects, including antioxidant, anti-inflammatory, and cardiovascular. Wine flavor is highly dependent on the chemical compounds of berries. The objective of this study was to evaluate the concentration of volatile compounds, especially linalool, in grapes (Vitis vinifera L.) ‘Muscat of Alexandria’ grown under different cluster light exposure. Four defoliation treatments were applied at veraison, and changed the light environment at the fruit zone. Severe defoliation (T1): leaves were manually removed from the 1st to the 8th node of each shoot, partial defoliation (T2): leaves were manually removed from the 1st to the 4th, semi-shaded clusters (T3): un-trimmed vines were covered with an 80% shade netting; and (T4) control treatment with non-intervention during season 2014-2015. Free terpenes were extracted using headspace solid-phase microextraction (HS-SPME), and the concentration of volatile compounds was determined using gas chromatography coupled to a flame ionization detector (GC-FID). The study was conducted in two different locations of the Itata Valley in Chile. Linalool concentration was more prevalent in treatments with higher cluster exposure. The treatment with the highest defoliation showed a linalool concentration 40% higher than the control treatment. Higher levels of defoliation in grapevines grown under a traditional farming system result in an increased concentration of volatiles compounds, particularly monoterpenes, where Cerro Verde and Pinihue reached linalool concentrations of 19.1 and 21.7 (g L-1, respectively. These results revealed important differences in the behavior of the synthesis of linalool.

Growth characteristics and ginsenoside contents of Korean ginseng (Panax ginseng C.A. Meyer) by shade materials and green manure crops

ABSTRACT This research carried out to figure out the effect of the green manure crop cultivated at a preparation field and the shading net on the growth, development, and quality of ginseng. Followings are results obtained from the research. Leaf width of ginseng under the shading net of a two-layered blue and two-layered black polythylene net (TBTBPN) was good at rye and hairy vetch cultured group. Leaf length of ginseng under the shading net of a three- layered blue and one-layered black polyethylene net (TBOBPN) was good at barley and hairy vetch cultured group. Meanwhile, leaf width was good at hairy vetch cultured group. Leaf length of ginseng under a blue polyethylene sheet (BPS) was good at a barley and barley + hairy vetch cultured group, but stem length was shorter compare to other shading net cultivations. Root weight of ginseng was good under the shading net of a two-layered blue and two-layered black polyethylene net (TBTBPN) at a rye and hairy vetch cultured group, and was good under the shading net of a three-layered blue and one- layered black polyethylene net (TBOBPN) at a barley + hairy vetch cultured group, but there was no significant difference under blackout screen according to manure crop varieties. Ratio of rusty root was 10.2% at the barley cultured group under the shading net of a two-layered blue and two-layered black polyethylene net (TBTBPN), and was 23.1% at hairy vetch cultured group under shading net of a three-layered blue and one-layered black polyethylene net (TBOBPN). Ratio of rusty root was the lowest at a rye cultured group regardless the shading nets. Content of the ginsenoside was the highest at the rye cultured group under the shading net of two-layered blue and two-layered black polyethylene net (TBTBPN), was the highest at the barley cultured group under the shading net of a three-layered blue and one-layered black polyethylene net (TBOBPN), and was the highest at the rye cultured group under the blackout screen.Keywords : ginseng, green manure crop, shade net, ginsenoside

Initial growth of Costus longebracteolatus and Costus spiralis ‘French Kiss’ under different light conditions

The Brazilian native Costus longebracteolatus and Costus spiralis ‘French Kiss’, in the family Costaceae, have been used as both cut flowers and cut foliage. It is known that Costus species grow better under partial shade, but studies on the influence of shading or light on plant growth, development, and flower production are still incipient. As this kind of information is essential on planning of planting, production, and agribusiness activities, the objective of this research was to evaluate the influence of different colored shade nets and light conditions on the initial growth of both C. longebracteolatus and C. spiralis ‘French Kiss’. Plants, obtained from cuttings of pseudostems, were cultivated under six light conditions, which comprised six treatments, along 270 days: red net with 50% shading, blue net with 50% shading, black net with 70% shading, black net with 50% shading, black net with 30% shading, and full sun. The initial growth of C. longebracteolatus (up to 270 days) is more successful under the blue net with 50% shading, which promoted highest values of pseudostem length and dry matter of aerial part. For C. spiralis ‘French Kiss’ plants, both the red and blue nets with 50% shading implied best results and differed for the other treatments with greater pseudostem length. Plant exposure to full sun inhibited growth and development, and favored early leaf necrosis.

Varying percentages of full uniform shading of a PV module in a controlled environment yields linear power reduction

Partial shading of a PV module has received much attention over the past few years, as it results in uneven cell power generation, compromising a PV system performance. Full uniform shading of a PV module has not received as much attention. This article correlates the percentage of full uniform shading of a given PV module within a controlled environment to its output power. The percentage of full uniform shading provided by shade nets was firstly determined. These shade nets are then used to cover a specific PV module (experimental system), while an identical PV module remains totally unshaded (control system). Increasing percentages of full uniform shading negatively affected the direct beam component in a linear way. Decreasing the light intensity falling on the PV model exhibited a linear increase in the percentage of output power reduction of the PV module. This is observed in that a shade net providing 36% of full uniform shading resulted in a 56% output power reduction, while a 63% full uniform shading net yielded 82% power reduction. These results hold a strong promise to improve current simulation modules that focus on determining the output power of a given PV array under specific environmental conditions or for specialised geographical locations.

Physiological and behavioral responses of Nellore steers to artificial shading in an intensive production system

The influence of artificial shading on environmental variables and on behavioral responses of Nellore steers in an intensive production system was evaluated in this study. The experiment was conducted in the experimental feedlot of the Department of Animal Science at Universidade Estadual de Goiás, from July to October 2014. Forty-eight male Nellore cattle with an average initial weight of 310 kg were kept in double 24-m2 stalls, in a total of 24 stalls. Of these, six were in the open air; six were covered with black shade netting of 30% light interception; six with black shade netting 50%; and six with black shade netting 80%, providing 6 m2 of shade per stall. Temperature-humidity index (THI) and respiratory frequency (RF) were assessed twice weekly and behavior was evaluated fortnightly during 12 h, between 06:00 h and 18.00 h. Feeding behavior, rumination, rest, and social activities such as body care and playful and abnormal activities were observed. A significant increase was found in THI and RF as the shading levels decreased, while a significant difference was recorded in rest and in other activities, water intake, and play behavior. Rest time and playful behavior increased significantly, and other activities and water intake decreased with the increase in shading levels. Shading does not change the time spent on feeding behaviors and rumination, or the frequencies of urination, defecation, cleaning other animals, self-cleaning, and social and abnormal types of behavior. The use of black shade netting of 80% light interception provides greater comfort to animals, promoting welfare and quality of life to them.

Performance of Nellore males under different artificial shading levels in the feedlot

The objective of this study was to evaluate the influence of artificial shading on weight gain and meat quality of male Nellore cattle in an intensive production system. The experiment was conducted in the experimental feedlot of the Course of Animal Science at Universidade Estadual de Goiás, from July to October 2014. Forty-eight male Nellore cattle with an average initial weight of 310 kg were kept in double 24-m2 stalls, in a total of 24 stalls. Of these, six were in the open air; six were covered with black shade netting of 30% light interception; six with black shade netting 50%; and six with black shade netting 80%, providing 6 m2 of shade per stall. The ration supplied to the animals and the orts left in the trough were weighed daily to determine intake, and the temperature-humidity index (THI) was measured twice weekly. Animals were weighed for the first time at the start of the experiment, and then another three times until the end, which was followed by the slaughter and assessments of performance and meat quality. A difference (p &amp;lt; 0.05) was observed between the average THI values, with the highest value found in the stalls without artificial shading. No difference (p &amp;gt; 0.05) was observed for feed intake, initial weight, final weight, total weight gain, average daily weight gain, carcass yield, marbling, texture, fatness, backfat thickness, loin-eye area, color, thigh length and circumference, leg length and circumference, or carcass length between the animals on the different treatments. The use of artificial shading does not have a significant effect on performance or meat quality of feedlot Nellore cattle when the ambient temperature is within the thermal comfort zone.

Effects of shading nets on sunburn and quality of ‘Granny Smith’ apple fruits

Sunburn causes some damage to apple orchards and it results from heat stress to the fruit leading to injury of the affected cells. A net shield is a good option for protection of apple trees against damage by hail, strong wind, and birds. Also, it reduces sunburn and russeting of fruits, provides better color and skin uniformity. This study was carried out to determine the effects of two different light transmission shade nets (black and white) on 'Granny Smith' apple fruits sunburn and quality. The experiment was conducted in commercial apple orchard in Denizli, west part of Turkey during two consecutive years (2012-2013). Fruit sunburn ratio was 24% under open sky (without net) condition. Black or white shading nets reduced sunburn of fruits without negative effects on fruit quality and maturation.

Effect of different coloured shade nets on production and quality of cordyline

Cordyline terminalis is an important ornamental plant used for its beautiful foliage as cut green. This plant prefers shade for optimum growth. The effect of different coloured shade nets (red, green, black, and white with 50% shading intensity) along with control (without shade net) on production and quality of Cordyline terminalis was studied. The effect of spectral control of light on physiology and vegetative development was evaluated at different crop growth stages. The results showed that plants grown under shade nets produce good quality foliage and biomass irrespective of colour. The cut greens grown under red and white shade nets were exposed to higher PAR and transmittance than other colour nets and hence had better performance in terms of plant height, number of leaves, biomass, leaf area, photosynthetic rate, harvest index compared to control. Vase life of the foliage was higher under coloured shade nets when compared to open condition but significance difference was not found between different colours. White and red shade nets were found to be best for growing cordyline.