The Photo-selective netting (Color-Nets) : an emerging approach

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The Photo-selective netting : an emerging approach towards… Crop Protection and Light-Quality Manipulation in One Technology By Mr.Pratik Rajendra ButtePatil. 1852/07 Final Year B.Tech Guide: Prof.N.N.Firke Dept: Farm Structures

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What actually photo-selective nets are ? Introduction…

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Plants can sense the quality, quantity and direction of light . The term Color-Nets is used here in a broad sense, to include nets that look colored to the human eye (e.g. Blue, Yellow, Red), they modify the non-visible spectrum and/or enhance light scattering e.g. Grey, White, Pearl i.e. “neutral-Color-Nets”. Netting that alters the spectral properties of light passing there through, may replace traditional nettings which merely reduce the quantity of light. Are based on the incorporation of various chromatic additives, light dispersive and reflective elements into the netting materials during manufacturing.

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Some Important Definitions & Concepts….

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Light-modifying net: 1) A net that can modify light quality (namely, spectral, scattering, relative content of indirect light, and/or thermal properties. Coloration (of fruit)- Intensity and/or uniformity of color distribution on the fruit surface. Phytochrome: 1) The red and far-red light sensor that has absorption peaks in red and far-red regions of the spectrum, respectively 2) Controls photo-morphogenesis. Phytochrome Photoequilibrium (f): Amount of phytochrome in the Pfr form relative to total phytochrome f depends largely on the absorption of red and far-red wavelengths by the plant and therefore, f decreases with decreasing R:FR ratio.

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Importance of shed-Net application over plants….

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Emergence Vegetative growth Plant size Branching Branch elongation Dwarfing Plant vigor Development of the root system Development of the canopy Bushiness Leaf size and variegation Fruit-set Fruit drop Sugar content of fruit Acid content of fruit Size of fruit Content of bioactive & aromatic compounds Sunburn Coloration Post-harvest life Timing and quality of flowering It is useful for influencing plant characteristics, such as….

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Where to implement them?

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Foliage crops/ Vegetables Photo-selective netting was tested in foliage crops, traditionally cultured under black shade nets of 50-80% shading . The Red and Yellow nets were found to specifically stimulate vegetative growth rate and vigour, the Blue net caused dwarfing Grey net specifically enhanced branching and bushiness, and also reduced leaf size and variegation . However, frequently excessive irradiation in the summer, causes sunburns as well as undesirable flowering, which reduces the quality of the edible parts, so shed-nets should be used. The method was found to improve both the yield and quality of the summer crops. Producing high-quality fruit, avoiding sunburns, and saving on irrigation.

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Cut flowers Were found to develop longer and thicker flowering stems under the Red and Yellow nets, while shorter under the Blue, compared with their equivalent black shade net. Additionally, the Red net induced shorter time to flowering in some species. The highly dispersive Pearl net was recently reported to enhance branching of some plants, while in others it increased the number of flowers per branch, compared with a black net of the same shading capacity.

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Fruit trees-Low-shading photo-selective netting of fruit tree crops (e.g. peach, apple, pear, table grapes) Reduce heat/chill/wind stresses, enhancing photosynthesis and canopy development, compared with the un-netted orchards. The photo-selective responses include fruit-set, harvest time (early or late maturation), and fruit yield, size, color,internal and external quality Strawberries It is observed that light-modifying netting of strawberries affects the harvest season, enabling to go on harvesting high quality fruit until early summer, in areas where the harvest season of non-netted strawberries end in early spring. The Red and Pearl increased the percentage of top quality fruit.

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Pomegranates Which net to be used? : Aluminet (30 % shade), White 22, Gray 30, Black 30. Sunburn was reduced by 90% under all nets. Aluminet 30 also resulted in better dispersion of the red color over the fruit surface. Aluminet 50 caused smaller fruit, delayed fruit maturation and less red coloration, indicating too much shade.

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How to implement Shed-Net ?

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The nets may be applied in any position that increases the indirect/direct light ratio, such as horizontal covering, zig-zag roofs, covering a greenhouse, or under a greenhouse roof. In particular, the inventors found that nets suspended , preferably 1.5 m or more above the plant canopy are especially efficient. However, when used in constructions closed from all sides, the nets may induce secondary effects on the plant microclimate, and these secondary effects may sometimes be undesirable.

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Lets see….. How does the netting itself affect the crop?

Light quality modification by Color-Nets. : 

Light quality modification by Color-Nets.

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Anti-drip effect Droplets formed at the inside surface of greenhouse films due to water-condensation , they reduce light-transmission by 15-30% and increase the incidence of certain diseases. “Anti-dripping" films eliminate droplets and form instead a continuous thin layer of water running down the sides. Benefits…. More light in the greenhouse Higher crop yield Earlier harvesting Better quality of crop, higher commercial value Fewer diseases Reduced need for pesticides

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Light diffusion Light from the sun passing through a greenhouse film and entering a greenhouse is split into direct and diffused. It is now generally accepted that diffused light has a positive effect on plant growth, especially for spring and summer crops and in areas with strong sunlight. Reduces shadows, ensures more uniform distribution of light in the greenhouse so that it reaches even the lower parts of the plants offers a moderate cooling effect. So avoiding “sun burns” or “scorching“ & promoting equal feeding to all the parts of the plant.

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Thermic effect Special thermic films, containing a combination Infra-Red additives which absorb the Infra-Red radiation and reduce heat losses during night & day. Benefits… Protection from frost and low temperature. Smoother temperature drop and higher night temperatures overall. Reduced energy consumption for heating & cooling. Higher crop yield. Earlier harvesting. Better quality of crops.

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Cooling effect There is growing requirement for films that cut-down excessive heat during day-time and maintain a cooler environment in the greenhouse. Reflect and/or absorb the Near Infra-Red (NIR) Radiation, the part of solar spectrum carrying most of the heat entering a greenhouse in day-time, thus reducing the heat inside the greenhouse during the day. special double-effect "silver" film (cooling during day, more thermic during night) "Selective interference" films

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Anti-mist effect To allow the use of anti-dripping films, with all their benefits, without fear of the mist (fog) that is sometimes formed during sun-set and dawn in greenhouses covered with such films

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Disease control effect A range of special disease control films, which contribute efficiently in IPM "Integrated Pest Management" They absorb UV-radiation up to 390 nm, thus achieving: Reduction of the population of whiteflies, miners, aphids and other insects in greenhouses, thereby also reducing the viral infections due to insects. Reduction of "blackening" of red rose petals, thereby increasing their commercial value.

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Results and discussions…

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Shading and scattering of the solar radiation by some of the nets in the Photosynthesis Active Region (PAR) and in the UV (A+B) are given….

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Note: Higher level of PAR light presumably lead to increased photosynthesis and the increased number of leaves with the red shade cloth

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As demonstrated in Table 1, shading ranged between 49.2 – 57.6% (April 7, 1998) and 50.8 – 59.0% (October 14, 1999) for a single net, and between 73.4 – 79.8% (April 29, 1998) for double nets. The slightly higher shading effect of the Green, Red, and Blue over the neutral nets might result from more dust held by the first three nets, due to their higher knitting density The Green, Red and Blue nets caused 74-79% shading in the 300-400 nm range.

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References…. Rajapakse, N.C. and Shahak, Y. 2007. Light quality manipulation by horticulture industry. In: G. Whitelam and K. Halliday (eds.), Light and Plant Development, Blackwell Publishing, UK, pp 290-312 2. Shahak, Y., Ganelevin R., Gussakovsky, E.E., Oren-Shamir, M., Gal E., Díaz, M., Callejón, Á.J., Camacho, F. and Fernández-Rodriguez E.J. 2004c. Effects of the modification of light quality by photo-selective shade nets (ChromatiNet) on the physiology, yield and quality of crops. Ben-Yakir, D., Hadar, M.D., Offir, Y. Chen, M. and Tregerman, M. 2008. Protecting crops from pests using Optinet® screens and Chromatinet® shading nets.

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Conclusion… So shed nets should be implemented for crops as per their requirements for….. Proper light diffusion and modifications. Best quality of fruits or flowers. High market value. Proper and Healthy growth.

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Thank you !