When low-energy consumption measures, such as natural ventilation and external sunshade, fail to reduce the indoor temperature in greenhouses, fan-pad evaporative cooling systems can be adopted ( Chai et al., 2008 ; Chen et al., 2012 ; Franco et
. These strategies include evaporative cooling of fruit through cycling water applications on and off, convective cooling of the air around the fruit, and hydrocooling the fruit continuously during the day. These strategies increase water use and may not
system was run from a photovoltaic array of fourteen 330-W panels (CS6U-330P; Canadian Solar Inc., Guelph, Ontario, Canada) whose power was inverted to AC using a 5-kW inverter (MPP 5048; MPP Solar Inc., Taipei, Taiwan). The evaporative cooling was
Abstract
The effect of evaporative cooling on budbreak and yield of Vitis vinifera L. (‘Perlette’ and ‘Thompson Seedless’) vines grown in the southern Jordan Valley in Israel was investigated. Overhead microsprinklers were operated from 0600 to 1800 hr daily during the autumn and winter months, either alone or in combination with cyanamide sprays after pruning. Evaporative cooling decreased the temperature of buds exposed to direct sunlight from 30° to 16°C and that of shaded buds from 25° to 13°. Evaporative cooling induced an early uniform budbreak. However, when evaporative cooling was combined with cyanamide spray, its effect was evident only during the initial phase of bud emergence. In 1985 cyanamide spray and evaporative cooling alone increased yield of ‘Perlette’ by 6% and 6% to 24%, respectively, and by 17% to 46% when both treatments were combined. In 1986 prolonged evaporative cooling increased the yield of ‘Perlette’ by 25% but, in combination with cyanamide, by only 11.6% over the unwetted cyanamide-treated control. In both years, evaporative cooling with or without cyanamide advanced fruit maturation.
An evaporative cooling system for apple trees was implemented. The system is automated to conserve irrigation water. The automation is based on the digital, integrated thermometer and thermostat chip embedded in the artificial fruit. The thermometer–thermostat chip drives a solid state relay. The relay controls a solenoid operated valve. A typical duty cycle consisted of 1 to 2 minutes of wetting (water on) to 4 to 10 minutes drying (water off). Differences in the length of duty cycles between individual chips were observed. The reliability of the system was adequate. The waterproofing of the system's electrical components was its weak point. Irrigation water deposits accumulated on the apple fruit surface during the growing season were readily removable with a simulated brush technique.
Abstract
Low vol overtree sprinkler irrigation was used on ‘Starkrimson Red Delicious’ apples during 2 successive growing seasons to determine the potential for moderating environmental extremes and reducing moisture stress through evaporative cooling. Irrigation, applied when air temp exceeded 87°F, substantially cooled plant tissues. In addition a residual cooling effect from evaporation of irrigation water following application was evident. The fruit exhibited the greatest amount of cooling (avg of 12.1° and 8.1°F in 1969 and 1970, respectively) because evaporation cooling negated radiation heating which normally caused fruit temp to be well above air temp. Cooling effects were proportional to length of operation of the irrigation system.
Abstract
Under the relatively dry and hot conditions which prevailed in 1972, both evaporative cooling and (2-chloroethyl)phosphonic acid (ethephon) improved fruit color and accelerated fruit maturity. The ethephon-evaporative cooling interaction on color and maturity was far superior to either one alone. Combined cooling-ethephon treatment resulted in 77% crop removal the first week of the season vs. only 5% in the control plot. Evaporative cooling also eliminated the leaf phytotoxicity of 2-(2,4,5-trichlorophenoxy)propionic acid (fenoprop), which was observed under heat stress conditions. In a drier production area, ethephon advanced maturity but did not increase red color. In an adjoining orchard ethephon applied after a 5 cm (2 inch) soil irrigation resulted in an additional 31% of the fruit surface showing red color within 10 days after application.
Abstract
Evaporative cooling, trickle, and no irrigation were compared under a reduced pesticide program and no pesticides for effects on pests of ‘Delicious’ apple (Malus domestica Borkh.) at 1 location in 1979 and at 2 locations in 1980. Evaporative cooling slightly increased foliar scab in one orchard and fruit scab at both locations on trees receiving no fungicides, but fungicides applied to one side of the trees overcame this effect. Irrigation treatments did not affect white rot incidence. Evaporative cooling lowered bitter rot incidence on non-sprayed trees in the year in which they were inoculated, apparently by washing off spores, but increased bitter rot on trees receiving fungicides in the following year when inoculum levels were much higher. Aphid colonies and damage from external fruit feeders and codling moth all increased under evaporative cooling when populations were high enough to detect differences between treatments, but this occurred during only one season at one location for each pest. Following either delayed dormant oil or selective miticide applications in June, evaporative cooling consistently maintained European red mites and usually maintained two-spotted spider mites below damaging levels, while pest mite populations on trickle- and non-irrigated trees resurged to high levels.
`Fuji' apples grown in the high light intensity of arid eastern Wash. are prone to sunscald damage. Evaporative cooling with over-tree sprinklers has become a commercially acceptable method for reducing the incidence of sunscald damage. A computer-controlled, over-tree evaporative cooling system was installed in a 3-yr-old commercial `Fuji'/M.9 orchard near Walla Walla, Wash. Over-tree sprinklers (Nelson R10 Mini Rotators) applied 280 or 560 1·min-1·ha-1 (30 or 60 GPM/A) when core temperatures were ≥33C (91.4F). Fruit skin and core temperatures were monitored with thermocouples. Fruit growth was not different between treatments. Skin color was improved by cooling, but the incidence of sunscald was low in all treatments. Commercial pack-out was measured and culls were evaluated. Fruit quality was analyzed at harvest and after 14 weeks storage. Titratable acids and soluble solids were higher in the 560 1·min-1·ha-1 treatment at harvest.
Abstract
Microsprinkler irrigation has proved effective in providing frost protection for young citrus trees, but there can be a risk of damaging trees during advective or windy freezes. The objectives of this study were to monitor evaporative cooling and to determine if height of young tree protection cold be increased to include the major scaffold branches. Microsprinklers were evaluated during a severely damaging advective freeze that occurred in central Florida in Jan. 1985. Trunk temperatures were measured at 15-, 30-, 45-, and 60-cm heights. By positioning the sprinkler at a 45° or higher angle, microsprinkler spray was aimed up into the young tree. This treatment was compared to the normal 15° low-angle spray pattern. Application rates on the wetted area were estimated to be 7 mm·hr−1 for high-angle treatment and 8.8 mm·hr−1 for low-angle treatment. With high-angle spray, trees were protected to a height of 85 cm, which was significantly higher than low-angle spray. Evaporative cooling below air temperature was not seen on irrigated trees. Continuous microsprinkler spray helped reduce evaporative cooling, but cooling did occur on a nearby tree that received only intermittent spray. Microsprinkler irrigation directed at an upward angle protected the trunk and scaffold branches of young trees in this particularly severe freeze and enhanced tree recovery.