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Comparison of Three Sprinkler Designs for Cold Protection in Shadehouses




Water isan economical source of heat to prevent cold damage tocertain crops; however, ways to reduce the quantity of this limited resource required for cold protection need to be developed. Rapidly rotating (6 rpm) wedge-drive impact sprinklers (conventional practice) were compared with a rotary action spray head and patented slow-rotating stream sprinklers for cold-protecting a subtropical crop {leather leaf fern [Rumohra adiantiformis (Forst.) Ching]} growing in shade houses. Treatments were applied in a3x3latin square design to nine 29x 29-m post-and-cable shade houses covered with woven polypropylene shade fabric designed to provide 73% shade. Temperatures in each shadehouse were monitored 45cm above the soil surface using four constantan-copper thermocouples. Ambient temperatures and wind speeds were monitored using additional thermocouples and an anemometer at a near by weather station. All sprinklers had 2.8mm orifices, were operated at0.25 Pa, and applied 0.5 (rotating stream, rotary) or 0.54 (wedge-drive) cm-hr1 o fwater. During an advective freeze with wind speeds up to 19m«s_1 and temperatures to-2°C, there were no temperature differences due to treatments. During aradiational freeze with readings below -2°Cfor over 12hr and a low of-5°C,all three irrigation systems maintained thermocouples at about -1°C. No significant damage to mature fronds were detected. Percentage of immature fronds damaged was not affected by treatments and ranged from 11% for rotary to 43% for the wedge-drive sprinkler treatments. The two newer sprinkler designs (rotary action spray head and patented slow-rotating stream) provided satisfactory protection equivalent to the industry standard (wedge-drive) while using about 10%less water.

Source: • HortScience Program Abstract Volume 32,#3

Keywords: Water source of heat advective freeze constantan-copper thermocouple Radiational freeze

Libraries: Floriculture

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