Elevated Microsprinklers Improve Protection of Citrus Trees in an Advective Freeze

Abstract

<jats:p>The severe advective freeze of 23-26 Dec. 1989 killed most nonprotected trees in Florida's northern citrus region. Minimum temperatures reached - 8.3C with &gt;43 hours below freezing. Microsprinklers elevated to a height of 0.6 or 0.9 m and placed inside the canopy of young `Hamlin' and navel orange trees <jats:italic>[Citrus sinensis</jats:italic> (L.) Osb.] provided excellent protection to heights well above 1 m. Initial survival height of trees with emitters elevated to 0.9 m was higher than has been reported for microsprinklers at a conventional 0.2-m height in earlier severe freezes. Trees rapidly approached prefreeze canopy size from regrowth of the protected scaffold branches. Six months after the freeze, trees protected by microsprinklers elevated to 0.6 m and delivering 26 or 47 liters·hour<jats:sup>-1</jats:sup> had regrown to a height of 1.4 or 1.7 m, respectively. Trees with microsprinklers at a height of 0.9 m and delivering 101 liters·hour <jats:sup>-1</jats:sup> had regrown to a height of 2.5 m. Trees with no microsprinkler irrigation were killed to the ground. Twelve months after the freeze, trees with elevated microsprinklers were still significantly taller and showed greater recovery than those with microsprinklers near the ground.</jats:p>

Freeze Risk and Protection Measures of Satsuma Mandarins Grown in the Southeastern United States

“…Microsprinkler irrigation uses sensible heat and the latent heat of fusion of water to maintain tree temperatures at or above 0°C. After early failures in development of this approach, it has gained wide popularity in commercial groves in the southeastern United States (Bourgeois and Adams, 1987;Bourgeois et al, 1990;Braud et al, 1981;Nesbitt et al, 2000;Parsons et al, 1991;Rieger et al, 1985). Use of microsprinkler irrigation for young trees to protect the lower trunk is similar in effect to soil banking but easier to implement once the system is established.…”

“…One major limitation of this approach is the need for large quantities of water. In some areas, water is limited, which has stimulated research to identify the minimum amount required to maintain tree survival (Bourgeois and Adams, 1987;Bourgeois et al, 1990;Braud et al, 1981;Nesbitt et al, 2000;Parsons et al, 1991;Rieger et al, 1985). In Alabama, groundwater is currently not limiting in many parts of the southern counties where satsumas are grown.…”

“…Although high-quality fruit can be grown in this region, the principle limitation for long-term production is still the threat of freezes. However, freeze protection measures that did not exist in the early 1900s, especially microsprinkler irrigation (Bourgeois and Adams, 1987;Bourgeois et al, 1990;Braud et al, 1981;Davies et al, 1987;Nesbitt et al, 2000;Parsons et al, 1991;Rieger, 1989;Rieger et al, 1985Rieger et al, , 1986Rieger et al, , 1988aRieger et al, , 1988b and high tunnel plastic houses, are available today that reduce significantly the severity of freeze injury. Furthermore, more cold-hardy cultivars (Zhang et al, 2002) and the potential of genetic modification to enhance cold tolerance (Iba, 2002;Nolte et al, 1997) may reduce the risk of freeze injury.…”

Water-based Cold Protection of Chill-sensitive Foliage Plants in Shadehouses

“…Water-based cold protection of crops has been extensively used in Florida since the1960s (Harrison et al, 1974). Studies in Florida citrus groves have reported the benefits of using water for cold protection (Parsons et al, 1982(Parsons et al, , 1985(Parsons et al, , 1991a(Parsons et al, , 1991b. Research on the beneficial effects of using water for cold protection of other crops grown outdoors such as apples and strawberries has also been conducted (Heinemann et al, 1992;Koc et al, 2000;Stombaugh et al, 1992).…”

Impact of Microirrigation on Florida Horticulture

“…Work in Florida has shown that microsprinklers can, indeed, be effective in major freezes (Oswalt and Parsons, 1981;Parsons et al, , 1982 and are less expensive to install in new groves than solid-set sprinklers. Even when the risk of evaporative cooling was high in low-humidity, windy freezes, microsprinklers provided some protection (Parsons et al, 1985(Parsons et al, , 1991Parsons and Wheaton, 1987). Drip irrigation provided virtually no freeze protection.…”