Irrigation as a Tool for Frost and Freeze Protection Essay -- Agricult

For years now farmers and researchers have understood the value of applying water to crops during periods when the temperature drops below 32oF (0oC). The temperature of 32oF is the freezing point of water and is the temperature at which crops start to become damaged due to the formation of ice crystals in their tissue cells. The point that this starts to occur is considered the crops critical temperature. The critical temperature usually is slightly lower than the freezing point of water and depends on the duration at the temperature. For example, in citrus the critical temperature at four hours is 28oF. This means that a citrus tree can stand a temperature of 28oF for four hours before sustaining damage. After four hours the damage is proportional to the time that the temperature remains below the critical temperature. Temperatures below 28oF for a short period of time (one or two hours) will cause only minimal damage. Temperatures over 28oF can be tolerated for extended periods of time with only minor damage (partial leaf burn, partial defoliation, etc., but no wood damage). Other factors such as stage of growth (if the plant is in early stages of growth or mature), fruit set (whether the crop is still on the plant or not), dormancy (whether the plant is actively growing or is dormant), plant water content (whether the plant is under water stress or not) and overall plant health will influence the critical temperature for a specific crop. There are three ways that water can transfer heat for freeze protection. The first way is through radiation. Water pumped from wells will be introduced into the field at a much higher temperature than the surrounding air temperature (in Florida the temperature for water coming from a well is... ...rmittent coverage. References Hochmuth, G.J., S.J. Lacascio, S.R. Kostewicz, and F.G. Martin. 1993. Irrigation Method and Rowcover Use for Strawberry Freeze Protection. J. Amer. Soc. Hort. Sci. 188(5):575-579. Miller, F. 1977. College Physics. Harcourt Brace Jovanovich, Inc. New York. Parsons, L.R., and T.A. Wheaton, 1987. Microsprinkler Irrigation for Freeze Protection: Evaporative Cooling and Extent of Protection in an Advective Freeze. J. Amer. Soc. Hort. Sci. 112(6):879- 902. Parsons, L.R., T.A. Wheaton, N.D. Faryna, and J.L. Jackson. 1991. Elevated Microsprinklers Improve Protection of Citrus Trees in an Advective Freeze. Hortscience. 26(9):1149-1151. Rieger, M., F.S. Davies, and L.K. Jackson. 1986. Microsprinkler Irrigation and Microclimate of Young Orange Trees During Freeze Conditions. Hortscience. 21(6):1372-1374.