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Aqueous foam was developed to serve as a barrier to conductive, convective, and radiative heat transfer. Through the use of a bulking agent, the physical properties of gelatin-based foam were more stable, adhesive, biodegradable, and long lasting. The phytotoxicity, possible environmental hazard and removal of the foam were also considered. Resistance to freezing–thawing, heating–evaporation, and wind were evaluated. Studies to determine the foam’s long-term stability under field weather conditions were completed. The handling and performance characteristics of the foam necessary for development of this application were determined. Factors that affect the physical properties and the utilization of the foam were quantified. These included the proportions of the foam components, the mixing temperature of the prefoam solution, the application temperature, and the rate of foam generation. The newly developed foam might be ideal for freeze and frost protection in agriculture. F reezes occur due to convective heat loss during windy and severe cold periods, while frosts are due to radiative heat loss to the cold sky during calm, clear nights. In general, freeze–frost damage takes three forms: 1) immediate damage—the current yields cannot be marketed, and/or foliage is damaged, 2) long-term damage—replacement of badly damaged perennial crops such as orchard or grove trees delays production for several years, and 3) risk avoidance damage—farmers whose land would otherwise support higher-income frost sensitive crops do not plant them for fear of loss. In the United States, freeze–frost damage is common in many states every year, and sometimes it occurs repeatedly. For example, successive cold damages occurred in January 1981, January 1982, December 1983, and January 1985 in Florida (Polopolus and Gunter, 1985). In particular, the monetary losses due to the 1983 freeze were estimated to be more than $2 billion dollars in Florida alone. The same freeze also decimated much of the citrus (Citrus L.) acreage in Texas the day before the Florida damage. The recurring widespread losses of agricultural commodities due to freeze–frost damage have been the driving force behind the continued research in crop protection during the last few decades. In cases where the cold period is severe and prolonged with a danger of freezing, the existing techniques are either inadequate to protect trees or too costly (Reiger, 1989). Therefore, any effective, economically viable, environmentally responsible means of protection against freeze and frost damage by elevating temperatures by only a few degrees may be of inestimable value to the agricultural industry in the United States and around the world. There have been many cold protection techniques used such as artificial wind or heat generation, or the use of phase change energy from spray irrigation water. One alternative is the application of aqueous foam over crops for both freeze and frost protection. The scientific justification for the present research is 2-fold: 1) aqueous foam is a good insulator with relatively low thermal conductivity, and 2) aqueous foam is an excellent radiation shield, since water is opaque to radiation. Previous agricultural foam reThe cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

Freeze and Frost Protection with Aqueous Foam— Foam Development