Freeze and Frost Protection with Aqueous Foam— Foam Development

Abstract

ADDITIONAL INDEX WORDS. freeze and frost damage, plant cold protection, radiation shield, biodegradable aqueous foam, and mulching. SUMMARY.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.

Freeze and Frost Protection with Aqueous Foam— Field Experiments

“…Thus, the foam layers were exposed to the dry outdoor environment for 8 d, with only a minor observed reduction in foam thickness (≈10%), while lateral (length and width) shrinkage was not evident. Its size and resilience were about the same as those of the foam observed in the laboratory (Choi et al, 1999).…”

“…T he development and evaluation of the gelatin-sugarbased aqueous foam was presented by Choi et al (1999). Many possible applications of this long-lasting foam may be found if its effectiveness for cold protection is proven in the field.…”

“…The long-lasting aqueous foam has the potential to act as a superior mulching material when applied directly over the soil. An experiment was conducted (for freeze-frost protection) to measure soil temperatures and determine the effectiveness of foam as a soil mulch (Choi et al, 1999). In addition, two trays of lettuce seedlings were monitored to observe the modification of plant leaf temperature resulting from an application of foam.…”

“…A polyethylene plastic film-covered, hoop-supported row tunnel [1 × 2 × 0.8 m (3.3 6.6 × 2.6 ft, length × width × height] was installed above a side-byside test consisting of foam applied to the ground as a soil mulch and foam applied to a tray of lettuce plants as a plant insulator (Choi et al, 1999). The tunnel provided protection from rainfall, but not from radiative heat loss; i.e., longwave transmission through the polyethylene was ≈80% for a single, noninfrared barrier film (Giacomelli and Roberts, 1993).…”

“…The treatments included two depths of applied foam over soil-thin foam [2.5 cm (1.0 inch)], thick foam [5 cm (2.0 inch)]-and bare ground as a control. At each of these six locations, three thermocouples were located to measure the temperature of the soil near the surface [0.25 cm (0.1 inch)] and at a depth of 2.5 cm (1 inch) (see Choi et al, 1999, for detail locations). The air temperature within the tunnel was measured at 12 cm (4.4 inch) above the bare soil.…”