Cold Protection of Leatherleaf Fern in Shadehouses Using Water and Crop Covers
Six shadehouses were used in tests of irrigation rates and crop covers for cold-protecting leatherleaf fern [Rumohra adiantiformis (Forst) Ching]. Each shadehouse was equipped with two irrigation systems—one over-the-crop to supply heat and one over-the-shadehouse to supply water for sealing the openings in the shade fabric with ice. The over-the-crop irrigation system consisted of frost protection wedge-drive impact sprinklers providing water application rates of 0.30, 0.56, and 0.76 cm/h. Six-m × 9-m spunbonded polypropylene crop covers weighing 20 and 51 g·m–2 were tested. During radiation freezes, all water application rates protected immature fronds from damage. Damage during advective freezes decreased with increasing water application rate, but, even when crop covers were used in conjunction with irrigation, some damage still occurred. Temperatures under the lighter-weight cover were higher than under the heavier-weight one, probably because more water passed through the lighter cover to the crop. Water application rates had no effect on frond yield.