Impacts of using polyethylene sleeves and wavelength-selective mulch in vineyards. I. Effects on air and soil temperatures and degree day accumulation

Effects on soil and air temperatures of wavelength-selective polyethylene mulch applied in planted rows, and clear polyethylene enclosures (sleeves) applied around vine canes or cordons for 7 wk in the spring were determined in three Merlot vineyards in the Okanagan Valley, British Columbia. Three sleeve configurations were studied: single-layer and closed at bottom; single-layer with bottom ventilation added after 5 wk; and double-layer with bottom ventilation added after 5 wk. All sleeve's were perforated at the top between two supporting trellis catch wires, and were stapled closed at the bottom under the cordon or cane. Sleeve removal was either all at once or in two stages by first opening the top then removing the sides 6 d later. The sleeves increased mean air temperatures by ca. 1 to 2degreesC and maximum temperatures by ca. 5 to 8degreesC, and decreased minimum temperatures by ca. 1 to 2degreesC, depending on the vineyard, measurement period, and sleeve configuration. Adding bottom ventilation to sleeves increased the mean minimum nighttime temperature by ca. 1degreesC at one vineyard but had no effect at the other two sites. Degree day (base 10degreesC) accumulation inside sleeves was 1.5 to 2 times that of ambient, depending on the site, which increased total degree day accumulations for the season by 4.1 to 7.9%. The polyethylene mulch increased soil temperatures by ca. 2degreesC continuously over the diurnal period at two of the vineyards, but at the third where there was significant weed growth under the mulch the increase was less and only at night.