An evaluation of the temperature conditions inside vine grow tubes on cold nights

Abstract

Young vines are very susceptible to frost damage due to their short height which situates frost-sensitive buds and shoots very close to the ground, which is where the coldest air temperatures typically occur. Farmers often use grow tubes to protect young vines from damage by animals and herbicides, but the potential benefit for protecting vines from frost damage has been less understood. The objective of this work was to evaluate the nighttime temperatures that would be experienced by plant leaf tissues inside grow tubes of two different heights as compared to similar tissues without grow tubes. Leaf temperatures were estimated by measuring the temperature of 2.5 cm x 2.5 cm squares of copper sheet, 0.16 cm thick, painted black, to duplicate the radiation temperature conditions of small grape leaves. These were installed horizontally at heights of 0.15, 0.30, and 0.45 m above the ground, with the following three treatments each replicated three times: 1) No tube, 2) 0.76 m tube, 3) 0.46 m tube. Grow tubes were a rigid, twin-walled plastic material having a light peach color placed directly against the ground surface. The average temperature at 0.15 m was 0.3 °C warmer inside both tube treatments as compared to the no tube treatment. The average temperature at 0.30 m was 0.1 °C warmer inside the tall tube as compared to the no tube treatment, while no difference was observed with the short tube at this height. The average temperature at 0.45 m inside the tall tube was 0.3 °C colder than the no tube treatment, while the average temperature inside the short tube was 1.6 °C colder than the no tube treatment. Thus, at heights close to the ground there was a temperature benefit from the tubes, but this effect diminished with height. At taller heights, particularly where the sensor was near the top of the tube, the estimated leaf temperature was significantly colder than a similar unprotected sensor. This indicates that the large radiating surfaces of the tubes themselves may have important cooling effects on tissues emerging from the tubes.