Microclimatic Factors Associated with Enhanced Plant Growth Under Rowcover

Studies in plasticulture have associated growth with increased temperatures, but plant-water relationships have been overlooked. Studies with spun-bonded rowcover were conducted in Mississippi and the U.S. Virgin Islands to associate microclimatic parameters with plant growth. In Mississippi, rowcover is used in early spring to raise temperature and promote growth in sweetpotato. In our study at the Pontotoc Research Station, rowcover and black plastic mulch increased the mean air temperature by 6.5^oC, but the maximum air temperature was 45.5^oC, 20^oC higher than without rowcover. In sunny days the temperature reached 50^oC and over for most of the day suggesting extreme stress. In contrast, relative humidity was the same, daily solar radiation decreased in 25% and wind was undetectable under the rowcover. These microclimatic changes reduced the evapotranspiration under the rowcover to 44% and doubled plant growth. While rowcover is used only as an insect barrier in the U.S. Virgin Islands since daily temperature ranges between 23^oC and 33^oC, the response in plant growth was similar. Rowcover increased mean temperature by 1.5^oC only and the maximum temperature averaged 38.4^oC, 5.1^oC higher than that without rowcover. Similar to Mississippi, solar radiation decreased in 28% and wind was also undetectable under the rowcover reducing evapotranspiration to 58% of the uncovered control. In addition, plant growth doubled under rowcover. Therefore, rowcover reduces water stress also resulting in more favorable conditions for plant growth.