Submitted to: International Journal of Fruit Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/15/2009
Publication Date: 10/1/2009
Citation: Hunt, J.F., Honeycutt, C.W., Starr, G., Yarborough, D. 2009. Influence of coastal proximity on evapotranspiration rates and crop coefficients of Maine lowbush blueberry (Vaccinium angustifolium). International Journal of Fruit Science. 9:323-343. Interpretive Summary: Blueberries have been shown to be one of the most healthful fruits for human nutrition. Irrigation can increase blueberry yield; however, growers need accurate information on the amount of water required by blueberry plants. We measured actual water demand at several locations and showed that it increased with distance from the Maine coast. We also determined how growers can use these values to calculate how much water they should use when irrigating their blueberry crops. This research provides growers with accurate information on blueberry water demand, allowing them to optimize production while reducing water application.
Technical Abstract: Supplemental irrigation can increase lowbush blueberry (Vaccinium angustifolium) yield in humid environments. To best utilize this management technique, growers require accurate knowledge of regional crop water demands. Meteorological data and weighing lysimeters were used to determine Penman-Montieth grass reference evapotranspiration (ETo) rates and actual evapotranspiration (ET) rates of lowbush blueberry at five irrigated and two non-irrigated fields of varying distance from the Maine coast. Mean daily air temperature, relative humidity range and solar flux increased with increasing distance from the coast. Fog contributed 7.2 and 18.3 cm of water at 22.5 km and 0.8 km from the coast, respectively. Four-year mean weekly ETo rates for July, the month with greatest potential water demand, were 2.76 cm/wk, 3.21 cm/wk, 3.52 cm/wk and 4.23 cm/wk for sites located 0.8 km, 6.4 km, 22.5 km and 48 km, respectively, from the coast. Actual ET rates for both crop and prune rotations followed a similar pattern of increasing magnitude with distance from the coast. For July, mean crop and prune year pooled weekly ET rates at 0.8 km, 6.4 km, and 22.5 km from the coast were: 1.69 cm/wk, 2.28 cm/wk, and 2.40 cm/wk, respectively. Standard condition crop coefficient (Kc) values for both rotations during May through September were calculated to be 0.68 for sites 6.4 and 22.5 km from the coast. Thus, it appears that the same Kc value can be used universally within the typical growing range of Maine lowbush blueberry. These findings should substantially contribute to improved water use efficiency for irrigated lowbush blueberry in Maine.