USING CANOPY TEMPERATURE, SOIL TENSION AND MOISTURE MEASUREMENTS AS TOOLS IN CRANBERRY IRRIGATION
Canopy temperature based measurements have been used in other crops as a tool in irrigation management. Cranberry (Vaccinium macrocarpon) is well-suited to a canopy-temperature-based technique because it is a perennial crop that retains a leafy canopy year-round. A potential drawback with this approach in cranberry could be the fact that stomata in cranberry leaves never open widely, as they do in other plants. This apparent handicap can be removed by using a combination of canopy temperature measurement concurrently with soil moisture measurements. The objective of this study was to use a combination of canopy-air temperature differential, soil tension and volumetric water content to determine when cranberry plants are experiencing water stress. A combination of (i) infrared K type thermocouples (IRT), (ii) wireless tensiometers, and (iii) volumetric water content sensors were connected to a Campbell CR 1000 data logger on a (i) sand based bog and (ii) peat based bog positioned side by side. Canopy-air temperature differentials (Tcanopy-Tair) were calculated from collected IRT data and vapor pressure deficit (VPD) were determined. Regression analysis was used to develop linear relationships between these two variables from daytime readings on clear days with no cloud cover. Also, a relationship between moisture content and tension was derived using non-linear regression techniques. Zone of saturation, when all air pores are filled with water, was reached at about 30% volumetric water content. This volumetric water content corresponds to a soil water potential of -2 kPa. In our research, field capacity was reached at 10% water content corresponding to a soil water potential of -5 kPa in sand, and 15% water content corresponding to a soil water potential of -4.5 kPa in peat. Cranberry plants grown on sand based subsurface tended to experience more water stress than those grown on a peat subsurface based on canopy-air temperature differentials, soil moisture content and soil tension.
Jeranyama, P., DeMoranville, C. and Waddell, J. 2014. USING CANOPY TEMPERATURE, SOIL TENSION AND MOISTURE MEASUREMENTS AS TOOLS IN CRANBERRY IRRIGATION. Acta Hort. (ISHS) 1017:487-492
Vaccinium macrocarpon Ait., water stress, volumetric water content, peat, sand