EFFECT OF SOIL WATER POTENTIAL THRESHOLD FOR IRRIGATION ON CRANBERRY YIELD AND WATER PRODUCTIVITY

As the cranberry industry implements irrigation automation, thresholding based on real-time monitoring of soil moisture to initiate irrigation is lacking. This study was conducted to determine the optimum soil water potential for starting sprinkler irrigation (SWPI) that would optimize water productivity (WP) without decreasing yield. During the 2011 and 2012 growing seasons, three sites in Quebec and one site in Wisconsin were equipped with tensiometers, flowmeters, and weather stations for testing wet (-5.5 kPa), dry (-7.0 to -10.0 kPa), and control (-6.0 to -6.5 kPa) treatments. The experimental designs were developed to evaluate the impact of irrigation treatments on yield and WP Dry treatments required 21% to 93% less irrigation water than the control treatments; wet treatments needed 54% to 186% more irrigation water than the control treatments. Irrigation treatments had no significant effect on yield when SWPI values ranged from - 5.5 to -8.0 kPa; however, a significant yield reduction of 11% was observed for a SWPI value of -10.0 kPa. The WP values in dry treatments were always higher than those in control and wet treatments. Dry treatments, with SWPI ranging from - 7.0 to -8.0 kPa, significantly improved the water productivity without decreasing yield.