Jalal D. Jabro, William M. Iversen, Robert G. Evans, William B. Stevens and Brett L. Allen, USDA-ARS, Sidney, MT
A study was designed to complete two full rotation cycles of a three-year rotation of sugarbeet, malt barley and potato under a linear-move self-propelled sprinkler irrigation system. The irrigation frequencies were: the high frequency (HF) irrigation, which entails applying small irrigation quantities at high frequency while the low frequency (LF) irrigation is applying large irrigation quantities at low frequency. Irrigation frequency was varied based on either 15mm (HF) or 30 mm (LF) cumulative crop evapotraspiration replacements. Seasonal crop water use (CWU) amounts were determined using the water balance equation of sugarbeet, malt barley and potato under HF and LF irrigations for 2007, 2008, 2009, 2010 and 2011. Statistical analysis demonstrated that no significant differences due to irrigation frequency were found for yield, CWU, and crop water productivity (CWP) of sugarbeet, malt barley or potato. Small differences in CWU values between HF and LF irrigations are due to variations in soil moisture content in the soil profile and drainage losses below the 0.91 m soil depth. Traditional LF irrigation thus can sustain economic yield production, improve water use and reduce net economic input as feasibly as HF irrigation practices when a self-propelled automated sprinkler system is used on a sandy loam soil.