Water dynamics in drip and overhead sprinkler irrigated potato hills and development of dry zones

irrigation scheduling and nitrogen fertilizer placement and time of application have been studied extensively in an attempt to maximize utilization efficiency of nitrogen by potato (Solanum tuberosum L.) plants and reduce nitrate leaching to groundwater. Some researchers believe that drip irrigation, as compared to sprinkler irrigation, is more efficient in supplying irrigation water to potato hills. To investigate water distribution and movement through potato hills under drip and sprinkler irrigation time domain reflectometry (TDR) probes were installed into potato hills to monitor water content at 15-min intervals at various positions in the potato hill. On average, water content values within the centre of the potato hill were greater under drip irrigation (average for 1996 and 1997 was 0.104 and 0.110 m(3) m(-3), respectively) as compared to sprinkler irrigation (average for 1996 and 1997 was 0.085 and 0.066 m(3) m(-3), respectively) where similar amounts of irrigation water were applied weekly. Water content values in the centre portion of the potato hill, where the greatest densities of roots occur, were greater under drip irrigation than sprinkler irrigation by an average of 0.032 m(3) m(-3) for values averaged over the two growing seasons. Concurrently, water content values were less in the furrow of drip irrigation than sprinkler irrigation by an average of 0-025 m(3) m(-3). Decreased water content in the centre portion of the potato hill under sprinkler irrigation became more prominent as the growing season progressed, resulting in hydrophobic soil conditions midway through the growing season. Copyright (c) 2007 John Wiley & Sons, Ltd.