INFLUENCE OF DIFFERENT IRRIGATION METHODS AND IRRIGATION LEVELS ON WATER USE EFFICIENCY, YIELD, AND YIELD ATTRIBUTES OF SWEET POTATOES

This study examines the effects of irrigation methods and irrigation levels on sweet potatoes under field conditions in the Eastern Mediterranean region of Turkey. The experimental treatments included two irrigation methods and four different irrigation levels: blocked-furrow (BF) and drip (DI) irrigation. The irrigation levels were full irrigation (IR100), 66% of full irrigation (IR66), 33% of full irrigation (IR33), and not irrigated (IRO) treatments. Total of 11 irrigation applications were made at weekly intervals throughout the season. The blocked-furrow and drip irrigation both received the same amount of irrigation water. The full irrigation treatment received (IR100) 798 mm of water, and was followed by the treatments of IR66 and IR33, receiving 631 and 471 mm of irrigation water, respectively. The range of evapotranspiration (ET) recorded under BF treatment was 360-691 mm; whereas it was 360-691 mm with DI treatments. Tuber yields showed a wide range of variation as 11.94-51.09 t ha(-1). The significant (P<0.01) yield differences were recorded among the different irrigation methods and irrigation levels. It was noted that tuber yield under DI was 13% higher compared to BF. The irrigation water use efficiency (IWUE) and water use efficiency (WUE) ranged from 36.8 to 65.7 kg ha(-1) mm(-1) and from 33.2 to 75.9 kg ha(-1) mm(-1), respectively. The yield reduction recorded when deficit irrigation was imposed under DI (i.e., D33, D66) was proportionally lower, therefore given higher water use efficiency, than with BF.