Rasoul Asadi - PhD student, Water Engineering Department, Faculty of Water and Soil, Zabol University
Farzad Hassan Pour - Associate Professor, Water Engineering Department, Faculty of Water and Soil, Zabol University

A field experiment was carried out over two years to investigate the effects of deficit irrigation applied with surface and subsurface drip irrigation systems on water use efficiency and yield of cotton (Gossypium Hirsutum). The experiments were carried out during 2014-2015, at the Agricultural and Natural Resource Research Institute of Arzu’iyeh, located in Kerman region, southern part of Iran) in a split plot based on a Randomized Complete Block Design (RCBD) with three replications. Treatments considered three levels of irrigation, based on 100 (L1, full irrigation), 80 (L2) and 60 (L3) percent of crop water demand at each irrigation event, as main plots, as well as two drip irrigation methods, including surface (S1) and subsurface (S2), as subplots. All treatments were assessed in terms of yield, water use efficiency, as well as of economical aspects, including investment preference determination. Two-year comparison showed that yield, water use efficiency, boll weight, number of boll and plant height in subsurface drip irrigation system (S2) were increased 10.8, 11, 7.45, 12.8 and 11.2 percent compared to surface drip irrigation system (S1), respectively. In addition, yield, number of boll, boll weight and plant height under 100 percent of crop water demand at each irrigation event (L1) increased 16.4, 14, 9.3 and 15.1 percent compared to 80 percent of crop water demand at each irrigation event, respectively. However, water use efficiency was equal in the two treatments. Economic analysis showed that applying 100 percent of crop water requirement in subsurface drip irrigation (L1S2) was superior to the other treatments. Therefore, it is suggested that full irrigation would be applied in a subsurface drip irrigation system for cotton production in the studied area owing to higher farmers income, higher water use efficiency and less water consumption.

drip irrigation, deficit irrigation, cotton, yield components, water use efficiency