TY - JOUR ID - 66321 TI - Determination of subsurface drainage spacing using field data in paddy fields of Guilan Province JO - Iranian Journal of Soil and Water Research JA - IJSWR LA - en SN - 2008-479X AU - Alizadeh, Maryam AU - Afrasiab, Peyman AU - Yazdani, Mohammad Reza AU - Liaghat, Abdolmajid AU - Delbari, Masoomeh AD - PhD/ university of zabol AD - head of the Faculty of Soil and Water Zabol AD - Assistant Professor/Rice Research Institute of Iran AD - University of tehran AD - Scientific staff/ University of Zabol Y1 - 2018 PY - 2018 VL - 49 IS - 3 SP - 607 EP - 617 KW - Subsurface Drainage KW - Drain Spacing KW - Second Crop KW - Steady Equation DO - 10.22059/ijswr.2017.234501.667690 N2 - Subsurface drainage is constructed in the paddy fields with the purpose of drying of land at the time of rice harvest, mid-season drainage and lowering water level after the rice harvest. Most drainage equations have been developed for non-paddy land. However, given the unique special conditions of paddy fields in Guilan province (due to heavy textured soils with low permeability, heavy rain and shallow impermeable layer) compared to non-paddy lands, therefore introduced the equation that is most compatible with these conditions. So in this study, steady and unsteady equations were evaluated in estimating space of subsurface drainage for a second crop after rice harvest. Drainage treatments included: six conventional subsurface drainage systems including drainage system with drain depth of 0.8m and drain spacing of 7.5m (L7.5D0.8), drain depth of 0.8m and drain spacing of 10m (L10D0.8), and drain depth of 0.8m and drain spacing of 15m (L15D0.8), drain depth of 1m and drain spacing of 7.5m (L7.5D1), drain depth of 1m and drain spacing of 10m (L10D1), and drain depth of 1m and drain spacing of 15m (L15D1). From the rainfall occurred during the experiment, a three-day rainfall with a mean value of 23.9mm was selected for decision on the best equation. The equation that estimated the drainage space in the above rainfall with the least deviation from the best drainage treatment was chosen as the best drainage equation. The results showed that Ernst- Hooghoudt equation and Bouwer and Van Schilfgaarde equation combined with Hooghoudt equation estimated drainage space with the least deviations from the best drainage treatment (L10D0.8) and were selected as the best equations in the second cultivation season and the Delroix equation was introduced as the weakest equation in the design of subsurface drainage for paddy field in order to provide suitable conditions for the second cultivation. UR - https://ijswr.ut.ac.ir/article_66321.html L1 - https://ijswr.ut.ac.ir/article_66321_5a5b9e487a191164a2bff328101d8a00.pdf ER -