TY - JOUR ID - 57978 TI - Evaluation of Estimation Methods for Water Field Capacity in Soils of Khuzestan Province JO - Iranian Journal of Soil and Water Research JA - IJSWR LA - en SN - 2008-479X AU - sheikhesmaeili, omid AU - Moazed, Hadi AU - Naseri, AbdAli AD - Y1 - 2016 PY - 2016 VL - 47 IS - 1 SP - 55 EP - 63 KW - Pedotransfer Function KW - Quasi-Empirical Model KW - Soil moisture curve DO - 10.22059/ijswr.2016.57978 N2 - Indirect prediction of hydraulic characteristics of vadose zone is based on their readily available properties in the form of Pedo Transfer functions (PTFs), as a fast and low-cost solution has been widely practiced in irrigation and drainage problems. These studies was aimed at assessing the performance of the conventional methods of estimating soil moisture content at their field capacity (θfc) and introduce the appropriate PTF under laboratory and field conditions in Khuzestan province soils. The buried probes of the Time Domain Reflectometry device (TDR) were inserted at various depths to monitor soil moisture conditions in either of the physical model or experimental field under surface-point source drip irrigation with a discharge rate of 4 lph. Then, the physical soil properties and soil water contents at their specific matric potentials were assessed to determine the hydraulic parameters of Van Genuchten- Mualem (1980) model Throughwith the RETC program. The results of the research to evaluate the performance of several well-known Point-PTFs indicated that the quasi-empirical models as based upon physical principles can be a proper alternative to traditional methods for estimating θfc on the condition of having been tested on the field. So that, the PTF of Twarakavi et al. (2009) with indices of NRMSE (3.1%) and SE (0.51%) could closely predict θfc more accurately than either the Rosetta (2001) artificial neural network approach which presented the values of NRMSE (5.2%) and SE (0.71%), or the Dexter (2004) equation with the values of NRMSE (9.7%) and SE (1.75%). However, there were no differences observed in the indicator of Model Efficiency (ME) for each of the three PTFs. Based on the assessment rresults of these PTFs, the negative effects of soil compaction and the level of sand on the θfc were clearly shown using one-way ANOVA (p < 0.05). On the contrary, the levels of clay and silt exerted positive significant (p<0.05) increasing effects on  θfc . UR - https://ijswr.ut.ac.ir/article_57978.html L1 - https://ijswr.ut.ac.ir/article_57978_902674bc8cb839092425597112a595d2.pdf ER -