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ESTIMATION OF SOME HYDRAULIC PROPERTIES OF GYPSIFEROUS SOIL USING PEDOTRANSFER FUNCTIONS | ||
| The Iraqi Journal of Agricultural Science | ||
| Article 1, Volume 44, Issue 4, 2013, Pages 518-527 | ||
| Authors | ||
| R. M. Shihab; Q. R. Abdulwahhab | ||
| Abstract | ||
| The objective of this experiment was to evaluate and drive some hydraulic characteristics for gypsiferous soil using Pedotransfer Functions concept (PTFs). Soil samples of different gypsum content were used to measure soil moisture tension curve (SMTC). van Genuchten model (eq.1) was used to fit the SMTC data through obtain best model parameters. Water capillary rise (h) of soil samples were measured for 200 hr and mean effective pore radii (r) were determined (eq.3). Also, r was estimated as a function of θ from SMTC (eq.4) which correlates between eqs.1 and 3. The work also extended to derive eq. 1 to measure hydraulic capacity function [Cw(h)] using RETC software. Results showed that good fitting was obtained between measured and predicted θ of SMTC for all gypsum contents. The values of r calculated from eq.4 increased by 27-104% compared with that calculated from eq.3 for 60 cm height( tension). As well as, r values were higher for all tension and θvalues. Values of Cw(h) were near zero at high water tension, while ranged from 0.0057 to 0.0068 cm-1 at low water tension where the SMTC is nearly level. It reaches a maximum in the capillary region where the slope is steepest. Also, the results of Cw(h) explained that most of the pores have radius equal or slightly larger than 0.15 cm. Cw(h) increased with an increase in the gypsum content, and ranged from 0.019 to 0.027 cm-1. It is obvious that pedotransfer functions use is a developed approach to evaluate the soil hydraulic characteristics where it gave an accepted fitting between measured and calculated values which means it is dependable to describe the concepts of transporting in soil, especially in gypsiferous soil. | ||
| Keywords | ||
| Water capacity functions; Effective pore radius; van Genuchten eq; edotransfer functions; Van Genuchten | ||
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