In this study two methods of measuring saturated hydraulic conductivity namely: Guelph permeameter and Tension Disc infiltrometer were compared in the experimental field of Moghan Faculty of Agriculture containing Sandy-loam soil texture. Guelph experiments were performed by using Guelph penetrometer model k2800. In this regard, 15 boreholes each with 5 cm diameter and 25 cm depth were drilled in a grid of 2×2 m and Discharge was measured at the hydraulic heads of 5and 10 cm. Experiments were performed based on completely randomized design with 4 treatments and 15 replicates. Also in the Tension Disc infiltrometer, determination of saturated hydraulic conductivity was performed on the same grid with 5, 10, 15 cm suction heads. The average hydraulic conductivity obtained for Tension Disc infiltrometer, Guelph permeameter in 5, 10 cm of hydraulic heads and Guelph two depths analysis was found to be 7, 3, 4, 6.2 cm per hour, respectively. Results of Fisher test revealed that all methods are classified in a group and not significantly different from each other at the 0.01 level and beyond, Average values for the inverse of macroscopic capillary length parameter was obtained to be 0.07 cm-1 and as the value of saturated soil hydraulic conductivity increased, an increase in the value of inverse macroscopic capillary length parameter was observed.

Estimation and modeling of non-saturated hydraulic properties of the soil is an effective approach to accelerate and facilitate studies on the movement of water and salts in the soil. In this paper, an inverse solution estimation method was used to analyze the results obtained by disk infiltrometer tools. Also, Wooding analytical method and Hydrus-1D software were used to simulate infiltration values and hydraulic properties. In this regard, four lysimeters were used and infiltration experiments were carried out at suctions of 15, 6, 3 and 1 cm. Also, pressure data were recorded by four tensiometers installed in the lysimeters. Finally, the results of the inverse solution method were compared with the Wooding method. The results showed that the inverse solution method was generally in good agreement with the Wooding analysis method. The inverse solution method estimated the unsaturated hydraulic conductivity values close to Wooding method at low suctions, but the estimated values were greater 12% than the Wooding method with increasing suctions.

The macroscopic capillary length (λc) is a key parameter to use golf permemeter, double rings, and the tension infiltrometer. The value of this parameter indicates the predominance of gravitational potential over capillary potential. In this study, the field method of tension infiltrometer was used in both forest and agricultural in loamy-sand texture in Moghan Faculty of Agriculture. In order to perform the tension infiltrometer method, the experiments carried out in 5, 10 and 15 (cm) matric suctions at 20 points in the form of a regular square network with 3*3 m distances in forest and farm land uses and infiltration data was modeled usingWooding's analytical method (best fit) and was obtained macroscopic capillary length for each land uses. The mean macroscopic capillary length and the saturareted hydraulic conductivity (Ks) for forest and farm land uses were obtained 9.4, 9.5 (cm) and 1.7, 6.7 (cm/hr), respectively. Also, in terms of sorptivity, S(h) and steady-state flux, q(h) in the applied matric suction, the values obtained for farm use were significantly higher than forest use values and its decreasing trend was seen from 5 to 15 suction, especially in farm use. The mean values of sorptivity, S(h) and steady-state flux, q(h) in applied suctions and in farm land use were calculated 1.2 and 1.6 times more than forest use, respectively. Performing Compare Means test at the level of 1% showed a significant difference between the two land uses in all indicators except for the macroscopic capillary length.

In order to evaluate the effect of tillage depth and speed on soil physical and hydraulic properties, this research was performed in a clay loam soil. Moldboard plow treatments in three replications were employed in a completely randomized block design with a split tape according to both speed and depth of tillage. Infiltration of soil was determined in undistributed samples by using Disc infiltrometer apparatus under-15,-6,-3 and 0 cm H2O suctions (K15, K6, K3, Ks). The results revealed that the tillage speed had significant effect on K3 and Ks at 5% and 1% probability level, respectively, whereas deep tillage as well as interaction of the factors did not affect them. Both of the studied factors (depth and speed) and their interaction had no significant effect on K6 and Gardener α coefficient, while they had significant effect on the bulk density of top soil at 5% probability level. Furthermore, K15 showed significant differences under the effect of tillage depth at 5% probability level. The results also indicated that speed of tillage had no effect on the bulk density of sub-surface layers.

Hydraulic conductivity (K) of unsaturated and saturated soils and the pore size distribution parameter (Gardner a) are important hydraulic parameters for understanding some aspects of unsaturated soil water flow. These parameters vary with time as well as spatial position. For To investigate these changes, field measurements were performed using Disc infiltrometer at matric potentials of -15, -10, -6, -4, -3, and 0 cm water were in three times periods from June to August in 2009. The measurements were made in four fields under different land uses as including winter barley, silage single cross corn, apple orchard, and uncultivated land in the agricultural fields of Urmia University, Iran. Five replicate sequences of infiltration rate tests were conducted for each measurement set and land use. Soil texture at these sites was classified as clay. The study was conducted employing split plot in time experiment. Results of ANOVA showed that land use, time period, and their interaction had significant impact (at one per cent level) on K values (except at matric potential of -15 cm). At matric potential of -15 cm, the average K displayed significant variation (at five per cent level). Therefore, land use and time period showed the least impact on K15. Values of Gardner a had significant differences (at one per cent level) with respect to land use and time, but showed no significant difference (at five per cent level) with respect to their interaction. Results of this study showed that the initial soil moisture had an important role on the rate of temporal variation of soil k.

Introduction: In recent years, to increase the efficiency of surface irrigation methods, new techniques such as surge irrigation have been developed. Numerous studies have shown that the surge flow can reduce water consumption in the advance phase and subsequently improve irrigation efficiency and water distribution uniformity. One of the factors affecting the performance of surface irrigation systems is the accurate estimation of infiltration. Due to continuous changes in the infiltration process during on-off cycles in surge irrigation, determining the empirical equation of infiltration in surge irrigation method is complex and requires timeconsuming and costly field data. As a result, proper selection and parameterization of empirical equations with a simplified procedure are needed. The goal of this research was the field evaluation of the point method (surge infiltrometer) to simulate the infiltration process in advance phase surges. Materials and Methods: A field experiment was conducted at the experimental station of the College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran. A ring infiltrometer was modified by connecting a pipe arm for inward and outward water flow to the ring and from the ring to the pipe to create onoff surge cycles, respectively. Water entered the ring through the inlet hole at the top of the pipe arm and water depth was recorded at different time intervals during the on-time of each cycle. Four treatments were performed for infiltration tests under surge flow, including different cycle time and ratio. Also, infiltration tests were performed under continuous flow conditions. To simulate the first (dry soil) and second irrigation conditions, infiltration experiments were conducted twice on an 8-day interval. The Kostiakov infiltration equation was corrected by applying surge factors to predict infiltration water depth for subsequent surges, using first surge data. The empirical coefficients of the Kostiakov equation were calculated by applying the two-point technique. Results and Discussion: Results of the study revealed that the infiltration data simulated by the developed Kostiakov equation matched closely with those collected from the surge-ring infiltrometer. The coefficient of determination and the root mean square error were calculated to be 0. 92 to 0. 97 and 0. 03 to 0. 16 cm, respectively. In general, the amount of cumulative infiltration in the second and subsequent surges decreased. The ratio of the infiltration depth at the end of the second to the first surge was less than 0. 5. In all experiments, the depth of water infiltrated in the third surge was significantly reduced and almost reached to the final infiltration rate. As the cycle ratio increased, the cumulative infiltration also increased. However, the effect of on-off time on the infiltrated water depth in the first experiment was greater than that in the second experiment. It was concluded that in the first experiments, the surging phenomena substantially reduced water movement and the reduction in cumulative infiltration ranged from 50 to 70% during the second surge and from 59 to 85% during the third surge. The above values were determined 52 to 76% and 61 to 88% for the second experiment, respectively. A significant difference was observed between surge and continuous flow tests. The surge flow led to a 46 to 76% reduction in the cumulative infiltration depth compared to the continuous flow. The effect of surge flow was greater in the first experiments. Conclusion: One of the most important points in designing surface irrigation systems is to determine the infiltration equation parameters. In particular, the difficulty involved in the planning and design of surge irrigation systems is the prior knowledge and understanding of how infiltration changes occur during surging. The main objective of the present study was to evaluate the surge ring infiltrometer test to predict the infiltration in the second and third surges using the first surge data. The results obtained from the surge infiltrometer experiments showed that the use of surge irrigation has the potential to reduce infiltration. The observed and predicted cumulative infiltration for the second and third surges showed a good agreement. The surge-ring infiltrometer has the potential for creating an on-off mechanism and is best suited to determine the cumulative infiltration from surges for constant on-off time surge intervals.

Zhang's method can be used to analyze the unsteady state flow of water in the soil. The aim of this study was determining a suitable method for estimating the amounts of saturated and unsaturated hydraulic conductivity in pasture, orchards, and other agricultural land uses and how it is affected by land use change. Originally, many orchards and cropped lands were pasture land. Field infiltration rate experiments were conducted using tension Disc infiltrometer at tensions of 0, 3, 6, 10 and 18 cm of water with three replications for each land use. Hydraulic conductivity values for different land use were determined by Zhang method. To estimate hydraulic parameters of Van Genuchten soil hydraulic conductivity model in Zhang's method, Rawls et al. and Carsel and Parrish databases, extracted results of ROSETTA code and HYDRUS-2D software were used. HYDRUS-2D inverse modeling method, also, was used to estimate soil hydraulic properties. Relative Error (RE) and root mean square error (RMSE), as statistical parameters were used to evaluate the estimated hydraulic conductivity versus the measured one. Statistical parameters values showed that, in all the three land uses, Zhang model based on Carsel and Parish had the least amount of RE and RMSE and the highest accuracy in estimating the hydraulic conductivity values. In all land uses, other methods (except Carsel and Parrish) performed weakly at low tensions, but results improved at high tensions. During the land use changefrompasturetoorchardandfield crops, saturated hydraulic conductivity valuesincreaseddue toanincrease in soil organic matter in orchards and cropped lands.

HYDRUS2D/3D software was empolyed to estimate the hydraulic parameters of van Genuchten-Mualem model via inverse modeling using double-ring infiltrometer’ s data (within 3 different soil textures). Nine scenarios of inverse modeling (divided in three groups) were considered with different numbers (5, 4 and 3) of fitted hydraulic parameters for optimization. In the first group, simulation was carried out solely using cumulative infiltration data. As for the second group, cumulative infiltration data plus water content at h = − 330 cm (Field Capacity, FC) were taken as inputs. In the third group, cumulative infiltration data plus water contents at h = − 330 cm (FC) and h = − 15000 cm (Permanent Wilting Point, PWP) were simultaneously taken as predictors. The results indicated that by reducing the number of hydraulic parameters, involved in the optimization process, simulation error would be reduced and the accuracy of prediction of other soil hydraulic parameters enhanced. Including FC as an additional data was important to more accurately optimize/define soil hydraulic functions. So, the use of (Saturated hydraulic conductivity) Ks, (Shape parameter of soil water characteristic curve) n and (the parameter, inversely related to the air entry value) a, as predictor parameters and FC as additional data constituted the most appropriate scenario. RMSE(cm3), NRMSE, AIC, and R2 were respectively estimated 1259, 528. 2, 0. 0081 and 0. 9999 in Sandy Loam soil, 242, 79. 0, 0. 0059 and 0. 9988 in Loamy soil plus 298, 153. 6, 0. 0174 and 0. 9983 in Salty Clay soil. Taking into account PWP as additional data increased the simulation error in all the 3 soil textures.

As one of the main indicators of soil quality, structure is related to hydraulic parameters which plays a significant role in predicting and estimating them (Pachepsky et al., 2008). Mohawesh et al, (2017) stated that hydraulic properties are key factors in the movement of water and the transport of pollutants, and the soil structure has a significant effect on the storage and movement of water in the soil. Tension infiltrometer is an effective tool to measure infiltration rate and the flow of water into pores using suctions less than 0 cm, where the macro and meso pores have highest rate of hydraulic activities for water and solution transportation. The measurement of hydraulic conductivity in different suctions is important for characterizing different aspects of unsaturated and near-saturated water in the soil. Although the hydraulic properties of the soil have been investigated from different aspects and by different methods, the role of soil structure specifically from comparison viewpoints of different types of structures and their effects on hydraulic properties has not yet been studied. The aim of this study was to measure and evaluate the hydraulic properties and quantitative parameters describing the water conductive active pores using tension infiltrometer in near-saturated condition of different soil structures.