Determination of Sorptivity, Infiltration Rate and Hydraulic Conductivity of Loamy Sand using Tension Infiltrometer and Double-Ring Infiltrometer

This study was conducted to assess the effectiveness and accuracy of tension infiltrometer (TI) over double ring infiltrometer (DI) for determining infiltration rate (I) of loamy sand. Sorptivity (S), infiltration rate and hydraulic conductivity (K) are soil properties that govern the rate of entry of water into the soil and its movement within the soil. The ease and accurate measurement of these properties depend on the instruments used. DI operates by ponding water and could be affected by preferential water flow during infiltration test which could not be avoided especially on a fertile soil. DI and TI at water potentials of -0.02, -0.04, -0.05 and -0.06 m were used to determine infiltration rate of the soil. The mean values of sorptivity for DI and TI at water potentials of -0.02, -0.04, -0.05 and -0.06 m were 847.02, 63.50, 33.15, 29.90 and 19.46 mm/h1/2, respectively. Mean values of infiltration rates for DI and TI at -0.02, -0.04, -0.05 and -0.06 m water potentials were 471.26, 176.84, 73.73, 71.32 and 37.73 mm/h, respectively. Mean values of hydraulic conductivity for DI and TI at -0.02, -0.04, -0.05 and -0.06 m were 344.45, 22.42, 18.61and 16.83 mm/h, respectively. DI required 100-150 litres for the infiltration test, difficult where water is very scarce and gave higher values of infiltration rate. TI saved water (2-3 litres), controlled preferential water flow and values of S, I and K were within the range obtained by other researchers. TI is more effective for measuring hydraulic properties soil than DI.Keywords:Double ring infiltrometer, tension infiltrometer, sorptivity, infiltration rate, hydraulic conductivity

Estimation of tropical soils’ hydraulic properties with inverse method and tension infiltrometer field data

In the last few years, many studies have been published by authors from several countries offering approximations and use of the inverse method. However, the unique environmental conditions and distinct properties of the tropical soils in Brazil require extra considerations and the need to adjust these methods to tropical soil conditions. Considering the above, this determined the parameters of the van Genuchten (1980) model (θs, θr, α, n) of the water retention curve in the soils. It also determined the parameter (Ks) of the soil’s hydraulic conductivity curve by solving an inverse problem using the HYDRUS-2D model, considering cumulative infiltration data collected in the field by means of an infiltration test using the tension infiltrometer. It then compared the hydraulic properties determined by these methods in relation to the standard laboratory method. The inverse method was able to efficiently determine the water retention curves in the soils here studied; however, it was not possible to reliably determine the unsaturated hydraulic conductivity curve.

Characterization of preferential flow in soils near Zarqa river (Jordan) using in situ tension infiltrometer measurements

Background The Zarqa River (ZR) is located in the northern part of Jordan and supplies King Talal Dam (KTD). The streamflow that discharges into KTD is composed of treated wastewater from the Khirbat Es-Samra water treatment plant (KTP) and runoff generated during the winter season. Thus, during the summer, the streamflow of the ZR is dominated by effluent from the KTP. Due to the severe scarcity of water in Jordan, a portion of the streamflow is utilized for irrigated agriculture in the ZR valley, located between the KTP and KTD. The groundwater in the vicinity of the ZR is vulnerable to contamination—a risk that may be exacerbated by the potential occurrence of preferential flow (PF). Therefore, the PF in the soils near the ZR should be carefully considered. Methods The macropore flux fraction (Qmacro) and macroscopic capillary length (λc) were determined from in situ measurements using a tension infiltrometer equipped with an infiltration disc with a diameter of 20 cm. The macropore was defined as the pore size that drains at a tension of less than —-3— cm. The λc less than 80 mm was considered to be an indication of PF. The measurements were taken at 69 sites along the ZR between the KTP and KTD. At each measurement site, the soil organic matter content (OM) and soil texture were determined using a composite soil sample obtained by excavating the soil beneath the infiltration disc to a depth of 10 cm. Results The data was split into two groups: the matrix flow group (MF), which includes data associated with λc > 80 mm, and the PF group, which includes data associated with λc < 80 mm. The Qmacro values of 0.67 and 0.57, respectively, for PF and MF were significantly different at p < 0.01 (t-test). The flow rates at h=0 were generally well associated with λc, as attested to by a significant difference between the averages of PF (57.8 mm/hr) and MF (21.0 mm/hr) at p < 0.01 (t-test). The OM was positively associated with PF. This was statistically confirmed by a t-test at p < 0.01. The average sand and clay contents of PF and MF were not statistically different. Analysis of the ratio of Soil Organic Carbon (SOC) to clay showed that the average SOC/clay of the PF (14%) was larger than that of the MF (13.3%). After the exclusion of soils with clay content less than 8%, the differences between the SOC/clay averages of PF (9.8%) and MF (7.5%) were significant at p < 0.05, as shown by a WM-test. Conclusion The OM was positively associated with PF. Soil texture—and clay content in particular—influenced the λcvalues. However, the association of clay content with PF was not statistically significant. Consideration of the SOC/clay ratio showed that the tendency toward PF increases as the complexation of the clay content increases. This was most obvious in soils with a clay content of greater than 8% and SOC/clay of approximately 10%. The OM either influences or is inter-correlated with the processes responsible for the formation of macropores.

Freeze–thaw cycles and soil water content effects on infiltration rate of three Saskatchewan soils

Fouli, Y., Cade-Menun, B. J. and Cutforth, H. W. 2013. Freeze–thaw cycles and soil water content effects on infiltration rate of three Saskatchewan soils. Can. J. Soil Sci. 93: 485–496. Many soils at high latitudes or elevations freeze and thaw seasonally. More frequent freeze–thaw cycles (FTCs) may affect ecosystem diversity and productivity because freeze–thaw cycles cause changes in soil physical properties and affect water movement in the landscape. This study examined the effects of FTCs (0, 1, 5, and 10) and antecedent soil water content [at soil water potentials (SWP) −1.5, −0.033 and −0.02 MPa] on the infiltration rate of three Saskatchewan soils (a clay, a loam, and a loamy sand). A tension infiltrometer was used at tensions [water potentials of the tension infiltrometer (WPT)] −5, −10 and −15 cm. Infiltration rates increased with increasing SWPs for the loam and clay soils due to higher infiltrability into drier soils. Infiltration rates decreased with increasing SWPs for the loamy sand, probably the result of less surface tension, unimodal porosity, and increased gravitational potential. Infiltration rates either decreased or did not change with increasing FTCs, and this may be due to increased water viscosity as temperatures approach freezing. Also, ice may have formed in soil pores after frequent FTCs, causing lower infiltration rates. Infiltration rates for clay at −1.5 MPa were higher than for loam or loamy sand, probably the result of clay mineralogy and potential shrinking and cracking. Soil texture and initial water content had a significant effect on infiltration rates, and FTCs either maintained or lowered infiltration rates.

Temperature influences water sorptivity of soil aggregates

The aim of this study was to determine the potential development of water sorptivity of soil aggregates by heating. Soil aggregates were sampled from arable layer of 5 Polish soils: Haplic Luvisol 1 from Czesławice, Haplic Luvisol 2 from Wierzchucinek, Haplic Cambisol from Felin, Gleyic Mollic Cambisol from Chylice, and Haplic Phaeozem from Grabiec. Three aggregates of each soil type with minimum diameter between 4 and 10 mm were heated in the oven for at least 3 hours at temperatures 20, 100, 200, 250, and 360ºC. After each temperature treatment the soil aggregates were conditioned at the room temperature for 16 hours. Laboratory measurements of water sorptivity of soil aggregates were performed under a negative tension h0 = -2 cm using tension infiltrometer. It was found that the exposure to temperatures between 100 and 200°C tends to decrease water sorptivity of aggregates from all the studied soils but one (Haplic Luvisol 1), followed by about two- to four-fold increase in water sorptivity for exposure to temperatures of 250°C (in Haplic Luvisol 1, Haplic Luvisol 2, and Haplic Phaeozem) or 360°C (in Haplic Cambisol and Gleyic Mollic Cambisol).

Impact of tension infiltrometer disc size on measured soil water repellency index

Hunter, A. E., Chau, H. W. and Si, B. C. 2011. Impact of tension infiltrometer disc size on measured soil water repellency index. Can. J. Soil Sci. 91: 77–81. Accurate measurement of soil water repellency (or hydrophobicity) is important for assessing the hydraulic properties of soils. Water repellency index (RI), a measure of soil water repellency, can be determined using the tension infiltrometer. Little is known about the effects of different infiltrometer disc sizes on measured RI. Furthermore, the impact of method selection in the context of site assessment is unknown. The objective of this study was to determine if the infiltrometer disc size affects the measured RI. Studies were conducted on seven sandy and one clay site in Western Canada in 2008 and 2009. Mini (disc 4.5 cm in diameter) and standard (disc 20 cm in diameter) tension infiltrometers were used to determine RI. There was strong spatial variability in RI values at all sites. Higher RI and greater variance were associated with the smaller disc size due to the smaller zone of influence. Water repellency index values obtained from the mini and standard tension infiltrometers were not statistically different in most cases. We conclude that the mini infiltrometer is an appropriate method for site assessment of RI. The mini infiltrometer RI values were compared with those from the standard infiltrometer, resulting in a 44% accuracy rate with a type I error in 33% of the cases and a type II error in 22% of the cases.