Testing Soil Encasing Materials for Measuring Hydraulic Conductivity of a Sandy-Loam Soil by the Cube Methods

The Cube Method (CM) and the Modified Cube Method (MCM) were developed for measuring vertical (K v ) and horizontal (K h ) saturated hydraulic conductivity of a single soil sample. By these methods, a cube of soil is carved out in situ and a suitable material is applied to enclose the cube in a tightly fitting casing before moving the sample to the laboratory. Problems may be associated with the use of gypsum, originally used to encase soil. The suitability of molten wax and expandable polyurethane foam to encase a soil cube was tested for a sandy-loam soil. Wax-treated samples yielded lower conductivity results than untreated samples by a maximum factor of 3.7. The observed discrepancies w…

Fitting particle size distribution models to data from Burundian soils for the BEST procedure and other purposes

Testing the Beerkan Estimation of Soil Transfer (BEST) soil particle size distribution (PSD) model is necessary to evaluate the applicability of the BEST procedure for characterising soil hydraulics. In this investigation, the fitting performance of the BEST PSD model was tested using a database of 114 Burundian soils with 14 measured particle size fractions for each soil sample, and also by considering a reduced number of measured particle size fractions for a sample. The fitting performance of the model developed by Fredlund et al. (2000) (FR model) was also considered for comparative purposes. On average, the BEST model yielded satisfactory results (i.e., mean relative error, E r ¯ = 3.9…

Determinazione delle proprietà idrauliche del suolo in una pendice naturale

Approfondimenti su alcune tecniche infiltrometriche per la misura delle conducibilità idraulica del suolo saturo

Nella memoria vengono approfonditi alcuni aspetti della misura in campo della conducibilità idraulica del suolo saturo, Kfs, con tecniche infiltrometriche. In primo luogo, è stata determinata la frequenza degli insuccessi con una prova del tipo Two- Ponding-Depth effettuata con l’infiltrometro ad anello singolo (PI). La suddetta frequenza è risultata più elevata in due suoli franco-argillosi (40%) che in uno franco-sabbioso (25%). Un contenuto idrico iniziale elevato ha costituito una possibile causa di fallimento della misura. L’esclusione dal data set delle prove che hanno fornito valori del parametro * ricadenti al di fuori del range 1-100 m-1 è risultata ininfluente solo nel caso in cu…

Using the simplified falling head technique to detect temporal changes in field-saturated hydraulic conductivity at the surface of a sandy loam soil

Abstract Determining temporal changes in field-saturated hydraulic conductivity ( K fs ) is important for understanding and modeling hydrological phenomena at the field scale. Little is known about temporal variability of K fs values measured at permanent sampling points. In this investigation, the simplified falling head (SFH) technique was used for an approximately 2-year period to determine temporal changes in K fs at 11 permanent sampling points established at the surface of a sandy loam soil. Additional K fs measurements were obtained by the single-ring pressure infiltrometer (PI) technique to also compare the SFH and PI techniques. The lowest mean values of K fs , M ( K fs ), were det…

Using a transient infiltrometric technique for intensively sampling field-saturated hydraulic conductivity of a clay soil in two runoff plots

The point measurement of soil properties allows to explain and simulate plot scale hydrological processes. An intensive sampling was carried out at the surface of an unsaturated clay soil to measure, on two adjacent plots of 4 × 11 m2 and two different dates (May 2007 and February–March 2008), dry soil bulk density, ρb, and antecedent soil water content, θi, at 88 points. Field-saturated soil hydraulic conductivity, Kfs, was also measured at 176 points by the transient Simplified Falling Head technique to determine the soil water permeability characteristics at the beginning of a possible rainfall event yielding measurable runoff. The ρb values did not differ significantly between the two d…

Misura della conducibilità idraulica del suolo con l’infiltrometro a depressione a dischi concentrici

Testing laboratory methods to determine the anisotropy of saturated hydraulic conductivity in a sandy–loam soil

Abstract Anisotropy, a (the log of the ratio of horizontal to vertical conductivity, log 10 ( K h / K v )), of saturated soil hydraulic conductivity, K s , affects transport processes in soil but is not routinely measured, probably because practical and validated methods are lacking. The objective of this investigation was to determine the effects of different constant-head laboratory and sampling procedures on anisotropy of saturated hydraulic conductivity measurements. The sequence of K s measurements was varied (vertical conductivity, K v , first, then horizontal, K h , second and vice versa) for an experimental set-up considering five variables: 1) water ponding type (Mariotte or siphon…

Testing different approaches to characterize Burundian soils by the best procedure

Abstract The Beerkan Estimation of Soil Transfer parameters (BEST) procedure seems attractive for soil hydraulic characterization but it has received little testing so far. The objective of this investigation was to test BEST with different application approaches for some soils in Burundi, where there is the need of using simple methods to characterize soils. Most (14) of the 19 sampled sites had a clay soil texture whereas texture ranged from silty clay to loam in the other cases. On average, the fitting ability of both the particle size distribution (PSD) model (mean relative error, Me ( E r ) = 2.0%) and the cumulative infiltration model ( Me ( E r ) = 2.3%) was good according to recomme…

Using the single-ring infiltrometer method to detect temporal changes in surface soil field-saturated hydraulic conductivity

Abstract Determining temporal changes in field-saturated hydraulic conductivity ( K fs ) is important for understanding and modelling hydrological phenomena at the field scale. Little is known about the sensitivity of temporal change estimates to the method used for measuring K fs . The objective of this study was to compare temporal changes in K fs obtained in the surface layer of a clayey soil using two application procedures of the single-ring infiltrometer method. Rings installed permanently at the beginning of a 1.5-year study period (permanent sites, PSs, sample size N =16) and rings installed immediately before conducting the infiltrometer measurement (non-permanent sites, NPSs, N =1…

Funzioni di pedotrasferimento per la determinazione della curva di ritenzione idrica dei suoli siciliani

Il ricorso alle funzioni di pedotrasferimento (PTF) rende possibile una stima relativamente agevole delle caratteristiche di ritenzione idrica del suolo. Una riproduzione accurata delle misure per un’area di interesse presuppone però l’accertamento delle prestazioni delle PTF esistenti ed, eventualmente, lo sviluppo di PTF alternative. Utilizzando 217 curve di ritenzione misurate in Sicilia, nell’indagine è stata dapprima verificata l’applicabilità di alcune delle più diffuse PTF disponibili in letteratura. Tale verifica ha evidenziato che i risultati migliori competono alle PTF che includono, tra le variabili indipendenti, la densità apparente del suolo. Poiché tale proprietà fisica non se…

Effect of laboratory procedures on the integrity of a sandy-loam soil sample for bi-directional measurement of saturated hydraulic conductivity

Practical and validated methods to measure anisotropy of saturated, Ks, or field-saturated, Kfs, soil hydraulic conductivity on a single soil sample are still lacking. The objective of this investigation was to test factors affecting anisotropy measured in a sandy-loam soil by the constant-head laboratory permeameter and the modified cube method. The ratio, RK, between the conductivity results obtained with a long (6 h) and a short (0.5 h) duration run varied from a minimum of 0.29 to a maximum of 0.88 with the considered experimental procedure, differing by both the employed constant-head device (Mariotte bottle, siphon) and the initial soil water content (unsaturated, saturated). Maximum …

Predicting the water retention characteristic of Sicilian soils by pedotransfer functions.

Indagine sulla qualità fisica di alcuni suoli siciliani

La valutazione della qualità fisica del suolo rappresenta un aspetto di notevole importanza negli studi agronomici e ambientali. Nell’indagine è stato approfondito il tema dell’applicabilità in Sicilia dell’indice di qualità fisica del suolo S, basato sulla misura della curva di ritenzione idrica. Il suddetto indice assume valori crescenti nel passaggio da un suolo di qualità scadente ad uno di buona qualità. Conformemente alle attese, i valori di S, determinati per 199 campioni di suolo, si sono ridotti all’aumentare del contenuto di argilla e di limo, della densità apparente e del fattore di erodibilità del suolo. Inoltre, l’acqua disponibile e la capacità di aerazione sono aumentate mono…

Approfondimenti sul Cube Method per la misura della conducibilità idraulica del suolo

Soil physical quality in a Sicilian agricultural area

Comparing two methods of analysis of single-ring infiltrometer data for a sandy – loam soil

The single-ring pressure i n filtrometer (PI) with the steady-state Two-Ponding-Depth (TPD) applic ation method were developed to simulta neously determine the saturated soil hydraulic conductivity, K , and the α ⁎ -parameter in the fi eld. Methods of analysis of transient PI data are also available but they have received little testing so far. The transient WU method and the TPD method were compared for a sandy-loam soil. A linearization technique o f the in filtration curve yielded more reliable K fs fs and α ⁎ results (i.e., falling within expected ranges) than a non-linear optimization technique. The WU method gave both positive and reasonable K and α ⁎ values for all infi ltration tests. U…

Testing the concentric-disk tension infiltrometer for field measurement of soil hydraulic conductivity

Abstract The concentric-disk tension infiltrometer (CDTI) may be used to simultaneously measure the confined ( K c ) and the unconfined ( K u ) soil hydraulic conductivity, but it has received little testing. Comparison between K c and K u can be affected by the calculation approach applied to analyze unconfined steady-state infiltration rates. The objectives of this investigation were to: i) establish the effect of the calculation approach on the estimates of K u ; and ii) compare the K c and K u values measured by the CDTI. A clay soil, a structureless sandy loam soil, and a sandy loam soil with a relatively high gravel content were sampled using a disk of radius equal to 107.5 mm, compri…

Physical and hydraulic characterization of a clay soil at the plot scale

Summary The soil physical and hydraulic properties have to be determined for interpreting and simulating many hydrological processes. An investigation was carried out to determine the physical and hydraulic characteristics of a clay soil at the plot scale. An intensive sampling of the surface soil layer of two plots of 4 × 11 m2 was carried out by measuring, for each plot, dry soil bulk density, ρb, and antecedent soil water content, θi, at 88 sampling points and field-saturated soil hydraulic conductivity, Kfs, at 176 sampling points. A wide range of Kfs values (0.7–5107 mm h−1) were measured by the Simplified Falling Head (SFH) technique. For each variable, the two plots yielded very simi…

A laboratory analysis of falling head infiltration procedures for estimating the hydraulic conductivity of soils

Abstract Falling head (FH) infiltration procedures can give rapid estimates of the field saturated hydraulic conductivity ( K fs ) of soils. The objectives of this investigation were to develop a procedure for estimating both the K fs and the α ⁎ parameter of the exponential hydraulic conductivity function from a FH experiment, and to compare FH procedures differing by experimental and computational demands. A total of 33 FH experiments were carried out on repacked, sandy loam and loam soil cores. A two level (TL) analysis was applied to determine a value of α ⁎ for each soil core. K fs was then calculated by three different approaches, ranging from the fitting approach (FA) that used the m…

Comparing two methods of analysis of single-ring infiltrometer data for a sandy–loam soil

Abstract The single-ring pressure infiltrometer (PI) with the steady-state Two-Ponding-Depth (TPD) application method were developed to simultaneously determine the saturated soil hydraulic conductivity, K fs , and the α ⁎-parameter in the field. Methods of analysis of transient PI data are also available but they have received little testing so far. The transient WU method and the TPD method were compared for a sandy-loam soil. A linearization technique of the infiltration curve yielded more reliable K fs and α ⁎ results (i.e., falling within expected ranges) than a non-linear optimization technique. The WU method gave both positive and reasonable K fs and α ⁎ values for all infiltration t…

USING A TRANSIENT INFILTROMETRIC TECHNIQUE FOR INTENSIVELY SAMPLING FIELD-SATURATED HYDRAULIC CONDUCTIVITY OF A CLAY SOIL IN TWO RUNOFF PLOTS

Point measurement of soil properties allows to explain and simulate plot scale hydrological processes. An intensive sampling was carried out at the surface of an unsaturated clay soil to measure, on two adjacent plots of 4×11 m2 and two different dates (May 2007 and February-March 2008), dry soil bulk density, rb, and antecedent soil water content, qi, at 88 points. Field-saturated soil hydraulic conductivity, Kfs, was also measured at 176 points by the transient Simplified Falling Head technique to determine the soil water permeability characteristics at the beginning of a possible rainfall event yielding measurable runoff. The rb values did not differ significantly between the two dates b…

Effetto della dimensione dell'anello sulla conducibilità idraulica del suolo saturo misurata con la tecnica SFH

Nel lavoro è stata esaminata la relazione tra la conducibilità idraulica del suolo saturo, Kfs, misurata in campo con la tecnica Simplified Falling Head (SFH) e la dimensione della superficie campionata con una singola prova. L’indagine è stata condotta in un suolo franco-sabbioso ed in uno franco-limoso, esplorando la medesima superficie complessiva (0.71 m2) con anelli di diametro compreso tra 0.15 e 0.30 m. Nel suolo franco-sabbioso, le misure di Kfs effettuate con gli anelli piccoli sono risultate significativamente più elevate di quelle ricavate con gli anelli grandi. In particolare, i valori medi hanno mostrato una discrepanza di un fattore 1.7 e il ricorso agli anelli piccoli ha dete…

Misura della conducibilità idraulica del suolo saturo con i metodi del cubo

Comparison of 1D and 3D hydraulic conductivity measured by the concentric-disk tension infiltrometer.