Changes In Infiltration Rates Research Articles

Changes in water infiltration along a catena prior to mechanised clearing operations and after two cropping seasons

Maintenance of water infiltration into sloped agricultural lands is an important mechanism for both moisture supply to crops and erosion control. Changes in water infiltration of a typic Kandiudult (Rhodic Nitisols) with a 21% slope were measured in the upper-, middle- and lower-backslope segments of 9 m by 40 m run-off plots located at Makerere University Agricultural Research Institute, Kabanyolo, Uganda. Cumulative infiltration was computed for the Green-Ampt, Philips, and Kostiakov models from infiltrometer measurements taken prior to mechanised land clearing and during maize (Zea mays) cropping. Kay et al. (1994) model was used to predict the time of 50% reduction in infiltration rate. The infiltration behaviour was best described by the Kostiakov model. Changes in infiltration rate were dependent on slope position with greatest alterations recorded on the upper and middle positions. Mean cumulative infiltration after 60 minutes was highest prior to land clearing with values of 150, 97 and 97 cm for the upper-, middle- and lower-slope segments, respectively. The Kay et al. model predicted significant (P

The implications of spatial variability in surface seal hydraulic resistance for infiltration in a mound and depression microtopography

Soil surface crusting has a major impact on water infiltration and erosion in many soils. Considerable progress has been made in describing crusting processes and in modelling the impact of crusting on infiltration. Most studies, however, have neglected the high spatial variability in crust characteristics observed in the field. The objective of this experiment was to determine the influence of runoff depth on infiltration rate in the presence of a surface seal varying in hydraulic characteristics with microtopography. The Blosseville silt loam has a low aggregate stability and forms crusts readily. The Villamblain silty clay loam has a greater aggregate stability due to its greater clay and organic matter contents, and it is more resistant to aggregate breakdown processes under rainfall. Samples of the soils were sieved to retain aggregates less than 2.0 cm and packed in 50×50×15 cm soil trays. The trays were surrounded by a 10 cm soil border to compensate for splash loss. After molding the surface into a mound and depression microtopography, the samples were subjected to simulated rainfall at an intensity of 22.8 mm h −1. Hourly measurements of surface roughness showed that the original roughness was smoothed out due to the infilling of depressions by sediments detached from the mounds. For the final hour, runon was added to the top of the soil tray to increase the runoff rate and depth. For both soils, infiltration rate increased more than could be attributed to the increased ponding pressure head. The change in infiltration rate was particularly great for Villamblain. The measurements of hydraulic resistance showed that structural crusts had a lower hydraulic resistance than sedimentary crusts. They also showed that the crusts formed on Villamblain were of a lower hydraulic resistance than those of Blosseville. It appears that small changes in runoff depth can significantly increase infiltration rate when structural crusts of lower hydraulic resistance are inundated. The effect was less important in Blosseville which formed seals of relatively high hydraulic resistance everywhere. The results provide a suitable explanation for field observations of increasing infiltration rate with either increasing rainfall intensity or runoff rate. The results also have implications for the relationships between surface roughness, surface water storage, and infiltration.

The impact of sheep trampling and stocking rate on the physical properties of a red duplex soil with two initially different structures

The effect of sheep trampling and stocking rate on the physical properties of a red duplex soil with two initially different structures was examined over an 8 week period when the soil was wet following winter rains. The experimental site was located at Merredin in Western Australia where the average annual rainfall is 307 mm. A previous long-term tillage and gypsum trial at the experimental site had resulted in the development of contrasting topsoil structures. Three grazing treatments were imposed at the trial site: grazing at the normal high stocking rate (8 DSE ha-1), grazing at half the normal stocking rate (4 DSE ha-1), and no grazing (where pasture was mown to simulate grazing without trampling). Topsoil structure was assesed by measuring water-stable aggregation (> 2 mm diameter aggregates), the relative contribution of dispersion and slaking to structural instability (measured as soil strength on < 2 mm fine earth soil fractions), steady-state infiltration rates (at 10 mm tension), and in situ soil strength characteristics (measured as penetration resistance). At the end of the grazing period, all structure attributes measured showed that topsoil structure had been damaged as a result of sheep trampling. The magnitude of such structure damage was affected by the initial physical condition of the soil and stocking rate. When compared with ungrazed pasture, there was a greater decline in structural condition as a consequence of grazing on less well-structured soil than on better-structured soil. Halving the normal stocking rate reduced the degree of structure damage on both soils. Within-season variability in soil hydraulic properties was large. The temporal changes in infiltration rates were attributed to changes in drainage pore volume brought about by the growth and decay of pasture roots, the formation and disruption of a surface crust, and the processes of soil compaction and remoulding resulting from animal trampling (no direct measurements were made). The variability in hydraulic behaviour found in this study emphasizes the need to maintain consistent sampling dates and soil water contents at sampling in long-term studies on soil structure changes.

Infiltration as a tool for detecting soil changes due to cropping, tillage, and grazing livestock

AbstractSoil physical and biological properties often change when different cropping, tillage, or management systems are imposed. Changes occasionally occur quickly, but usually become evident only after months or years. Infiltration rates are affected by several soil properties and may provide the most sensitive indication of changes in soil properties. To evaluate the use of infiltration measurements for detecting changes in soil properties, we conducted infiltration tests on a cropping systems experiment, a tillage experiment, and two beef cattle grazing experiments. In Pennsylvania, significant changes in infiltration rates did not occur until more than four years after converting from a conventional to a low-input cropping system. Infiltration rates were higher on 14th-year no-till plots compared with moldboard plow and chisel treatments in an Iowa tillage study. Earthworm populations and activity were highest in the no-till treatment. Infiltration rates correlated negatively with increased stocking rates in a long-term beef grazing study in Oklahoma. The number of earthworms did not correlate positively with infiltration in this study, suggesting a complex interaction. A short-term study of overwinter beef corn-stalk grazing in Iowa did not show consistent patterns in infiltration rate or other soil properties with different stocking rates. Infiltration appears to be a good indicator of soil structural changes associated with cropping, tillage, and management systems.

Micromorphological study of surface seals developed under simulated rainfall

Soil surface seals were formed on microplots of homogeneous soil in the laboratory using simulated rainfall. The soil horizons studied varied in texture and organic matter content. The surface sealing was quantified by monitoring changes in infiltration rate, splash detachment and near-surface shear strength with time. The porosity of the resulting surface seals and unsealed soil material was studied in the laboratory using image analysis of thin sections. Various sealing indices demonstrated that the A horizons of the soil sealed to a greater extent than the corresponding Bt horizons. In general, as sealing increased, soil loss decreased from the microplots. Total porosity of the soil surface seal did not explain differences in infiltration rate, splash detachment or strength well; however, the percentage of planar pores was more related to the final infiltration rate. Different morphological types of surface seals could be found in the soils that were representative of various sealing processes. Even though some soils had a considerable amount of water-dispersible clay, the downward translocation of clay was a minor process. A more important process was the physical breakdown of aggregates and the accompanied compaction of the surface resulting in a zone with a lower percentage of planar pores. The primary particle size of the soil was a poor indicator of the soils' susceptibility to surface sealing, whereas, the water dispersible particle size, particularly the silt size distribution, was a good indicator of its sealing behavior.

Infiltration of Soils as Affected by the Pressure and Water Content at the Time of Compaction

AbstractInfiltration rates, volume reduction, and bulk densities of soils were determined on soils as a function of compacting pressures and water content at the time of compaction.Maximum compaction generally occurred when the soils were packed at water contents near field capacity.When compacting loads were < 1 kg/cm2 the minimum bulk densities occurred when soils had water contents of about one half field capacity, indicating that surface tension of water films in the soils plays a major role in cohesiveness and stabilization against compaction under these conditions.Compacting loads of 3.46 kg/cm2, at field capacity on sandy loams and finer textured soils, reduced infiltration rates to < 0.1% of values obtained after these soils had been compacted when they were air dry. In a loamy sand soil this reduction was to about 1%.The low infiltration rates following compaction were increased by wetting and drying, although several cycles of wetting and drying did not raise the infiltration rate to the level observed before packing.Freezing and thawing cycles also increased the infiltration rates of previously compacted soils. Most of the change took place in the first freezing and thawing cycle.The large changes in infiltration rates using achievable levels of compaction at the “optimum” water contents indicate that compaction can play a major role in the management of water in ditches, reservoirs, furrows, and watersheds.

Infiltration dynamics under various rangeland treatments on uniform sandy-loam soils in southeastern Utah

Studies were made, over a 3- to 8-yr. period, of mean seasonal and yearly changes in infiltration rates under various rangeland management practices within the pinyon-juniper ( Pinus spp.- Juniperus spp.) type. Results of the study indicate that mean upper limits in measured infiltration rates range from a surprising 1.37–3.47 times the mean minimal rates, each mean value representing from 6–20 replications for a given sampling date. Soil biology may be important in determining seasonal trends in infiltration rates, as well as overwintering freeze-thaw activity. Suggestions are given for sampling infiltration rates.

Use of Infiltration Equation Coefficients as an Aid in Defining Hydrologic Impacts of Range Management Schemes

Highlight: Based on infiltrometer data from 13 pinyon-juniper sites in Utah, the relationship of selected rangeland vegetation characteristics and soil physical properties to the various infiltration coeffkients contained in three well-known algebraic infiltration equations was determined. Coefftcients in Kostiakov’s equation were related more to vegetation factors than to soil &actors while coefficients in Philip’s equation were more related to soil factors than to vegetation factors. The single coefficient in Horton’s equation was somewhat intermediate, representing both vegetation and soil influences. It is conceivable that changes in rangeland use activities or intensity of use may be detected through changes encountered in infiltration coefficients, with emphasis on either vegetation or soil factors or both, depending on the equation or model used. The relationship of infiltration in native and “disturbed” rangeland plant communities to soil and vegetation parameters has been of interest to hydrologists for many years. Many devices have been designed to measure infiltration rates, and these range from ring-type infiltrometers to sprinkling-type devices that attempt to duplicate certain characteristics of natural rainfall. Based on actual measurements, various researchers have found that the results of infiltrometer trials may be expressed in terms of specific models or equations. Examples include Kostiakov’s equation (1932), Horton’s equation (1940)) and Philip’s equation (1957). Each of these equations contains various coefficients, most of which are speculatively related in some (perhaps unidentified) way to factors that may be controlling the infiltration process. The objective of this study was to determine, to the extent possible, the relationship of selected rangeland vegetation characteristics and soil physical properties to the various infiltration coefficients contained in the three well known algebraic infiltration equations mentioned above. This objective is especially pertinent in terms of possible interpretations of long- or short-term temporal changes in infiltration rates as a function of specific management plans, and especially in those circumstances where supplemental data are minimal or completely lacking. soil and vegetation

Field infiltration indices in the evaluation of tillage practices

Field infiltration rates were determined in order to evaluate different tillage treatments on a sandy loam soil. The following indices were chosen for evaluation: the infiltration rates at 5 min (IR-5), at 30 min (IR-30), and at 90 min (IR-90); the change in infiltration rate during 1 hour from 30 min to 90 min, designated as IR-(30–90); and also the cumulative infiltration at 90 min (CI-90). It was found that the index IR-(30–90) is statistically superior to other indices for the evaluation of tillage practices. It was also found that initial soil moisture content influences infiltration. The regression coefficients between initial moisture and IR-30, and initial moisture and CI-90 may also be used as indices for describing field infiltration differences. However, the index IR-(30–90) has been found to be free from the influence of initial moisture, and can be used directly for the evaluation of tillage treatments. For other soil types, however, the times used for the indices may be different.

Ridge and Furrow Liquid Waste Disposal in A Northern Latitude

The operation and performance of a municipal ridge and furrow liquid waste disposal system in use since 1959 was monitored for a year and a half. One hundred and fifty thousand gallons a day of trickling filter effluent are disposed into the soil via four 1-acre basins. A heavy stand of grass left unharvested over the winter apparently contributes to successful operation. The changes in infiltration rates and quality of the infiltrate with season and under various loading and operating conditions are examined, as are companion field and indoor lysimeter studies comparing various design and operational factors that may influence infiltration protection of ground water.

Subsurface Water Distribution in Surface Irrigation

Experimental data on subsurface water distribution show that the uniformity of water distribution is greatly dependant on the manner in which the infiltration rate changes with time after the initial wetting. The other factor of major importance in the uniformity of water distribution along runs is the time required for the wetting front to traverse the run. Equations are developed describing the subsurface water distribution in terms of three dimensionless ratios, one each for time quantities, distances along runs, and water application quantities. The subsurface water distribution uniformity is greater for soils in which the infiltration rate decreases rapidly with time than for soils in which the infiltration rate remains relatively constant, provided the other conditions during the irrigation are similar.

The Use of Undisturbed Soil Cores to Investigate the Reclamation of Saline and Alkali Soils

AbstractField leaching investigations relative to the reclamation of saline and alkali soils generally require considerable land area, as well as time and personnel, for establishing and maintaining such studies. Concurrent with a field leaching experiment a laboratory leaching study was made to determine the relationship between results obtained from undisturbed cores in the laboratory and those obtained from field plots. Changes in infiltration rate, soluble salts, and exchangeable‐sodium‐percentage due to leaching, with and without gypsum, were compared.In view of the similarity of results obtained from undisturbed cores in the laboratory and field plots, it appears that soil cores, properly encased, can be used to predict with reasonable accuracy the reclaimability of saline and alkali soils. Although laboratory studies will not replace field investigations, cores could be used in making preliminary studies during period outside of the field season. The information thus obtained could then be used in the final selection of treatments to be considered in the field.