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Soil water repellency; occurrence, consequences, and amelioration
Ritsema, C.J. ; Dekker, L.W. - \ 2003
Amsterdam : Elsevier - ISBN 0444512691 - 352
bodemwater - afstoting - bevochtigbaarheid - hygroscopiciteit - dehydratie - bodemstructuur - fysische bodemeigenschappen - hydraulisch geleidingsvermogen - soil water - repellency - wettability - hygroscopicity - dehydration - soil structure - soil physical properties - hydraulic conductivity
Influence of surfactant applications on the wettability of a dune sand with grass cover: long-term effect of Primerr604 and short-term effect of ACA 1897
Oostindie, K. ; Dekker, L.W. ; Ritsema, C.J. - \ 2003
Wageningen : Alterra (Alterra-report 659) - 54
duinzand - neerslag - infiltratie - waterafstotende gronden - oppervlaktespanningsverlagende stoffen - bodemwater - dehydratie - dune sand - precipitation - infiltration - water repellent soils - surfactants - soil water - dehydration
Occurrence of soil water repellency in arid and humid climates
Jaramillo, D.F. ; Dekker, L.W. ; Ritsema, C.J. ; Hendrickx, J.M.H. - \ 2000
Journal of Hydrology 231/232 (2000). - ISSN 0022-1694 - p. 105 - 111.
bodemwater - hydratatie - afstoting - dehydratie - evaporatie - humide klimaatzones - soil water - hydration - repellency - dehydration - evaporation - humid zones
Modeling and field evidence of finger formation and finger recurrence in a water repellent sandy soil
Ritsema, C.J. ; Dekker, L.W. ; Nieber, J.L. ; Steenhuis, T.S. - \ 1998
Water Resources Research 34 (1998)4. - ISSN 0043-1397 - p. 555 - 567.
infiltratie - hydraulisch geleidingsvermogen - kwel - bodem - hygroscopiciteit - hydratatie - dehydratie - modellen - onderzoek - infiltration - hydraulic conductivity - seepage - soil - hygroscopicity - hydration - dehydration - models - research
Stable or unstable wetting fronts in water repellent soils - effect of antecedent soil moisture content
Ritsema, C.J. ; Nieber, J.L. ; Dekker, L.W. ; Steenhuis, T.S. - \ 1998
Soil & Tillage Research 47 (1998). - ISSN 0167-1987 - p. 111 - 123.
infiltratie - hydraulisch geleidingsvermogen - kwel - bodem - hygroscopiciteit - hydratatie - dehydratie - infiltration - hydraulic conductivity - seepage - soil - hygroscopicity - hydration - dehydration
Biologisch afbreekbare smeermiddelen
Straelen, B.C.P.M. van - \ 1998
Tuin en Park Techniek 5 (1998)2. - ISSN 1380-3212 - p. 34 - 35.
roadsides - weed control - hot air treatment - heat treatment - plant protection - control methods - temperature - hydration - dehydration - wegbermen - onkruidbestrijding - heteluchtbehandeling - warmtebehandeling - gewasbescherming - bestrijdingsmethoden - temperatuur - hydratatie - dehydratie
Bijzonderheden over een nieuwe thermische onkruidbestrijder die werkt met stoom van een temperatuur tussen de 120 en 140 graden Celsius
Flow and transport in water repellent sandy soils
Ritsema, C.J. - \ 1998
Agricultural University. Promotor(en): R.A. Feddes; J. Bouma. - S.l. : S.n. - ISBN 9789054859154 - 215
infiltratie - hydraulisch geleidingsvermogen - kwel - bodem - hygroscopiciteit - hydratatie - dehydratie - zandgronden - infiltration - hydraulic conductivity - seepage - soil - hygroscopicity - hydration - dehydration - sandy soils

Water repellency in soils is currently receiving increasing attention from scientists and policy makers, due to the adverse and sometimes devastating effects of soil water repellency on environmental quality and agricultural crop production. Soil water repellency often leads to severe erosion and runoff, rapid leaching of surface-applied agrichemicals, and loss of water and nutrient availability for crops.

In general, soils become water repellent through the coating of soil particles or structural elements with water repellent organic substances originating from decaying plant material. Soil water repellency manifests itself when the water content of the soil drops below a critical level. Water flow and solute transport patterns are complex under such conditions. The present study deals with flow and transport processes in an untilled, grass-covered water repellent sandy soil consisting of three layers.

Extensive tracer experiments indicate that distribution flow dominates in the humous top layer, preferential flow in the water repellent sand layer, and diverging flow in the underlying wettable zone. Preferential flow paths or fingers occur almost throughout the year. Fingers develop rapidly during severe rain storms, causing significant portions of the infiltrating water to be preferentially transported to the deep subsoil. Fingers form at sites with relatively low degrees of water repellency, and finger diameters range from 10 to 25 cm.

Model simulations show that fingered flow results from hysteresis in the water retention function, and the nature of the formation depends on the shape of the main wetting and drainage branches of that function. Once fingers are established, hysteresis causes them to recur along the same pathways during subsequent rain events. In the long term, recurrence of fingers may lead to changes in physical and/or chemical properties of the soil within the fingered flow pathways. It is only under initially dry conditions, with soil water contents below the critical level, that fingers will be formed during infiltration. Under wetter conditions, with soil water contents above the critical level, wetting fronts will remain stable and no fingers will develop.

Future research should focus on improving our understanding of the origins, occurrence, hydrological responses and agricultural functioning of water repellent soils.

Moisture variability resulting from water repellency in Dutch soils
Dekker, L.W. - \ 1998
Agricultural University. Promotor(en): J. Bouma; R.A. Feddes. - S.l. : Dekker - 240
bodemwater - bodem - hygroscopiciteit - hydratatie - dehydratie - geostatistiek - soil water - soil - hygroscopicity - hydration - dehydration - geostatistics

The present study suggests that many soils in the Netherlands, in natural as well as in agricultural areas, may be water repellent to some degree, challenging the common perception that soil water repellency is only an interesting aberration. When dry, water repellent soils resist or retard water infiltration into the soil matrix. Soil water repellency can lead to the development of unstable wetting and preferential flow paths. Preferential flow has wide-ranging significance for rapid transport of solutes, such as agrichemicals, towards the groundwater and surface water, making it essential to understand this phenomenon.

The persistence and degree of water repellency was examined in topsoils of nature reserves and cultivated soils, using the water drop penetration time (WDPT) and alcohol percentage tests. The severity of water repellency measured on dried soil samples, the so-called "potential" water repellency, can be used as a parameter for comparing soils with respect to their sensitivity to water repellency. In some cases, however, the severity of potential water repellency was found to be sensitive to the initial moisture content of the soil and the temperature during drying. Measurement of the "actual" water repellency on field-moist samples determines the soil fraction excluded from direct solute and water flow. However, preferential flow is a dynamic process, which is why the ratio between water repellent and wettable soil is time dependent. The "critical soil water content", below which the soil in the field is water repellent and above which the soil is wettable, was found to be a useful parameter in water repellency studies.

Spatial and temporal variability in volumetric soil water content was studied in vertical transects by intensive sampling with 100 cm 3steel cylinders. Spatial variability in soil water content under grass cover was high, due to fingered flow. On arable land, vegetation and microtopography appeared to play a dominant role. This thesis provides examples of uneven moisture patterns in water repellent sand, loam, clay and peat soils with grass cover, and in cropped, water repellent sandy soils.

Recurring fingered flow pathways in a water repellent sandy field soil
Ritsema, C.J. ; Dekker, L.W. ; Elsen, E.G.M. van den; Oostindie, K. ; Steenhuis, T.S. ; Nieber, J.L. - \ 1997
Hydrology and Earth System Sciences 1 (1997)4. - ISSN 1027-5606 - p. 777 - 786.
bodem - hygroscopiciteit - hydratatie - dehydratie - zandgronden - soil - hygroscopicity - hydration - dehydration - sandy soils
Three-dimensional fingered flow patterns in a water repellent sandy field soil
Ritsema, C.J. ; Dekker, L.W. ; Heijs, A.W.J. - \ 1997
Soil Science 162 (1997)2. - ISSN 0038-075X - p. 79 - 90.
dehydratie - hydratatie - hydraulisch geleidingsvermogen - hygroscopiciteit - infiltratie - zandgronden - kwel - bodem - dehydration - hydration - hydraulic conductivity - hygroscopicity - infiltration - sandy soils - seepage - soil
Water flow and transport through the vadose zone of water-repellent field soils take place mainly through preferred flow paths. For modelling purposes, it is essential to know when fingers can be expected and what their average dimension is. Thereforeten soil blocks, each 1.2 m long, 0.6 m wide and 0.52 m deep, were sampled in a water-repellent sandy field soil. Fingered flow patterns were distinct in soil blocks sampled after rain events. Fingers were found where the degree of potential water repellency in the upper part of the soil was low.
Preferente stroming en vochtpatronen in waterafstotende zavel-, klei- en veengronden
Dekker, L.W. ; Ritsema, C.J. - \ 1996
Stromingen : vakblad voor hydrologen 2 (1996)4. - ISSN 1382-6069 - p. 23 - 35.
hoogveengronden - dehydratie - hydratatie - hydraulisch geleidingsvermogen - hygroscopiciteit - infiltratie - veengronden - kwel - bodem - moerasgronden - bog soils - dehydration - hydration - hydraulic conductivity - hygroscopicity - infiltration - peat soils - seepage - soil - swamp soils
Meststoffen en andere chemicaliën komen vaak sneller in het grondwater terecht dan modellen voorspellen. De meeste modellen zijn namelijk gebaseerd op de veronderstelling dat de bodem homogeen is, het water in de onverzadigde zone verticaal infiltreert en het vochtfront evenwijdig is aan het bodemoppervlak. In werkelijkheid stroomt het water vaak via preferente banen door de bodem. Preferente stroming heeft diverse oorzaken en kan in nagenoeg alle gronden optreden. In dit artikel wordt naar voren gebracht dat regenwater zich in zavel-, klei- en veengronden niet alleen snel naar de ondergrond verplaatst door scheuren en gangen, maar dat tevens de bovengrond ongelijkmatig bevochtigd wordt, waardoor vochtpatronen in de matrix van deze gronden ontstaan
Variation in water content and wetting patterns in Dutch water repellent peaty clay and clayey peat soils
Dekker, L.W. ; Ritsema, C.J. - \ 1996
Catena 28 (1996)1-2. - ISSN 0341-8162 - p. 89 - 105.
hoogveengronden - dehydratie - hydratatie - hygroscopiciteit - nederland - veengronden - bodem - moerasgronden - bog soils - dehydration - hydration - hygroscopicity - netherlands - peat soils - soil - swamp soils
The variation in water content of grass-covered peaty clay and clayey peat soils was studied at six sites in the Netherlands. The topsoils were water-repellent during dry spells. When the topsoils were dry, they could absorb water only with difficultywhich is illustrated by wetting rate measurements. Precipitation could flow rapidly through shrinkage cracks towards the subsoil, bypassing the matrix of the peat. The measurements, however, revealed that preferential flow was not limited to macropore flow: irregular, finger-like wetting patterns were also formed in the soil matrix. Owing to these typical wetting patterns, soil water content varied over short distances at all the sites on all the sampling dates.
Uneven moisture patterns in water repellent soils
Dekker, L.W. ; Ritsema, C.J. - \ 1996
Geoderma 70 (1996)2/4. - ISSN 0016-7061 - p. 87 - 99.
dehydratie - hydratatie - hydraulisch geleidingsvermogen - hygroscopiciteit - infiltratie - kwel - bodem - dehydration - hydration - hydraulic conductivity - hygroscopicity - infiltration - seepage - soil
In the Netherlands, water-repellent soils are widespread and they often show irregular moisture patterns, which cause accelerated transport of water and solutes to the groundwater and surface water. Under grass cover, spatial variability in soil moisture content is high owing to fingered flow; in arable land, vegetation and microtopography play a dominant role. Examples are given of uneven soil moisture patterns in water-repellent sandy, loam, clay and peat soils with grass cover, and in cropped water-repellent sandy soils. In addition, the influence of fungi on inducing soil moisture patterns is illustrated as well.
Preferential flow paths in a water repellent clay soil with grass cover
Dekker, L.W. ; Ritsema, C.J. - \ 1996
Water Resources Research 32 (1996)5. - ISSN 0043-1397 - p. 1239 - 1249.
zware kleigronden - dehydratie - graslanden - hydratatie - hydraulisch geleidingsvermogen - hygroscopiciteit - infiltratie - kwel - bodem - clay soils - dehydration - grasslands - hydration - hydraulic conductivity - hygroscopicity - infiltration - seepage - soil
Grass-covered heavy basin clay soils in the Netherlands appeared to be water-repellent. Water-repellency in the top layers of these soils occurred mainly as a coating on the aggregates. Differences between minimum and maximum soil moisture contents were high in all the layers sampled. When the clay soil is dry, a major proportion of the water from precipitation or sprinkler irrigation may flow rapidly through shrinkage cracks to the subsoil, bypassing the matrix of the clay peds. However, preferential flow is not limited to macropore flow; irregular wetting patterns are also formed through the small pores of the matrix.
Predicted and observed finger diameters in field soils
Ritsema, C.J. ; Steenhuis, T.S. ; Parlange, J.Y. ; Dekker, L.W. - \ 1996
Geoderma 70 (1996)2/4. - ISSN 0016-7061 - p. 185 - 196.
dehydratie - hydratatie - hydraulisch geleidingsvermogen - hygroscopiciteit - infiltratie - kwel - bodem - dehydration - hydration - hydraulic conductivity - hygroscopicity - infiltration - seepage - soil
Wetting front instability resulting in fingered flow has been found in both wettable and non-wettable soils. Laboratory research has resulted in a number of expressions for finger diameter. The applicability of one of these equations was tested for three soils where detailed soil moisture contents were measured. Information needed for finger prediction, such as the main wetting and drying loops of the soil moisture characteristic curves, were measured as well. Predicted finger diameters for the two sandy soils agreed well with the observed moisture patterns, whereas for the loess soil the wetting front was flat as predicted. The finger diameters in dry soil were based on the main wetting loop and in the wet soils they were dependent on the main drying loop.
Transport of water and solutes in wettable and water repellent sandy soils
Ritsema, C.J. ; Dekker, L.W. - \ 1996
In: Soil structure and transport processes : implications for water, gases, nutrients, pesticides, and contaminants in soils / Raats, P.A.C., Rogaar, H., van den Heuvel-Pieper, A.H., - p. 95 - 108.
dehydratie - hydratatie - hydraulisch geleidingsvermogen - hygroscopiciteit - infiltratie - zandgronden - kwel - bodem - dehydration - hydration - hydraulic conductivity - hygroscopicity - infiltration - sandy soils - seepage - soil
The research yielded the following conclusions and results: preferential flow can be expected in recently deposited, loosely packed, wettable dune sands; preferential flow is common in most water-repellent sandy soils; distribution flow in topsoils isa process of major importance, resulting in a spatially heterogeneous distribution of water and solutes in soils; with the potential water repellency parameter soils can be compared with respect to their sensitivity to water repellency; a two-dimensionalwater flow model, including hysteresis, has been developed, which is able to simulate finger growth and persistence.
Water repellency and its role in forming preferred flow paths in soils
Ritsema, C.J. ; Dekker, L.W. - \ 1996
Australian Journal of Soil Research 34 (1996). - ISSN 0004-9573 - p. 475 - 487.
dehydratie - hydratatie - hydraulisch geleidingsvermogen - hygroscopiciteit - infiltratie - kwel - bodem - dehydration - hydration - hydraulic conductivity - hygroscopicity - infiltration - seepage - soil
The role of water-repellency in forming preferred flow paths and in accelerating solute transport is explained on the basis of extensive field measurements in a grass-covered water-repellent sandy soil in the Netherlands. When the 9 cm thick humous topsoil was wetted to 20-25 vol.%, preferred flow paths, or fingers, were formed in the sandy subosil. The fingers started at the layer interface at `weak' spots with a relatively low degree of potential water-repellency, and protruded vertically into the sandy subsoil. The fingers disappeared during dry periods and recurred at the same locations during new rain events.
Influence of sampling strategy on detecting preferential flow paths in water-repellent sand
Ritsema, C.J. ; Dekker, L.W. - \ 1996
Journal of Hydrology 177 (1996)1-2. - ISSN 0022-1694 - p. 33 - 45.
dehydratie - hydratatie - hygroscopiciteit - bemonsteren - bodem - grondanalyse - dehydration - hydration - hygroscopicity - sampling - soil - soil analysis
A sample spacing up to 22 cm over a distance of several metres is just sufficient to collect information about preferential flow paths in a water-repellent sandy soil. When larger sample spacings were used, the water content distributions became more horizontally stratified. Increasing the sample size by pooling pairs of adjacently taken 100 cm3 soil samples over a distance of several metres still allowed preferential flow paths to be detected. Preferential flow paths were no longer observed for larger sample sizes. Enlarging the sample size reduces the calculated standard deviation and coefficient of variation. Sampling strategies must be flexible in design.
Solute leaching in a sandy soil with a water-repellent surface layer: a simulation.
Rooij, G.H. de; Vries, P. de - \ 1996
Geoderma 70 (1996)2-4. - ISSN 0016-7061 - p. 253 - 263.
bodem - hygroscopiciteit - hydratatie - dehydratie - infiltratie - hydraulisch geleidingsvermogen - kwel - soil - hygroscopicity - hydration - dehydration - infiltration - hydraulic conductivity - seepage
Many sandy soils in the Netherlands have a water-repellent surface layer covering a wettable soil with a shallow groundwater table. Fingers form in the water-repellent surface layer and rapidly transport water and solutes to the wettable soil in which the streamlines diverge. Although several field observations are available, this system has not yet been studied systematically. In this paper, we present a model with a steady-state water flow to which solutes are added as a pulse. The model predicts the flow through the distribution zone and through the finger in the water-repellent surface layer with a closed form solution and transport in the wettable subsoil numerically. Model calculations show that the travel time through the water-repellent surface layer and the thickness and hydraulic conductivity of the wettable soil have the strongest effect on the arrival time of the solute pulse at groundwater level. The calculations also show that, assuming transport in the wettable subsoil to take place in fingers, the travel time is considerably shorter than when the diverging flow in the wettable soil is included.
Preferential flow in water-repellent sandy soils : model development and lysimeter experiments
Rooij, G.H. de - \ 1996
Agricultural University. Promotor(en): R.A. Feddes. - S.l. : De Rooij - ISBN 9789054855385 - 229
bodem - hygroscopiciteit - hydratatie - dehydratie - zandgronden - infiltratie - hydraulisch geleidingsvermogen - kwel - modellen - onderzoek - soil - hygroscopicity - hydration - dehydration - sandy soils - infiltration - hydraulic conductivity - seepage - models - research - cum laude

When water enters a water-repellent topsoil, preferential flow paths develop and the flow bypasses a large part of the unsaturated zone. Therefore, preferential flow caused by water- repellency is expected to accelerate solute leaching to the groundwater. In soils with water-repellent toplayers and groundwater-affected wettable sublayers, a flow pattern develops that consists of three regions. In the top few centimeters, water flow converges toward the tops of the preferential flow paths. Within the preferential flow paths, water moves vertically downward. In the wettable subsoil, the flow diverges due to matric: forces. A new analytical three-region model is developed to calculate convective transport of an inert tracer in this steady-state flow system. Calculations with this model show that the wettable subsoil largely determines the residence time in the unsaturated zone and the shape of the breakthrough curve. For a sandy soil with a wettable soil of 1.20 m thickness on average, model results indicate that spreading of the solute front on the field scale caused by soil heterogeneity can be much larger than the front spreading caused by the diverging flow in the wettable subsoil.

A new type of lysimeter was built to study the spatial distribution of drainage and solute leaching with a resolution of 5 cm from an undisturbed sandy soil column with a water-repellent toplayer (1.00 m 2area, 0.55 m height). The experiments provided strong support for the concepts underlying the preferential flow model. Additionally, during an eight-month period of uninterrupted experimentation, unique observations of the long-term dynamics of unsaturated flow were made. Areas of high drainage moved over lateral distances of up to 0.25 m, and the distribution of drainage over different areas with large drainage amounts varied slowly but strongly. The three-region analytical model can reproduce without calibration the breakthrough of a chloride pulse reasonably well. In combination with the support provided by the lysimeter data for the underlying concepts, this makes the model a promising starting point for a transient, numerical model for solute transport in fields with water-repellent toplayers.

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