bluuebunny/crossref_metadata_2025_split huggingface dataset:
The kinetics and energetics of transitions between water repellent and wettable soil conditions: a linear free energy analysis of the relationship between WDPT and MED/CST
Authors: Douglas Peter , Mainwaring Kathryn A. , Morley Christopher P. , Doerr Stefan H. 
Published: July 2007

AbstractSoil water repellency is commonly assessed using the Water Droplet Penetration Time (WDPT) and Molarity of Ethanol (MED) or Critical Surface Tension (CST) tests. The former is a kinetic measurement indicating the persistence of water repellency; the latter, a thermodynamic measurement, gives the initial severity of water repellency. This study aims to provide a theoretical framework to understand (i) what determines differences in persistence and initial severity of soil water repellency and (ii) correlations between such data. A linear free energy relationship between Solution Droplet Penetration Time (SDPT) and the difference between the surface tension of the droplet solution, γsol, and the Critical Surface Tension of the soil, γcx, has been derived.

Here: γsol is the surface tension of water (for WDPT) or the solution being used (SDPT); N is the number of adsorbed molecules per unit area; k the Boltzmann constant; T the temperature; A is 1/SDPT when γcx = γsol; and f is an experimentally determined parameter. WDPT, SDPT (ethanol/water and propan‐1‐ol/water), and CST measurements for a group of sandy soils support this analysis. The value of f obtained (4·2 ( ± 0·4)), suggests that the surface free energy contribution to the free energy of activation of wetting is given by the difference between the cohesive energy of the molecular film adsorbed on the soil grains and that of the wetting solution.In this interpretation: γcx is determined by the cohesive energy of the organic film adsorbed on the soil; WDPT is determined by the difference in cohesive energies between this adsorbed film and the droplet solution; and soil‐to‐soil variations in both WDPT and γcx are due to organic films of different cohesive energies present on the soil particles. For aqueous solutions of simple linear alcohols and ketones, SDPT depends on γsol but is independent of the compound used to control γsol. Copyright © 2007 John Wiley & Sons, Ltd.
Infiltration into effluent irrigation‐induced repellent soils and the dependence of repellency on ambient relative humidity
Authors: Wallach R. , Graber E. R. 
Published: July 2007

AbstractAs a result of water scarcity and as a means of wastewater disposal, reuse of treated sewage effluent in irrigated agriculture is practiced worldwide. Among the detrimental aspects of wastewater re‐use in agriculture is the possibility that soils will be rendered water repellent. The current study focuses on time dependent variation of infiltration rate in effluent‐induced repellent soils, and time dependent variation in water repellency at different levels of ambient relative humidity (RH).The shape of the cumulative infiltration curve of water was found to depend on the repellency degree (concave for wettable and slightly repellent soils, convex for severely repellent soil). Compared with infiltration rates in the wettable and slightly repellent soils, infiltration rates in the severely repellent soil were very low at the beginning and then increased. When the liquid‐vapor surface tension was reduced by means of ethanol addition to the infiltrating solution, the cumulative infiltration curve of the severely repellent soil also became concave.Repellency degree (as measured by WDPT) was found to be essentially constant over a large range of ambient RH values (<10 − ∼81%), and to increase sharply at values above 90%. The relative increase in water drop penetration time (WDPT) at high RH was greatest for the least repellent soil (10‐fold increase in WDPT), and least for the most repellent soil (2‐fold increase in WDPT). At RH > 90%, the time to reach equilibrium with respect to WDPT and soil moisture content was similar. In contrast, at values of ambient RH ranging from < 10 to 81%, WDPT was invariant over the course of reaching equilibrium with respect to moisture content. However, after reaching moisture content equilibrium, WDPT declined with increasing time. Copyright © 2007 John Wiley & Sons, Ltd.
Surface runoff as affected by soil water repellency in a Japanese cypress forest
Authors: Miyata Shusuke , Kosugi Ken'ichirou , Gomi Takashi , Onda Yuichi , Mizuyama Takahisa 
Published: July 2007

AbstractRecent studies have suggested that soil water repellency can be one of the important factors affecting hydrological processes on headwater catchments. In Japan, water repellency is known to occur under Japanese cypress (Chamaecyparis obtusa) forests, a typical plantation type in Japan, however, previous studies have not evaluated the severity of water repellency and its effects on surface runoff generation. To quantify water repellency and its effects, this study combined the critical surface tension (CST) test with a new spraying experiment in which the infiltration rates of water and ethanol solutions sprayed over 0·09‐m2 plots were compared. Long‐term intensive hydrological observations of surface runoff from 2‐m2 plots, soil water potential, and soil water content were conducted concurrently.The spraying experiment revealed that strong water repellency in surface soils, as quantified by the CST test, caused Hortonian overland flow despite the high conductivity measured under saturated hydrophilic conditions. Generally, the surface runoff coefficient for a storm event was negatively correlated with initial soil moisture conditions. However, during a period of successive storm events separated by short intervals, the coefficient decreased gradually even when the initial moisture conditions were similar, indicating a weakening of water repellency by repeated wetting. On the other hand, a drying period with long inter‐rainfall intervals and increasing air temperature was associated with increases in the surface runoff coefficient. These results suggest that the water repellency and the resultant surface runoff depended on the history of rainfall at the site. Relationships between soil water potential and soil water content indicate that changes in the soil water repellency and consequently surface runoff coefficient could occur during a single storm event. Copyright © 2007 John Wiley & Sons, Ltd.
Water repellency under different plant species in a calcareous forest soil in a semiarid Mediterranean environment
Authors: Mataix‐Solera J. , Arcenegui V. , Guerrero C. , Mayoral A. M. , Morales J. , González J. , García‐Orenes F. , Gómez I. 
Published: July 2007

AbstractWater repellency (WR) is a property that has implications on the hydrologic balance in affected soils. In semi‐arid areas where water supply is limited, even slight WR may play an important role in the infiltration and spatial distribution of precipitation into the soil. Acidic and sandy‐textured soils have been demonstrated to be more prone to develop WR, but there are studies reporting water repellent properties in other soil types. In the present study we investigated soil WR under four plant species in a semi‐arid area with a calcareous, medium‐textured forest soil. For this purpose, 160 soil samples were taken at micro‐sites under different species (Pinus halepensis, Quercus coccifera, Juniperus oxycedrus and Rosmarinus officinalis). Soil WR was measured with the water drop penetration time (WDPT) test on air‐dried samples. Samples with WDPT > 5 s were classified as water repellent. WR was present in 20% of the samples, and its persistence ranged mainly between 10 and 30 s. Under P. halepensis and Q. coccifera, WR occurred more frequently (40 and 30%, respectively) than under J. oxycedrus and R. officinalis (only 5% in both cases). In order to know the causes of the difference in occurrence of WR under the selected species and to establish relationships, soil organic matter (SOM) content and pH were measured for a selection of 66 samples, including all 32 water repellent and 34 wettable samples selected from those taken under the four species (n = 66). A negative relationship between WR and pH was found for all species. Moreover, in the case of P. halepensis soil samples, a positive correlation between WR and SOM content was found. A discriminant analysis allowed for the distinction between water repellent and wettable conditions in calcareous soils, based on the information provided by pH, SOM content and vegetation type. Soil pH turned out to be the most important parameter for discrimination. The hydrological and ecological implications from these results are discussed with special focus on the areas in the region extensively afforested with P. halepensis. Copyright © 2007 John Wiley & Sons, Ltd.
Water dynamics in drip and overhead sprinkler irrigated potato hills and development of dry zones
Authors: Cooley Eric T. , Lowery Birl , Kelling Keith A. , Wilner Seth 
Published: July 2007

AbstractIrrigation scheduling and nitrogen fertilizer placement and time of application have been studied extensively in an attempt to maximize utilization efficiency of nitrogen by potato (Solanum tuberosum L.) plants and reduce nitrate leaching to groundwater. Some researchers believe that drip irrigation, as compared to sprinkler irrigation, is more efficient in supplying irrigation water to potato hills. To investigate water distribution and movement through potato hills under drip and sprinkler irrigation time domain reflectometry (TDR) probes were installed into potato hills to monitor water content at 15‐min intervals at various positions in the potato hill. On average, water content values within the centre of the potato hill were greater under drip irrigation (average for 1996 and 1997 was 0·104 and 0·110 m3 m−3, respectively) as compared to sprinkler irrigation (average for 1996 and 1997 was 0·085 and 0·066 m3 m−3, respectively) where similar amounts of irrigation water were applied weekly. Water content values in the centre portion of the potato hill, where the greatest densities of roots occur, were greater under drip irrigation than sprinkler irrigation by an average of 0·032 m3 m−3 for values averaged over the two growing seasons. Concurrently, water content values were less in the furrow of drip irrigation than sprinkler irrigation by an average of 0·025 m3 m−3. Decreased water content in the centre portion of the potato hill under sprinkler irrigation became more prominent as the growing season progressed, resulting in hydrophobic soil conditions midway through the growing season. Copyright © 2007 John Wiley & Sons, Ltd.
Using spectral reflectance to document water stress in bermudagrass grown on water repellent sandy soils
Authors: Park Dara M. , Cisar John L. , Williams Karen E. , McDermitt Dayle K. , Miller William P. , Fidanza Michael A. 
Published: July 2007

AbstractTo conserve natural water resources, athletic fields may be mandated to follow phase water restrictions. In order to optimize irrigation reduction, early plant responses to water stress need to be identified to avoid loss in turfgrass performance and the requirement of additional irrigation to overcome water stress. Current irrigation scheduling based on using potential evapotranspiration (ET) and water stress indices are not suitable for all growing conditions, especially in the water repellent sand soils of South Florida. This experiment was conducted to use spectral reflectance as a means to document normal and progressive water stress in ‘Tifgreen’ bermudagrass (Cynodon dactylon (L.) Pers. X Cynodon transvaalensis Burtt Davy) grown on a native water repellent sand soil. Three consecutive trials were conducted, in which bermudagrass was subjected to either no irrigation until severe visual wilt (non‐irrigated) or irrigated daily (irrigated) over a dry down period. Visual assessment of turf quality and localized dry spot occurrence verified that bermudagrass receiving daily irrigation was not water‐limited and bermudagrass receiving no irrigation was experiencing increased water stress over time. An experimentally active near‐IR/red sensor was used to monitor changes in plant architecture as a means to determine early water stress. Monitoring near‐IR/red ratios determined mid‐day depression when water demand is at the highest as well as overnight rehydration in both bermudagrasses. At the end of the dry down period, pooled trial morning near‐IR/red ratios‐afternoon near‐IR/red ratios from non‐irrigated bermudagrass was significantly greater than irrigated bermudagrass (P = 0·0035), documenting severe water stress from the non‐irrigated bermudagrass. Spectral reflectance allows real‐time, site‐specific bermudagrass water stress evaluation before it is visually identifiable. Using spectral reflectance as an early warning detection tool can be used for better irrigation decisions including pre‐emptive irrigation to avoid water stress, compared to models based on predetermined ET and water stress indices. Copyright © 2007 John Wiley & Sons, Ltd.
Applicability of the Washburn theory for determining the wetting angle of soils
Authors: Czachor Henryk 
Published: July 2007

AbstractThe Washburn theory is frequently applied to determine the wetting angle of soils. It is based on the porous medium being characterized as a set of cylindrical, straight capillaries. It is clear that this is an oversimplification as real soil pores vary at least as regards two important features: cross‐section and tortuosity. In this study, a mathematical model of meniscus movement in a tortuous, sinusoidal shaped capillary was developed and the obtained analytical expressions for the wetting angle and for the pore radius were compared with the appropriate formula concerning the Washburn theory. The results demonstrate that the wetting angle of water in soil determined on the basis of the measured wetting front kinetics and of Washburn equations is likely to have an overestimated value due to the wavy, tortuous nature of inter‐soil grain pores. The above conclusion was confirmed by capillary rise experiments. Wetting angles of methyl alcohol and of water measured on flat glass were 0 and 27·4° , respectively. Apparent wetting angles calculated from capillary rise in powdered glass kinetics and Washburn equation were 70 and 83° respectively. If the pore structure characteristics of porous media are not taken into account the applicability of the Washburn theory for soil wettability estimation seems to be very limited. Copyright © 2007 John Wiley & Sons, Ltd.
Soil water repellency in a Japanese cypress plantation restricts increases in soil water storage during rainfall events
Authors: Kobayashi Masahiro , Shimizu Takanori 
Published: July 2007

AbstractForest soils in Japan are often water repellent. Substantial water repellency frequently occurs and impedes water infiltration into the soil matrix, but continuous overland flow is not necessarily observed because forest soils usually have macropores through which the water can enter the subsoil. Although this flow pattern may influence the manner of water storage in forest soils at the solum scale, field evidence has not yet indicated this process. We monitored soil water storage during natural rainfall events in a 60‐cm deep solum using time domain reflectometry (TDR) moisture sensors, and observed stained flow patterns in the soil following simulated rainfall containing a colour dye, on a slope planted with Japanese cypress (Chamaecyparis obtusa). The surface soil at the research plot exhibited strong water repellency at water contents lower than the threshold critical water content of 0·29 m3 m−3. Under dry antecedent moisture conditions, increases in soil water storage were small compared to the cumulative rainfall, despite the low wetness of the soil matrix. In contrast, under moderate moisture conditions, increases in the water content corresponded to the cumulative rainfall. Under dry conditions, rainwater may have entered the subsoil at a few limited locations connected with continuous vertical macropores, such as decayed root channels or interstructural voids. Therefore, the water seemed to bypass a large part of the soil matrix away from the macropores. Such preferential water flow was confirmed by the stained flow patterns after the rainfall simulation. The flow patterns visualized by the dye were discontinuous and scattered under dry conditions and diffuse under moderate moisture conditions. Repellency induced preferential flow led to restricted increases in solum scale water storage during rainfall events, reflecting a physical nonequilibrium in soil water storage. Copyright © 2007 John Wiley & Sons, Ltd.
Soil wettability, runoff and erodibility of major dry‐Mediterranean land use types on calcareous soils
Authors: Cerdà Artemi , Doerr Stefan H. 
Published: July 2007

AbstractThis study examines six land uses (pine woodland, long unburnt scrubland, recently burnt scrubland, orange grove, olive grove and cereal crop), typical for calcareous soils in a dry‐Mediterranean region such as eastern Spain, with regard to soil surface water repellency occurrence, hydrological response and erodibility. For each land use, we performed water drop penetration time (WDPT) tests and rainfall simulations respectively on in situ soils at ten replicate plots for extremely dry antecedent conditions in summer 2002 and for wet winter conditions, in early 2003 in the Canyoles river valley. In contrasts to what might have been expected, water repellency was absent or subcritical (WDPT < 5 s) under all land uses except pine, where slight repellency was found during summer (avg. WDPT 17 s). Higher levels of water repellency have been reported from some other Mediterranean type regions particularly after burning, and it appears that for some of the land uses examined here, the calcareous nature of the soils may restrict the development of water repellency. However, even the slight repellency observed under pine had a substantial effect on infiltration rates, generating more runoff on dry soil in summer than on moist soil in winter. Apart from water repellency, ground cover had a strong influence on soil hydrological response and was overall the most important factor influencing soil erodibility. The results suggest that, although the planting of pine woodland has been a favoured land management strategy in many parts of the Mediterranean basin, scrubland appears to be the more appropriate land cover type with regard to water use efficiency and soil conservation measures. Copyright © 2007 John Wiley & Sons, Ltd.
Temporal and spatial variations in topsoil water repellency throughout a crop‐rotation cycle on sandy soil in north‐central Portugal
Authors: Keizer J. J. , Doerr S. H. , Malvar M. C. , Ferreira A. J. D. , Pereira V. M. F. G. 
Published: July 2007

AbstractThe aim of this study is to improve our understanding of the temporal and spatial variations of soil water repellency, in particular those of agricultural lands where its economic and environmental impacts can be particularly severe. Variations in water repellency severity were studied with particular emphasis as to the role therein of the micro‐topographic differences between furrows and ridges.Topsoil water repellency was monitored over a 1‐year period at about monthly intervals and on some additional occasions in an agricultural field involving three land‐use phases (potatoes, maize, fallow) in the Dunas de Vagos area, north‐central Portugal. Water repellency severity was measured in situ at soil depths of 2–3 and 7–8 cm using the molarity of an ethanol droplet (MED) test, and accompanied by soil moisture measurements using a ThetaProbe. Under potatoes as well as maize, these measurements were carried out on ridges and in furrows separately.The results confirmed the transience of soil water repellency, which changed markedly within periods as short as 2 weeks. Although substantial changes in water repellency severity occurred, repellency was present over a large part of the monitoring period under potatoes, maize and fallow. Repellency severity was found to regularly differ significantly between furrows and ridges as well as between 2–3 and 7–8 cm depth. Soil moisture content was found to be an important factor, but by itself not sufficient to account for the observed temporal variations. Other temporally variable factors (e.g. microbial and root activity) might contribute to the variations in water repellency at this agricultural site under rotating crops. Copyright © 2007 John Wiley & Sons, Ltd.
Preliminary investigation of soil chemical and physical properties associated with type‐I fairy ring symptoms in turfgrass
Authors: Fidanza M. A. , Cisar J. L. , Kostka S. J. , Gregos J. S. , Schlossberg M. J. , Franklin M. 
Published: July 2007

AbstractFairy ring is a common disease of turfgrasses worldwide, and necrotic or severely injured turfgrass and soil water repellency are frequently observed in those turfgrass sites exhibiting type‐I fairy ring symptoms. The objective of this research was to evaluate soil chemical and physical properties associated with type‐I fairy ring symptoms in turfgrass. Soil samples were obtained from type‐I fairy ring symptoms on two golf course fairways and one lawn area. Soil analysis from all the three locations revealed concentrations of ammonium–nitrogen, potassium, and sulphur were statistically higher in soil underlying necrotic or bare zones versus soil in healthy turfgrass zones. Soil electrical conductivity (EC) also was higher, while volumetric soil water content was consistently lower in necrotic zones versus soil under healthy turfgrass. Soil water repellency was considered moderate to severe in necrotic zones and mostly wettable to subcritical repellency in soil underlying healthy turfgrass. Soil pH, total nitrogen, magnesium, calcium, cation exchange capacity (CEC), and organic matter content (OM) levels were not consistently different among necrotic and healthy turfgrass zones. The necrotic zones of those type‐I fairy ring areas in turfgrass were most likely associated with a combination of direct and indirect effects of the basidiomycete fungi on soil hydrophobicity and the accumulation of potentially phytotoxic compounds in the turfgrass root zone. Further research is needed to explore the interaction of basidiomycete fungi and the soil chemical and physical environment on turfgrass, and evaluate practices and strategies to control type‐I fairy ring symptoms in turfgrass. Copyright © 2007 John Wiley & Sons, Ltd.