Klaas Oostindie

Effect of drying temperature on the severity of soil water repellency

Soil water repellency is often recognized in surface layers of soils that dry out frequently. The degree of water repellency of a soil can be measured by using the water drop penetration time (WDPT) test on field-moist or dried samples, referred to as actual and potential water repellency, respectively. A soil layer is actually water repellent below and actually wettable above its critical soil water content. Findings of the present study indicated that the degree of potential water repellency might change with different drying temperatures. For four of the seven sandy soil sites studied in the Netherlands, potential water repellency was greater after drying at 65° C relative to drying at 25°C, whereas it decreased at two sites and remained unchanged at one. The most reliable estimate of water repellency was obtained from undried samples collected during dry periods. Wetting rate measurements illustrated that water repellency increasing as a result of high drying temperatures led to decreasing water absorption by samples. Micromorphological investigations indicated that high drying temperatures resulted in an increase in the

Exponential increase of publications related to soil water repellency

Soil water repellency is much more wide-spread than formerly thought. During the last decades, it has been a topic of study for soil scientists and hydrologists in at least 21 States of the USA, in Canada, Australia, New Zealand, Mexico, Colombia, Chile, Congo, Nepal, India, Hong Kong, Taiwan, China, Ecuador, Venezuela, Brazil, Mali, Japan, Israel, Turkey, Egypt, South Africa, Germany, The Netherlands, Spain, Portugal, United Kingdom, Denmark, Sweden, Finland, Poland, Slovakia, Russia, France, Italy, and Greece. Although, water repellent soils already have been indicated at the end of the nineteenth century, they have been discovered and studied in most countries in the last decades. Water repellency is most common in sandy soils with grass cover and in nature reserves, but has also been observed in loam, heavy clay, peat, and volcanic ash soils. From 1940 to 1970 research was focussed on identifying vegetation types responsible for inducing water repellency and on developing techniques to quantify the degree of water repellency. Of special interest has been the effects of wildfire on the development of soil water repellency and its consequences for soil erosion. Due to increasing concern over the threat to surface and groundwater posed by the use of agrichemicals and organic fertilisers, studies on water repellent soils have also been focused on its typical flow behavior with runoff and the existence of preferential flow paths. Since the end of the 1950s, wetting agents and clay amendments have been studied to ameliorate water repellent soils. Since 1883, more than 1200 articles related to soil water repellency have been published in journals, reports, and theses. An exponential increase in number of publications started in 1960, resulting in an average of 200 publications per 5 years.

A new wireless underground network system for continuous monitoring of soil water contents

A new stand-alone wireless embedded network system has been developed recently for continuous monitoring of soil water contents at multiple depths. This paper presents information on the technical aspects of the system, including the applied sensor technology, the wireless communication protocols, the gateway station for data collection, and data transfer to an end user Web page for disseminating results to targeted audiences. Results from the first test of the network system are presented and discussed, including lessons learned so far and actions to be undertaken in the near future to improve and enhance the operability of this innovative measurement approach.

Water repellency under natural conditions in sandy soils of southern Spain

The occurrence and consequences of fire-induced water repellency have been studied in several regions of Spain since 1989. The occurrence of water repellency formed under natural conditions, however, has only been described for a few areas in Spain since 1998. The purpose of the present study was to investigate the severity of naturally occurring water repellency in the sandy soils of the Natural Park of Donana in southern Spain. The persistence and degree of soil water repellency were measured on field-moist and dried sandy soil samples taken beneath Pinus pinea trees. Around 50% of the field-moist soil samples taken at 0–0.10 m depths exhibited (actual) water repellency. Potential water repellency, measured after drying the samples at 60°C, showed for 68% of the samples slight to extreme water repellency. The organic matter content was found to be positively correlated with persistence and with degree of potential water repellency.

Soil water repellency in north-eastern Greece with adverse effects of drying on the persistence

Many soils 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 often leads to the development of unstable wetting and preferential flow paths. In the present study the persistence of water repellency was examined on samples from topsoils in Thrace, north-eastern Greece, using the Water Drop Penetration Time (WDPT) test. The soil samples were collected from agricultural fields throughout the prefectures of Xanthi and Rodopi. Six sites were selected for intensive sampling of water repellency and soil moisture content in transects. Water repellency was measured on field-moist soil samples and after drying the samples at increasing temperatures, to study the influence of drying temperature on the persistence of soil water repellency. Measurements of soil samples taken in agricultural fields under different crops, e.g. winter wheat, tobacco, clover, olive groves, kiwi fruit, and vineyards, in the area of Thrace, revealed that 45% of the locations exhibited actual water repellency during dry periods. Drying of samples from the Sostis site resulted in wettable soil, whereas drying of samples from the Mitriko site increased repellency. Therefore, water repellency should preferably be measured on samples taken in the field under dry conditions in order to reveal and determine the highest persistence of water repellency that might occur in the field.

Methods for determining soil water repellency on field‐moist samples

In this paper we describe a simple and quick method for determining the presence of water repellency in a soil by using a small core sampler (1.5 cm in diameter, 25 cm long) and applying the water drop penetration time (WDPT) test at different depths on the sandy soil cores. Obtained results provide spatial distribution patterns of water repellency in a soil profile, demonstrating seasonal changes in repellency. An advantage of the method is that the soil is not disturbed by the sampling. For assessment of the persistence of water repellency in strongly to extremely water repellent soils, and for determination of the critical soil water contents, the WDPT test and volumetric water content determinations should preferably be performed in the laboratory.

A new modelling approach to simulate preferential flow and transport in water repellent porous media: Model structure and validation

Water repellent soil and surface layers exhibit a complex flow and transport mechanism. Knowledge of the underlying principles is essential, for instance, to simulate water availability for crops and to estimate leaching potentials of agrichemicals. The present study aims to introduce and apply a new modelling approach to simulate preferential flow and transport in water repellent porous media, and to test the model on basis of an extensive field tracer experiment. The process of preferential flow and transport has been incorporated in the well-known SWAP model and applied to field data of tracer transport through a water repellent sandy soil in the Netherlands. Flow concept and model structure have been outlined, and simulation results presented. Results indicated early arrival times of bromide tracer in the subsoil in the case where preferential flow has been taken into account in the model. Comparison of measured and computed bromide concentration profiles and bromide recovery rates show close resemblances. Several strategies to alleviate soil water repellency and prevent the occurrence of preferential flow and transport processes are highlighted, such as irrigation scheduling, clay additions, and application of surfactants.

Effects of surfactant treatments on the wettability of a water repellent grass-covered dune sand

The objective of this study was to evaluate the effectiveness of the surfactant formulation Primer604 for amelioration and management of soil water repellency in grass-covered dune sand. The soil is severely to extremely water repellent to a depth of >0.50 m during dry periods. Primer604 was applied 12 times between 22 April and 23 November 1999. During that period, soil samples were taken in the untreated and treated plot— 8 times in transects and 2 times in soil blocks. A total of 4950 samples were collected for assessment of the actual water repellency and for the spatial and temporal variability of the water content of the soil. Resistance to wetting was determined by measuring the wetting rate of field-moist samples. Measurements of water repellency revealed that applications of Primer604 resulted in less persistent water repellency in the surface layer to a depth of 0.05 m. No effects were observed deeper in the soil profile, likely due to adsorption of the surfactant material in the surface layer. In the surface layer (0-0.025 and 0.025-0.05 m), the critical soil water content below which the soil is actually water repellent in the field was lowered distinctly by the application of Primer604, potentially due to coating of water repellent particle surfaces by the surfactant. This suggests that the surface layer (0-0.05 m) in the Primer604-treated soil can dry to lower water contents than in the untreated soil before water repellency is induced. The thatch layer (0-0.025 m) of the treated soil was often found to have slightly higher water contents than of the untreated soil. The surfactant did not equalise the uneven moisture distribution in the soil below the surface layer (0-0.05 m). Primer604 applications increased the wetting rate of field-moist samples from the thatch layer. This may result in a more effective wetting of the root-zone during rain events or irrigation, and a reduction in runoff.

The effect of soil surfactants on soil hydrological behavior, the plant growth environment, irrigation efficiency and water conservation

The effect of soil surfactants on soil hydrological behavior, the plant growth environment, irrigation efficiency and water conservation Soil water repellency causes at least temporal changes in the hydrological properties of a soil which result in, among other things, suboptimal growing conditions and increased irrigation requirements. Water repellency in soil is more widespread than previously thought and has been identified in many soil types under a wide array of climatic conditions worldwide. Consequences of soil water repellency include loss of wettability, increased runoff and preferential flow, reduced access to water for plants, reduced irrigation efficiency, increased requirement for water and other inputs, and increased potential for non-point source pollution. Research indicates that certain soil surfactants can be used to manage soil water repellency by modifying the flow dynamics of water and restoring soil wettability. This results in improved hydrological behavior of those soils. Consequently, the plant growth environment is also improved and significant water conservation is possible through more efficient functioning of the soil. Vplyv povrchovo aktívnych látok na hydrologické procesy v pôde, rast rastlín, závlahy a retenciu vody v pôde Vodoodpudivosť pôdy spôsobuje prinajmešom dočasné zmeny v hydrologických vlastnostiach pôdy, ktoré okrem iného môžu viesť k suboptimálnym podmienkam rastu rastlín a k zvýšenej potrebe závlah. Vodoodpudivosť pôdy je rozšírenejší jav, ako sa pôvodne predpokladalo; bola identifikovaná v mnohých pôdnych typoch a klimatických podmienkach na celom svete. Dôsledkom vodoodpudivosti pôdy je strata zmáčavosti, zvýšený povrchový odtok a preferenčné prúdenie, znížená dostupnosť vody a iných vstupov pre rastliny, znížený účinok závlah, zvýšené požiadavky na vodu a iné vstupy, ako aj zvýšené riziko plošného znečistenia. Výskum naznačuje, že niektoré povrchovo aktívne látky (soil surfactants) môžu upraviť vodoodpudivosť pôdy obnovením omáčania a modifikáciou dynamiky vody. Výsledkom je zlepšenie hydrologických vlastností pôdy. Podobne, výsledkom je zlepšenie prostredia pre rast rastlín, zvýšenie retencie vody v pôde a teda aj efektívnejšia funkcia pôdy.

Evaluation of vertical and lateral flow through agricultural loessial hillslopes using a two-dimensional computer simulation model

On four hill-slopes in the loess region of the Netherlands pressure heads were monitored during rain events with time intervals of five minutes. Water flow through these hill-slopes during erosive rain events in summer and winter was simulated two-dimensionally. These simulations showed that vertical flow is dominant during rain events, whereas lateral water transport is of minor importance. The average lateral water movement varied between 1.6 and 4.7% of the total water displacement. Therefore, it was decided to incorporate a one-dimensional water flow module into the soil erosion and hydrological model LISEM.