Received: 26 February 2024

Accepted: 27 February 2024

DOI: 10.1002/vzj2.20327
Vadose Zone Journal

EDITORIAL
S p e c i a l S e c t i o n : Tr i b u t e t o R i e n v a n G e n u c h t e n , R e c i p i e n t o f t h e 2 0 2 3 Wo l f P r i z e f o r A g r i c u l t u r eSpecial Issue: Tribute to Rien van Genuchten, recipient of the2023 Wolf Prize for Agriculture
This Special Issue (SI) is dedicated to Dr. Rien van Genuchten(Martinus Th. van Genuchten, hereafter called Rien) as a tribute to him for being awarded the very prestigious international
Wolf Prize for Agriculture. The Wolf Foundation awards
prizes annually to outstanding scientists and artists worldwide
for their excellent achievements in the interest of humanity and friendly relations among peoples, regardless of theirbackground (About the Wolf Foundation—Wolf Foundation[wolffund.org]). Many would state that receiving this Prize isanalogous to being awarded a Nobel Prize, as both recognize
scientists for their impacts on society. For one of our colleagues, to be selected for this award is especially rewarding as
it recognizes the relevance of soil physics to the field of agriculture and environmental sciences globally. Rien created amuch-needed scientific basis for understanding fluid flow andcontaminant transport processes in unsaturated soils, reshaping the disciplines of soil physics and vadose zone hydrology.
Vadose zone hydrology would be unthinkable without his
many contributions, which established links between agriculture, soil science, geology, environmental sciences, andhydrologic engineering. The SI targets articles from authors
who have either collaborated with Rien or built their research
program based on his many contributions to the field of Soil
Physics and Vadose Zone Hydrology. It also includes selected
contributions by scientists from other disciplines who applied
the concepts developed by Rien, addressing various relevant
environmental issues.

1

RESEARCH ACCOMPLISHMENTS

There have been very few contemporary colleagues in soil
science who have made such a huge impact on the field ofsoil physics and the careers of so many students and earlycareer soil physicists than Rien. His influence was perhapsnot so predictable early on when he was a graduate student in
the early 70s under the mentorship of Pete Wierenga at New
Mexico State, Las Cruces. As Rien explained in his autobiography (van Genuchten, 2024), Pete was not so impressed withhis experimental skills, letting him instead tinker with mathematical models that can better represent physical transport
processes in soils. His proficiency in modeling was alreadyevident in his first peer-reviewed paper (van Genuchtenet al., 1974), where he used the CSMP computer language(as he learned this very early software for solving differential equations while studying at Wageningen University
with C. T. de Wit; Research of the Plant Production SystemsGroup—WUR) to simulate the nonequilibrium transport ofpesticides in soils as well as their parametric estimations using
column studies. Subsequently, under the supervision of Drs.
Pinder and Gray at Princeton University, Rien developed afinite element model to solve multidimensional multiphaseflow.
He then went on to the USDA-ARS Soil Salinity Laboratory on the UC Riverside campus, further developing andadvancing algorithms with numerous visiting scientists andlab staff to improve soil water and chemical transport solutions. Early on, at the US Salinity Lab, he published theparametric model for unsaturated soil hydraulic properties(van Genuchten, 1980). Rien continues to receive enormous
recognition for this research paper as this model provided
enormous computational time savings, thus allowing efficient numerical solutions to the highly nonlinear unsaturated
water flow equation. Moreover, the so-called van Genuchten–Mualem (vG–M) parametric expressions have been shownto fit most experimental soil hydraulic data, thus making
them attractive in many vadose zone applications. After being
devoted to mostly theoretical research in the first half of
his scientific career, Rien committed to applying his work
to many different relevant problems that could be addressedwith his modeling advancements, such as pesticide, pharmaceutical, nutrient, pathogen, and colloid transport processes,multicomponent geochemical and radionuclide transport, root
water uptake and soil salinity, among others. He continued working on many of these applications after retiringfrom the US Salinity Laboratory at the Federal Universityof Rio de Janeiro in Brazil and Utrecht University in theNetherlands.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original
work is properly cited.
© 2024 The Authors. Vadose Zone Journal published by Wiley Periodicals LLC on behalf of Soil Science Society of America.
Vadose Zone J. 2024;23:e20327.
https://doi.org/10.1002/vzj2.20327

wileyonlinelibrary.com/journal/vzj2

1 of 3

Vadose Zone Journal

An extensive summary of his research accomplishments
is further written in Rien’s autobiography (van Genuchten,2024). In addition to the highly cited landmark article on thevG–M model (>32,000 citations), more than 180 of Rien’s
research papers and reports have been cited at least 100 times.
To date, his research has led to an astounding total numberof more than 100,000 citations (Google Scholar; a milestone
surely to be reached before this introduction is published).
While such numbers are not the sole determinant of the scientific impact of his work, the sheer magnitude of his citation
numbers is mind-boggling.

2PROFESSIONAL ACHIEVEMENTS

While Rien’s scientific contributions go without question,
his impact on people’s professional careers is even moreunprecedented. By recruiting the best and brightest students
and scientists, he consistently cultivated their career development options and expertise through his encouragement,
enthusiasm, and support. Especially remarkable has been his
support of students and scientists from non-Western countries.
In doing so, he provided opportunities that were otherwise
not available to them at the time. Throughout his career, hehosted and inspired approximately 70 visiting scientists andserved on many PhD committees across all continents, manyof whom developed successful careers. Graduates of Rien’s“Soil Physics Without Borders” movement hold faculty positions at about 10 US universities, and about twice as many
have found similar positions abroad.
Rien was elected a Fellow of AAAS, AGU, ASA, andSSSA, and has received many other major awards, such as
the Don and Betty Kirkham Medal and the EGU Dalton
Medal. In 2020, he was presented with the very prestigious
AGU Horton Medal, and most recently, he was elected tothe US National Academy of Engineering. Due to his landmark contributions and leadership in the agricultural sciences,
specifically on theory development and applications in agriculture and soil hydrology, Rien was awarded the 2023 Wolf
Prize for reshaping the disciplines of soil physics and vadosezone hydrology through “his groundbreaking work in understanding water flow and predicting contaminant transport insoils.”

3INTERDISCIPLINARY FOCI

In part because of the advanced model applications developed by Rien, knowledge of dynamic soil processes has
rapidly evolved in the past decades, thus enhancing researchcollaborations between disciplines of soils and hydrology,engineering, biology (plant and microbial sciences), climate science, among others. Most illustrative has been themovement since the 1990s for soil physics to transcend its

EDITORIAL

disciplinary field to vadose zone research, leading to the publication of the Vadose Zone Journal (VZJ) in 2002, strongly
advocated by Rien and colleagues (van Genuchten, 2002).
His efforts in reaching the broader scientific community
were achieved by serving as the founding editor of VZJ, aninterdisciplinary journal of the Tri-Societies (American Society of Agronomy, Crop Science Society of American, andSoil Science Society of America), broadly linking soil science
with agriculture, hydrology, engineering, geology, ecology,and environmental sciences. The name “Vadose Zone
Journal” was selected to clearly show the intent of VZJ to seek
contributions and readership from across a broad range of disciplines, in addition to the soil and agricultural communities.
The rapid acceptance of VZJ within the scientific community has been a recognition that vadose zone processes playa prominent role in many interdisciplinary environmental andresource management issues.

4MULTIDISCIPLINARY NATURE OF
THE SIAs articulated in the previous section, the continued development of multidisciplinary collaborations has paved the way tofurther disciplinary contributions to broader societal issues,potentially leading to transdisciplinary applications (Hopmans, 2020). In the spirit of the scope of VZJ and the needto increase multidisciplinary soil investigations, this SI is an
excellent example of the broad range of applications, therebyreflecting the impact of Rien’s career. The desire for one’s
research to impact society is also well articulated by him inthe closing remarks of his autobiography (van Genuchten,2024), by stating that “I have become more concerned about
all the unfortunate troubles we face on this planet, such as theenvironmental problems and climate change, and the enormous political and socio-economic problems all over theworld. Because our planet is faced with so many environmental problems, it is not easy to choose the best area in one’sresearch.”
Unsurprisingly, many SI contributions discuss the treatment of soil hydraulic properties and their advanced characterization and/or application for a wide range of soils, including those ill-behaved or nonideal that the van Genuchten
vG–M model cannot describe well. Other papers contribute tofurther illuminating soil physical flow and chemical transport
processes at various scales, further advancing his early computer modeling frameworks and applications beyond what one
could have surmised at the time. Some SI papers address theneed for further scientific investigations of the transport ofspecific chemical species, such as radioactive isotopes andheavy metals in soils and the vadose zone. In contrast, othercontributors focused on soil salinity impacts on agriculturalproduction, thus illustrating Rien’s broad research at the US
Salinity Laboratory.

15391663, 2024, 4, Downloaded from https://acsess.onlinelibrary.wiley.com/doi/10.1002/vzj2.20327 by Cochrane Czech Republic, Wiley Online Library on [21/07/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

2 of 3

In summary, reflecting on the many published works
herein, the Tribute is an excellent example of the enormous impact Rien has had on the direction of soil science
research, specifically by introducing mathematical modelingof unsaturated soil water flow and chemical transport in thesoil science literature, thereby making computer solutions
widely accessible and allowing the wider professional community to significantly advance the scientific field. To muchof Rien’s credit, his model solutions accelerated the rate bywhich new theories and applications of unsaturated waterflow and chemical transport were adopted in the agricultural,hydrological, and environmental sciences. During his 50-yearcareer, Rien transformed the broad fields of soil physics andvadose zone hydrology, which are central to modern agricultural operations, environmental assessment, and climate
science.
Rien’s contributions transcend his scientific achievements.
He embodies genuine mentorship and collaborative growth.
His remarkable ability to elevate the work of early-career
researchers and his support for their career advancement
exemplify a dedication to nurturing the next generation ofvadose zone scientists. Apart from research, Rien is also
passionate about teaching. He continues to make himselfavailable by delivering guest lectures that enrich the education of students, extending his already broad impact. Rien has
instilled in researchers across all stages of their careers the values of collegiality, the importance of fostering opportunities
for others, and the power of a positive spirit. His commitment
to research and teaching, unrelenting collegial support, andunusual humility inspire us all.
AU T H O R C O N T R I B U T I O N S
Jan Hopmans: Conceptualization; writing—original draft.
Binayak Mohanty: Conceptualization; writing—review andediting. Jirka Simunek: Conceptualization; writing—reviewand editing.
AC K N OW L E D G M E N T S
The co-editors of this SI accredit Dr. Jaivime Evaristo ofUtrecht University for his editing of the manuscript, espe-Vadose Zone Journal

3 of 3cially the last paragraph related to Rien’s contributions to thementorship of students and other early-career scientists.
Jan W. Hopmans1Jiří Šimůnek2
Binayak P. Mohanty3
1 Department of Land, Air and Water Resources, Universityof California, Davis, Davis, California, USA
2 Department of Environmental Sciences, University ofCalifornia, Riverside, Riverside, California, USA
3 Biological and Agricultural Engineering, Texas A&M

University, College Station, Texas, USACorrespondence
Jan W. Hopmans, 1120 NW 17th St, Corvallis, OR 97330,
USA. Email: janwhopmans@gmail.com
ORCID
Jan W. Hopmans https://orcid.org/0000-0002-4807-2172
Jiří Šimůnek https://orcid.org/0000-0002-0166-6563
Binayak P. Mohanty https://orcid.org/0000-0001-93817279
REFERENCES
Hopmans, J. W. (2020). Transdisciplinary soil hydrology. Vadose
Zone Journal, 19(1), Article e20085. https://doi.org/10.1002/vzj2.
20085
van Genuchten, M. Th. (1980). A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Science
Society of America Journal, 44(5), 892–898. https://doi.org/10.2136/
sssaj1980.03615995004400050002x
van Genuchten, M. Th. (2024). Rien van Genuchten: A short autobiography. Vadose Zone Journal, (in press). https://acsess.onlinelibrary.
wiley.com/doi/full/10.1002/vzj2.20322
van Genuchten, M. Th. (2002). Letter from the editor. Vadose Zone
Journal, 1(1), 1–2. https://doi.org/10.2136/vzj2002.1000
van Genuchten, M. Th., Davidson, J. M., & Wierenga, P. J. (1974).
An evaluation of kinetic and equilibrium equations for the predictionof pesticide movement through porous media. Soil Science Societyof America Journal, 38(1), 29–35. https://doi.org/10.2136/sssaj1974.
03615995003800010016x

15391663, 2024, 4, Downloaded from https://acsess.onlinelibrary.wiley.com/doi/10.1002/vzj2.20327 by Cochrane Czech Republic, Wiley Online Library on [21/07/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

EDITORIAL