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Approximately 1 billion ha of the global land surface is currently salt-affected, representing about 7% of the earth's land surface. Whereas most of it results from natural geochemical processes, an estimated 30% of irrigated lands globally are salt-affected through secondary human-induced salinization. Application of lower quality, alternative irrigation water is further threatening expansion of the areal extent of soil salinity, in addition to climate change causing increases of salt-water intrusion in coastal areas and increasing crop water requirements. The reduced availability of freshwater resources for irrigation, the continued reduction of the world's cultivated agricultural area by land degradation and urbanization, in conjunction with a growing world population further complicates the problem seeking sustainable solutions. This scoping review prioritizes critical knowledge gaps and makes recommendations for 10 priorities in soil salinity research toward a sustainable and productive agricultural system for a food-secure future world. We also include basin-specific case studies that illustrate progress of the world's major irrigated areas in addressing impacts of soil salinization. By identifying research priorities, we seek to accelerate enhanced research funding to bring new knowledge and innovative solutions toward mitigation of soil salinity impacts. We further want to inspire the science community to develop new directions in salinity research.
Jan W. Hopmans; A.S. Qureshi; I. Kisekka; R. Munns; S.R. Grattan; P. Rengasamy; A. Ben-Gal; S. Assouline; M. Javaux; P.S. Minhas; P.A.C. Raats; T.H. Skaggs; G. Wang; Q. De Jong Van Lier; H. Jiao; R.S. Lavado; N. Lazarovitch; B. Li; E. Taleisnik. Critical knowledge gaps and research priorities in global soil salinity. Advances in Agronomy 2021, 169, 1 -191.
AMA StyleJan W. Hopmans, A.S. Qureshi, I. Kisekka, R. Munns, S.R. Grattan, P. Rengasamy, A. Ben-Gal, S. Assouline, M. Javaux, P.S. Minhas, P.A.C. Raats, T.H. Skaggs, G. Wang, Q. De Jong Van Lier, H. Jiao, R.S. Lavado, N. Lazarovitch, B. Li, E. Taleisnik. Critical knowledge gaps and research priorities in global soil salinity. Advances in Agronomy. 2021; 169 ():1-191.
Chicago/Turabian StyleJan W. Hopmans; A.S. Qureshi; I. Kisekka; R. Munns; S.R. Grattan; P. Rengasamy; A. Ben-Gal; S. Assouline; M. Javaux; P.S. Minhas; P.A.C. Raats; T.H. Skaggs; G. Wang; Q. De Jong Van Lier; H. Jiao; R.S. Lavado; N. Lazarovitch; B. Li; E. Taleisnik. 2021. "Critical knowledge gaps and research priorities in global soil salinity." Advances in Agronomy 169, no. : 1-191.
Low-cost, accurate soil water sensors combined with wireless communication in an internet of things (IoT) framework can be harnessed to enhance the benefits of precision irrigation. However, the accuracy of low-cost sensors (e.g., based on resistivity or capacitance) can be affected by many factors, including salinity, temperature, and soil structure. Recent developments in wireless sensor networks offer new possibilities for field-scale monitoring of soil water content (SWC) at high spatiotemporal scales, but to install many sensors in the network, the cost of the sensors must be low, and the mechanism of operation needs to be robust, simple, and consume low energy for the technology to be practically relevant. This study evaluated the performance of a resistivity–capacitance-based wireless sensor (Sensoterra BV, 1018LE Amsterdam, Netherlands) under different salinity levels, temperature, and soil types in a laboratory. The sensors were evaluated in glass beads, Oso Flaco sand, Columbia loam, and Yolo clay loam soils. A nonlinear relationship was exhibited between the sensor measured resistance (Ω) and volumetric soil water content (θ). The Ω–θ relationship differed by soil type and was affected by soil solution salinity. The sensor was extremely sensitive at higher water contents with high uncertainty, and insensitive at low soil water content accompanied by low uncertainty. The soil solution salinity effects on the Ω–θ relationship were found to be reduced from sand to sandy loam to clay loam. In clay soils, surface electrical conductivity (ECs) of soil particles had a more dominant effect on sensor performance compared to the effect of solution electrical conductivity (ECw). The effect of temperature on sensor performance was minimal, but sensor-to-sensor variability was substantial. The relationship between bulk electrical conductivity (ECb) and volumetric soil water content was also characterized in this study. The results of this study reveal that if the sensor is properly calibrated, this low-cost wireless soil water sensor has the potential of improving soil water monitoring for precision irrigation and other applications at high spatiotemporal scales, due to the ease of integration into IoT frameworks.
Srinivasa Rao Peddinti; Jan W. Hopmans; Majdi Abou Najm; Isaya Kisekka. Assessing Effects of Salinity on the Performance of a Low-Cost Wireless Soil Water Sensor. Sensors 2020, 20, 7041 .
AMA StyleSrinivasa Rao Peddinti, Jan W. Hopmans, Majdi Abou Najm, Isaya Kisekka. Assessing Effects of Salinity on the Performance of a Low-Cost Wireless Soil Water Sensor. Sensors. 2020; 20 (24):7041.
Chicago/Turabian StyleSrinivasa Rao Peddinti; Jan W. Hopmans; Majdi Abou Najm; Isaya Kisekka. 2020. "Assessing Effects of Salinity on the Performance of a Low-Cost Wireless Soil Water Sensor." Sensors 20, no. 24: 7041.
In this paper, I present an evolutional pathway from disciplinary towards transdisciplinary science and research and offer contemporary examples of interdisciplinary research in soil hydrology. I further explore exciting opportunities that can lead to transdisciplinary research (TDres), as society demands for our science expertise to be increasingly involved in developing solutions in global issues of sustainability, food and water security, as well as in the decision‐making process. By way of TDres involvement in public policy, the scientist is going to be working in the trans‐science domains for which (s)he is likely not very prepared. Recommendations are presented to better train students and early‐career scientists so that they can be effective in participating in TDres and communicating their scientific knowledge to relevant stakeholders, the public, and decision makers as part of the policy‐making process.
Jan W. Hopmans. Transdisciplinary soil hydrology. Vadose Zone Journal 2020, 19, 1 .
AMA StyleJan W. Hopmans. Transdisciplinary soil hydrology. Vadose Zone Journal. 2020; 19 (1):1.
Chicago/Turabian StyleJan W. Hopmans. 2020. "Transdisciplinary soil hydrology." Vadose Zone Journal 19, no. 1: 1.
The soil is the most upper part of the vadose zone, subject to fluctuations in water and chemical content by infiltration and leaching, water uptake by plant roots, and evaporation from the soil surface. It is the most dynamic, as changes occur at increasingly smaller time and spatial scales when moving from the groundwater toward the soil surface. Scientists are becoming increasingly aware that soils make up a critically important component of the earth’s biosphere, not only because of their food production function but also as the safe-keeper of local, regional, and global environmental quality. We first review soil physical properties and transport processes in soils. We then describe plant water and nutrient uptake modeling concepts in stressed soil environmental conditions and conclude with a comprehensive modeling framework for the simulation of water and nutrient transport in soils.
Jan W. Hopmans. Soil Physical Properties, Processes, and Associated Root-Soil Interactions. Dryland Ecohydrology 2019, 49 -69.
AMA StyleJan W. Hopmans. Soil Physical Properties, Processes, and Associated Root-Soil Interactions. Dryland Ecohydrology. 2019; ():49-69.
Chicago/Turabian StyleJan W. Hopmans. 2019. "Soil Physical Properties, Processes, and Associated Root-Soil Interactions." Dryland Ecohydrology , no. : 49-69.
Although only representing 0.05% of global freshwater, or 0.001% of all global water, soil water supports all terrestrial biological life. Soil moisture behaviour in most models is constrained by hydraulic parameters that do not change. Here we argue that biological feedbacks from plants, macro‐fauna and the microbiome influence soil structure, and thus the soil hydraulic parameters and the soil water content signals we observe. Incorporating biological feedbacks into soil hydrological models is therefore important for understanding environmental change and its impacts on ecosystems. We anticipate that environmental change will accelerate and modify soil hydraulic function. Increasingly we understand the vital role that soil moisture exerts on the carbon cycle and other environmental threats such as heatwaves, droughts and floods, wildfires, regional precipitation patterns, disease regulation and infrastructure stability, in addition to agricultural production. Biological feedbacks may result in changes to soil hydraulic function that could be irreversible, resulting in alternative stable states (ASS) of soil moisture. To explore this, we need models that consider all the major feedbacks between soil properties and soil‐plant‐faunal‐microbial‐atmospheric processes, which is something we currently do not have. Therefore, a new direction is required to incorporate a dynamic description of soil structure and hydraulic property evolution into soil‐plant‐atmosphere, or land surface, models that consider feedbacks from land use and climate drivers of change, so as to better model ecosystem dynamics. This article is protected by copyright. All rights reserved.
David A. Robinson; Jan Hopmans; Vilim Filipović; Martine Van Der Ploeg; Inma Lebron; Scott B. Jones; Sabine Reinsch; Nick Jarvis; Markus Tuller. Global environmental changes impact soil hydraulic functions through biophysical feedbacks. Global Change Biology 2019, 25, 1895 -1904.
AMA StyleDavid A. Robinson, Jan Hopmans, Vilim Filipović, Martine Van Der Ploeg, Inma Lebron, Scott B. Jones, Sabine Reinsch, Nick Jarvis, Markus Tuller. Global environmental changes impact soil hydraulic functions through biophysical feedbacks. Global Change Biology. 2019; 25 (6):1895-1904.
Chicago/Turabian StyleDavid A. Robinson; Jan Hopmans; Vilim Filipović; Martine Van Der Ploeg; Inma Lebron; Scott B. Jones; Sabine Reinsch; Nick Jarvis; Markus Tuller. 2019. "Global environmental changes impact soil hydraulic functions through biophysical feedbacks." Global Change Biology 25, no. 6: 1895-1904.
Sensor networks within the Southern Sierra Critical Zone Observatory (SSCZO) and Kings River Experimental Watersheds (KREW) document changes in the water cycle spanning the west slope of the southern Sierra Nevada in California. The networks were established to document water dynamics throughout the critical zone spanning profile, hillslope, catchment, and watershed scales at key locations that reflect systematic differences in bioclimatic conditions imposed by a strong elevation gradient. The critical zone observatory attempts to constrain the hydrologic budget via representative measurements of streamflow, eddy flux covariance, snow depth, meteorological conditions, and water content and water potential in soil and deep regolith. These measurements reveal the complexity of interactions among all aspects of the water balance (runoff, storage, evapotranspiration [ET], and precipitation) through daily, seasonal, and annual timescales. Multiyear drought, catastrophic wildfires, insect outbreaks, and disease have caused widespread tree mortality in the Sierra Nevada. These disturbances offer a window into the future for this region, which is expected to undergo significant change in response to global warming. This hydrological observatory provides valuable hydrometric attributes and fluxes across the stream–groundwater–vadose zone–soil–vegetation–atmosphere continuum. Copyright © 2018. . Copyright © by the Soil Science Society of America, Inc.
Anthony (Toby) O’Geen; Mohammad Safeeq; Joseph Wagenbrenner; Erin Stacy; Peter Hartsough; Scott Devine; Zhiyaun Tian; Ryan Ferrell; Mike Goulden; Jan Hopmans; Roger Bales. Southern Sierra Critical Zone Observatory and Kings River Experimental Watersheds: A Synthesis of Measurements, New Insights, and Future Directions. Vadose Zone Journal 2018, 17, 180081 .
AMA StyleAnthony (Toby) O’Geen, Mohammad Safeeq, Joseph Wagenbrenner, Erin Stacy, Peter Hartsough, Scott Devine, Zhiyaun Tian, Ryan Ferrell, Mike Goulden, Jan Hopmans, Roger Bales. Southern Sierra Critical Zone Observatory and Kings River Experimental Watersheds: A Synthesis of Measurements, New Insights, and Future Directions. Vadose Zone Journal. 2018; 17 (1):180081.
Chicago/Turabian StyleAnthony (Toby) O’Geen; Mohammad Safeeq; Joseph Wagenbrenner; Erin Stacy; Peter Hartsough; Scott Devine; Zhiyaun Tian; Ryan Ferrell; Mike Goulden; Jan Hopmans; Roger Bales. 2018. "Southern Sierra Critical Zone Observatory and Kings River Experimental Watersheds: A Synthesis of Measurements, New Insights, and Future Directions." Vadose Zone Journal 17, no. 1: 180081.
Leaching is an important aspect of irrigation water management, as it must be minimal to save available irrigation water resources, prevent shallow groundwater tables, and reduce nutrient loadings to the groundwater. However, at the same time, leaching should be sufficient to maintain root zone salinity levels below the threshold to prevent yield reduction. Therefore, monitoring leaching is the key component in evaluation and optimization of irrigation water management practices. Water balance (WB) is a common approach used to estimate leaching in agricultural fields and was applied in this study to assess field-scale leaching and the associated uncertainties for an almond orchard under drip and micro-sprinkler irrigation systems. In this study, we showed that change is soil water storage (ΔS) is highly influenced by the extent of monitoring depth, the location and number of monitoring points. Local measurement of WB parameters showed that leaching is highly variable across the field, thereby introducing considerable uncertainty on estimated leaching using WB approach. It was also shown that unknown input of water through fog interception added to the complexity of closing water balance at field scale.
Isaya Kisekka; Maziar M. Kandelous; Blake Sanden; Jan W. Hopmans. Uncertainties in leaching assessment in micro-irrigated fields using water balance approach. Agricultural Water Management 2018, 213, 107 -115.
AMA StyleIsaya Kisekka, Maziar M. Kandelous, Blake Sanden, Jan W. Hopmans. Uncertainties in leaching assessment in micro-irrigated fields using water balance approach. Agricultural Water Management. 2018; 213 ():107-115.
Chicago/Turabian StyleIsaya Kisekka; Maziar M. Kandelous; Blake Sanden; Jan W. Hopmans. 2018. "Uncertainties in leaching assessment in micro-irrigated fields using water balance approach." Agricultural Water Management 213, no. : 107-115.
The Century Experiment at the Russell Ranch Sustainable Agriculture Facility at the University of California, Davis provides long‐term agroecological data from row crop systems in California's Central Valley starting in 1993. The Century Experiment was initially designed to study the effects of a gradient of water and nitrogen availability on soil properties and crop performance in ten different cropping systems to measure tradeoffs and synergies between agricultural productivity and sustainability. Currently systems include 11 different cropping systems–consisting of four different crops and a cover crop mixture–and one native grass system. This paper describes the long‐term core data from the Century Experiment from 1993–2014, including crop yields and biomass, crop elemental contents, aerial‐photo‐based Normalized Difference Vegetation Index data, soil properties, weather, chemical constituents in irrigation water, winter weed populations, and operational data including fertilizer and pesticide application amounts and dates, planting dates, planting quantity and crop variety, and harvest dates. This data set represents the only known long‐term set of data characterizing food production and sustainability in irrigated and rainfed Mediterranean annual cropping systems. There are no copyright restrictions associated with the use of this dataset.
Kristina M. Wolf; Emma E. Torbert; Dennis Bryant; Martin Burger; R. Ford Denison; Israel Herrera; Jan Hopmans; Will Horwath; Stephen Kaffka; Angela Y. Y. Kong; R. F. Norris; Johan Six; Thomas P. Tomich; Kate M. Scow. The century experiment: the first twenty years of UC Davis' Mediterranean agroecological experiment. Ecology 2018, 99, 503 -503.
AMA StyleKristina M. Wolf, Emma E. Torbert, Dennis Bryant, Martin Burger, R. Ford Denison, Israel Herrera, Jan Hopmans, Will Horwath, Stephen Kaffka, Angela Y. Y. Kong, R. F. Norris, Johan Six, Thomas P. Tomich, Kate M. Scow. The century experiment: the first twenty years of UC Davis' Mediterranean agroecological experiment. Ecology. 2018; 99 (2):503-503.
Chicago/Turabian StyleKristina M. Wolf; Emma E. Torbert; Dennis Bryant; Martin Burger; R. Ford Denison; Israel Herrera; Jan Hopmans; Will Horwath; Stephen Kaffka; Angela Y. Y. Kong; R. F. Norris; Johan Six; Thomas P. Tomich; Kate M. Scow. 2018. "The century experiment: the first twenty years of UC Davis' Mediterranean agroecological experiment." Ecology 99, no. 2: 503-503.
Mountain runoff ultimately reflects the difference between precipitation (P) and evapotranspiration (ET), as modulated by biogeophysical mechanisms that intensify or alleviate drought impacts. These modulating mechanisms are seldom measured and not fully understood. The impact of the warm 2012–15 California drought on the heavily instrumented Kings River basin provides an extraordinary opportunity to enumerate four mechanisms that controlled the impact of drought on mountain hydrology. Two mechanisms intensified the impact: (i) evaporative processes have first access to local precipitation, which decreased the fractional allocation of P to runoff in 2012–15 and reduced P-ET by 30% relative to previous years, and (ii) 2012–15 was 1 °C warmer than the previous decade, which increased ET relative to previous years and reduced P-ET by 5%. The other two mechanisms alleviated the impact: (iii) spatial heterogeneity and the continuing supply of runoff from higher elevations increased 2012–15 P-ET by 10% relative to that expected for a homogenous basin, and iv) drought-associated dieback and wildfire thinned the forest and decreased ET, which increased 2016 P-ET by 15%. These mechanisms are all important and may offset each other; analyses that neglect one or more will over or underestimate the impact of drought and warming on mountain runoff.
Roger C. Bales; Michael L. Goulden; Carolyn T. Hunsaker; Martha H. Conklin; Peter C. Hartsough; Anthony T. O’Geen; Jan Hopmans; Mohammad Safeeq. Mechanisms controlling the impact of multi-year drought on mountain hydrology. Scientific Reports 2018, 8, 1 -8.
AMA StyleRoger C. Bales, Michael L. Goulden, Carolyn T. Hunsaker, Martha H. Conklin, Peter C. Hartsough, Anthony T. O’Geen, Jan Hopmans, Mohammad Safeeq. Mechanisms controlling the impact of multi-year drought on mountain hydrology. Scientific Reports. 2018; 8 (1):1-8.
Chicago/Turabian StyleRoger C. Bales; Michael L. Goulden; Carolyn T. Hunsaker; Martha H. Conklin; Peter C. Hartsough; Anthony T. O’Geen; Jan Hopmans; Mohammad Safeeq. 2018. "Mechanisms controlling the impact of multi-year drought on mountain hydrology." Scientific Reports 8, no. 1: 1-8.
Daniela Jerszurki; Valentin Couvreur; Toby Maxwell; Lucas Silva; Nicholas Matsumoto; Kenneth Shackel; Jorge Luiz Moretti de Souza; Jan Hopmans. Impact of root growth and hydraulic conductance on canopy carbon-water relations of young walnut trees ( Juglans regia L.) under drought. Scientia Horticulturae 2017, 226, 342 -352.
AMA StyleDaniela Jerszurki, Valentin Couvreur, Toby Maxwell, Lucas Silva, Nicholas Matsumoto, Kenneth Shackel, Jorge Luiz Moretti de Souza, Jan Hopmans. Impact of root growth and hydraulic conductance on canopy carbon-water relations of young walnut trees ( Juglans regia L.) under drought. Scientia Horticulturae. 2017; 226 ():342-352.
Chicago/Turabian StyleDaniela Jerszurki; Valentin Couvreur; Toby Maxwell; Lucas Silva; Nicholas Matsumoto; Kenneth Shackel; Jorge Luiz Moretti de Souza; Jan Hopmans. 2017. "Impact of root growth and hydraulic conductance on canopy carbon-water relations of young walnut trees ( Juglans regia L.) under drought." Scientia Horticulturae 226, no. : 342-352.
California growers face challenges with water shortages and there is a strong need to use the least amount of water while optimizing yield. Timely information on evapotranspiration (ET), a dominant component of crop consumptive water use, is critical for growers to tailor irrigation management based on in-field spatial variability and in-season variations. We evaluated the performance of a remote sensing-based approach, Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC), in mapping ET over an almond orchard in California, driven by Landsat satellite observations. Reference ET from a network of weather stations over well-watered grass (ETo) was used for the internal calibration and for deriving ET at daily and extended time period, instead of alfalfa based reference evapotranspiration (ETr). Our study showed that METRIC daily ET estimates during Landsat overpass dates agreed well with the field measurements. During 2009–2012, a root mean square error (RMSE) of 0.53 mm/day and a coefficient of determination (R2) of 0.87 were found between METRIC versus observed daily ET. Monthly ET estimates had a higher accuracy, with a RMSE of 12.08 mm/month, a R2 of 0.90, and a relatively small relative mean difference (RMD) of 9.68% during 2009–2012 growing seasons. Net radiation and Normalized Difference Vegetation Index (NDVI) from remote sensing observations were highly correlated with spatial and temporal ET estimates. An empirical model was developed to estimate daily ET using NDVI, net radiation (Rn), and vapor pressure deficit (VPD). The validation showed that the accuracy of this easy-to-use empirical method was slightly lower than that of METRIC but still reasonable, with a RMSE of 0.71 mm/day when compared to ground measurements. The remote sensing based ET estimate will support a variety of State and local interests in water use and irrigation management, for both planning and regulatory/compliance purposes, and it provides the farmers observation-based guidance for site-specific and time-sensitive irrigation management.
Ruyan He; Yufang Jin; Maziar M. Kandelous; Daniele Zaccaria; Blake L. Sanden; Richard L. Snyder; Jinbao Jiang; Jan W. Hopmans. Evapotranspiration Estimate over an Almond Orchard Using Landsat Satellite Observations. Remote Sensing 2017, 9, 436 .
AMA StyleRuyan He, Yufang Jin, Maziar M. Kandelous, Daniele Zaccaria, Blake L. Sanden, Richard L. Snyder, Jinbao Jiang, Jan W. Hopmans. Evapotranspiration Estimate over an Almond Orchard Using Landsat Satellite Observations. Remote Sensing. 2017; 9 (5):436.
Chicago/Turabian StyleRuyan He; Yufang Jin; Maziar M. Kandelous; Daniele Zaccaria; Blake L. Sanden; Richard L. Snyder; Jinbao Jiang; Jan W. Hopmans. 2017. "Evapotranspiration Estimate over an Almond Orchard Using Landsat Satellite Observations." Remote Sensing 9, no. 5: 436.
Michael W. Wolff; Jan W. Hopmans; Christine M. Stockert; Martin Burger; Blake L. Sanden; David R. Smart. Effects of drip fertigation frequency and N-source on soil N2O production in almonds. Agriculture, Ecosystems & Environment 2017, 238, 67 -77.
AMA StyleMichael W. Wolff, Jan W. Hopmans, Christine M. Stockert, Martin Burger, Blake L. Sanden, David R. Smart. Effects of drip fertigation frequency and N-source on soil N2O production in almonds. Agriculture, Ecosystems & Environment. 2017; 238 ():67-77.
Chicago/Turabian StyleMichael W. Wolff; Jan W. Hopmans; Christine M. Stockert; Martin Burger; Blake L. Sanden; David R. Smart. 2017. "Effects of drip fertigation frequency and N-source on soil N2O production in almonds." Agriculture, Ecosystems & Environment 238, no. : 67-77.
Large spatial and temporal variability in water flow and N transport dynamics poses significant challenges to accurately estimating N losses form orchards. A 2-yr study was conducted to explore nitrate (NO3−) leaching below the root zone of an almond [Prunus dulcis (Mill.) D. A. Webb] orchard. Temporal changes in water content, pore water NO3− concentrations and soil water potential were monitored within and below the root zone to a soil depth of 3 m at eight sites, which represented spatial variations in soil profiles within an almond orchard in California. Orchard monthly average NO3− concentrations below the root zone ranged from 225 to 710 mg L−1 with mean annual concentration of 468 and 333 mg L−1 for the 2014 and 2015 growing seasons, respectively. Despite the huge variability in pore water NO3− concentration between sites, the larger spatiotemporal scale N losses estimated at the annual orchard scale from surface N mass balance, vadose zone based water and N mass balance, flow calculations, and HYDRUS modeling were all on the same order of magnitude (80–240 kg N ha−1 yr−1). All methods indicated that most of the N losses occur early in the growing season (February–May) when fertilizer is applied to wet soil profiles. Simple mass balance (i.e., N load applied minus N load removed) provided a good proxy of the annual N accumulation in the soil profile at the orchard scale. Reduction of N losses at the orchard scale would require alternative fertigation and irrigation practices to decrease the difference between the N load removed and the N load applied to orchards. Copyright © 2016. . Copyright © by the Soil Science Society of America, Inc.
S. Baram; Valentin Couvreur; T. Harter; M. Read; Patrick Brown; Maziar Kandelous; D.R. Smart; Jan Hopmans. Estimating Nitrate Leaching to Groundwater from Orchards: Comparing Crop Nitrogen Excess, Deep Vadose Zone Data‐Driven Estimates, and HYDRUS Modeling. Vadose Zone Journal 2016, 15, 1 -13.
AMA StyleS. Baram, Valentin Couvreur, T. Harter, M. Read, Patrick Brown, Maziar Kandelous, D.R. Smart, Jan Hopmans. Estimating Nitrate Leaching to Groundwater from Orchards: Comparing Crop Nitrogen Excess, Deep Vadose Zone Data‐Driven Estimates, and HYDRUS Modeling. Vadose Zone Journal. 2016; 15 (11):1-13.
Chicago/Turabian StyleS. Baram; Valentin Couvreur; T. Harter; M. Read; Patrick Brown; Maziar Kandelous; D.R. Smart; Jan Hopmans. 2016. "Estimating Nitrate Leaching to Groundwater from Orchards: Comparing Crop Nitrogen Excess, Deep Vadose Zone Data‐Driven Estimates, and HYDRUS Modeling." Vadose Zone Journal 15, no. 11: 1-13.
A 2-year study was conducted to explore the impact of current and alternative best management practices (BMPs) of irrigation and fertigation on nitrate (NO3−) leaching below the root zone. Using a fully randomized complete block design, three fertigation strategies were compared: current BMP with and without accounting for NO3−-N in irrigation-water, and a high frequency fertigation treatment with low-N concentration applications. Temporal changes in water content, pore water NO3− concentrations and soil water potential were monitored within and below the root zone to a soil depth of 3 m at eight sites in an almond and a pistachio orchard. NO3− concentrations below the root zone ranged from <1 mg L−1 to more than 2400 mg L−1 (almond), and up to 11,000 (pistachio) mg L−1, with mean concentrations of 326 and 4631 mg L−1, respectively. Within the fertigation cycle, fertilizer injection at the end of an irrigation event generally resulted in lower NO3− losses below the root zone compared with fertilizer injection midway through the irrigation. Pre-bloom and post-harvest flood irrigation in the almond orchard caused deep soil wetting and flushing of NO3− below the root zone, threatening groundwater quality. Statistical analysis using principal component analysis, Chi-squared Automatic Interaction Detector and the Artificial Neural Network showed that most of the deep soil NO3− concentration variability could not be explained by irrigation duration, fertigation timing or local variations in soil physical characteristics. However, mass balance estimates for water and N indicated the annual orchard average N loss could be estimated based on eight monitoring sites in spite of the inherent spatial variations in soil properties and the spatiotemporal variations in water and NO3− applications. The study indicated that reduction of N losses at the orchard scale would require alternative fertigation and irrigation practices, including better control of fertigation amounts and irrigation duration.
S. Baram; Valentin Couvreur; Thomas Harter; Matthew Read; Patrick Brown; Jan Hopmans; D.R. Smart. Assessment of orchard N losses to groundwater with a vadose zone monitoring network. Agricultural Water Management 2016, 172, 83 -95.
AMA StyleS. Baram, Valentin Couvreur, Thomas Harter, Matthew Read, Patrick Brown, Jan Hopmans, D.R. Smart. Assessment of orchard N losses to groundwater with a vadose zone monitoring network. Agricultural Water Management. 2016; 172 ():83-95.
Chicago/Turabian StyleS. Baram; Valentin Couvreur; Thomas Harter; Matthew Read; Patrick Brown; Jan Hopmans; D.R. Smart. 2016. "Assessment of orchard N losses to groundwater with a vadose zone monitoring network." Agricultural Water Management 172, no. : 83-95.
The remarkable complexity of soil and its importance to a wide range of ecosystem services presents major challenges to the modeling of soil processes. Although major progress in soil models has occurred in the last decades, models of soil processes remain disjointed between disciplines or ecosystem services, with considerable uncertainty remaining in the quality of predictions and several challenges that remain yet to be addressed. First, there is a need to improve exchange of knowledge and experience among the different disciplines in soil science and to reach out to other Earth science communities. Second, the community needs to develop a new generation of soil models based on a systemic approach comprising relevant physical, chemical, and biological processes to address critical knowledge gaps in our understanding of soil processes and their interactions. Overcoming these challenges will facilitate exchanges between soil modeling and climate, plant, and social science modeling communities. It will allow us to contribute to preserve and improve our assessment of ecosystem services and advance our understanding of climate-change feedback mechanisms, among others, thereby facilitating and strengthening communication among scientific disciplines and society. We review the role of modeling soil processes in quantifying key soil processes that shape ecosystem services, with a focus on provisioning and regulating services. We then identify key challenges in modeling soil processes, including the systematic incorporation of heterogeneity and uncertainty, the integration of data and models, and strategies for effective integration of knowledge on physical, chemical, and biological soil processes. We discuss how the soil modeling community could best interface with modern modeling activities in other disciplines, such as climate, ecology, and plant research, and how to weave novel observation and measurement techniques into soil models. We propose the establishment of an international soil modeling consortium to coherently advance soil modeling activities and foster communication with other Earth science disciplines. Such a consortium should promote soil modeling platforms and data repository for model development, calibration and intercomparison essential for addressing contemporary challenges. Copyright © 2016. . Copyright © by the Soil Science Society of America, Inc.
H. Vereecken; Andrea Schnepf; Jan Hopmans; Mathieu Javaux; Dani Or; Tiina Roose; Jan Vanderborght; M.H. Young; W. Amelung; M. Aitkenhead; S.D. Allison; S. Assouline; Philippe Baveye; M. Berli; Nicolas Brüggemann; Peter Finke; Markus Flury; T. Gaiser; G. Govers; Teamrat Ghezzehei; Paul Hallett; H.J. Hendricks Franssen; J. Heppell; R. Horn; Johan Alexander Huisman; Diederik Jacques; F. Jonard; Stefan Kollet; F. Lafolie; Krzysztof Lamorski; D. Leitner; Alex McBratney; Budiman Minasny; Carsten Montzka; Wolfgang Nowak; Y. Pachepsky; J. Padarian; Nunzio Romano; K. Roth; Youri Rothfuss; Ed Rowe; A. Schwen; J. Šimůnek; Aaldrik Tiktak; J. Van Dam; S.E.A.T.M. Van Der Zee; Hans-Jörg Vogel; J.A. Vrugt; Thomas Wöhling; I.M. Young. Modeling Soil Processes: Review, Key Challenges, and New Perspectives. Vadose Zone Journal 2016, 15, 1 .
AMA StyleH. Vereecken, Andrea Schnepf, Jan Hopmans, Mathieu Javaux, Dani Or, Tiina Roose, Jan Vanderborght, M.H. Young, W. Amelung, M. Aitkenhead, S.D. Allison, S. Assouline, Philippe Baveye, M. Berli, Nicolas Brüggemann, Peter Finke, Markus Flury, T. Gaiser, G. Govers, Teamrat Ghezzehei, Paul Hallett, H.J. Hendricks Franssen, J. Heppell, R. Horn, Johan Alexander Huisman, Diederik Jacques, F. Jonard, Stefan Kollet, F. Lafolie, Krzysztof Lamorski, D. Leitner, Alex McBratney, Budiman Minasny, Carsten Montzka, Wolfgang Nowak, Y. Pachepsky, J. Padarian, Nunzio Romano, K. Roth, Youri Rothfuss, Ed Rowe, A. Schwen, J. Šimůnek, Aaldrik Tiktak, J. Van Dam, S.E.A.T.M. Van Der Zee, Hans-Jörg Vogel, J.A. Vrugt, Thomas Wöhling, I.M. Young. Modeling Soil Processes: Review, Key Challenges, and New Perspectives. Vadose Zone Journal. 2016; 15 (5):1.
Chicago/Turabian StyleH. Vereecken; Andrea Schnepf; Jan Hopmans; Mathieu Javaux; Dani Or; Tiina Roose; Jan Vanderborght; M.H. Young; W. Amelung; M. Aitkenhead; S.D. Allison; S. Assouline; Philippe Baveye; M. Berli; Nicolas Brüggemann; Peter Finke; Markus Flury; T. Gaiser; G. Govers; Teamrat Ghezzehei; Paul Hallett; H.J. Hendricks Franssen; J. Heppell; R. Horn; Johan Alexander Huisman; Diederik Jacques; F. Jonard; Stefan Kollet; F. Lafolie; Krzysztof Lamorski; D. Leitner; Alex McBratney; Budiman Minasny; Carsten Montzka; Wolfgang Nowak; Y. Pachepsky; J. Padarian; Nunzio Romano; K. Roth; Youri Rothfuss; Ed Rowe; A. Schwen; J. Šimůnek; Aaldrik Tiktak; J. Van Dam; S.E.A.T.M. Van Der Zee; Hans-Jörg Vogel; J.A. Vrugt; Thomas Wöhling; I.M. Young. 2016. "Modeling Soil Processes: Review, Key Challenges, and New Perspectives." Vadose Zone Journal 15, no. 5: 1.
Accurate modeling of water and air flow in porous media requires the definition of the relevant hydraulic properties, namely, the water retention curve (WRC) and the relative hydraulic conductivity function (RHC), as well as the definition of the relative air permeability function (RAP). Capitalizing on the approach developed previously to represent the RHC (Assouline, 2001), a new model allowing the prediction of RAP based on information resulting from the WRC is proposed. The power value ηa in the model is a decreasing exponential function of the coefficient of variation, ε, characterizing the pore size distribution of the porous medium, and stemming from its WRC. The model was calibrated using data from 22 disturbed and undisturbed soil samples and was validated using data from 6 soil samples ranging from sand to silty clay loam. The proposed model provided accurate prediction of the soil RAP and performed in some cases (sandy loam and silty clay loam soils) better than available alternative models. This article is protected by copyright. All rights reserved.
S. Assouline; A. Tuli; Jan Hopmans. Evaluating the relative air permeability of porous media from their water retention curves. Water Resources Research 2016, 52, 3428 -3439.
AMA StyleS. Assouline, A. Tuli, Jan Hopmans. Evaluating the relative air permeability of porous media from their water retention curves. Water Resources Research. 2016; 52 (5):3428-3439.
Chicago/Turabian StyleS. Assouline; A. Tuli; Jan Hopmans. 2016. "Evaluating the relative air permeability of porous media from their water retention curves." Water Resources Research 52, no. 5: 3428-3439.
Estimation of field spatial variability of tree actual evapotranspiration (ETa) in orchards is key when quantifying water and associated nutrient leaching at the field scale. Though ETa is often measured at the field scale, spatial variations between individual trees are likely due to local differences in soil water availability and canopy cover. It is therefore that we propose seeking a statistical relation between field ETa, tree midday stem water potential (MSWP), soil water storage (WS), and tree potential evapotranspiration (ETc) with relative tree canopy cover (Crel). Four years of soil and almond trees water status data were used to optimize an artificial neural network (ANN), to predict field scale ETa first, followed by downscaling to the individual tree scale. ANN's using two hidden neurons (11 parameters) proved to be the most accurate (RMSE = 0.0246 mm/h, R2 = 0.944), seemingly because adding more neurons generated overfitting of noise in the training dataset. Crel was the main source of variability of ETa, while MSWP was the controlling factor for the tree-scale relative ET. At a given soil WS, almond trees of the drip-irrigated block were less affected by root zone water stress than the fanjet micro-sprinklers block, likely because of soil textural differences between the two main experimental blocks. In wet conditions, the predicted tree ETa followed a normal distribution (with relative standard deviation of about 5%), which was close to the Crel distribution. However, standard deviation values increased (7.6% for the whole orchard) during periods of water stress.
Valentin Couvreur; M.M. Kandelous; B.L. Sanden; B.D. Lampinen; Jan Hopmans. Downscaling transpiration rate from field to tree scale. Agricultural and Forest Meteorology 2016, 221, 71 -77.
AMA StyleValentin Couvreur, M.M. Kandelous, B.L. Sanden, B.D. Lampinen, Jan Hopmans. Downscaling transpiration rate from field to tree scale. Agricultural and Forest Meteorology. 2016; 221 ():71-77.
Chicago/Turabian StyleValentin Couvreur; M.M. Kandelous; B.L. Sanden; B.D. Lampinen; Jan Hopmans. 2016. "Downscaling transpiration rate from field to tree scale." Agricultural and Forest Meteorology 221, no. : 71-77.
Highlights•Identifies most time stable location (MTSL) and depth (MTSD) for study area soil water content (SWC).•Just one time-stable location sufficed to estimate the mean SWC of the study area.•Additional MTSLs were required to estimate the area’s mean SWC based on the MTSD.•Identified MTSL’s and MTSD’s could be upscaled for SWC estimates at the watershed scale. SummaryTo minimize the number of soil water content (SWC) measurements for estimation of field- or watershed-scale soil water storage, we present an analysis of time-stable soil water data across both measurement locations and soil depth intervals. The proposed analysis applies the time stability concept to select area-representative measurement locations, and assesses the potential for identifying the most time-stable depth interval (MTSD) using a minimal number of selected time-stable locations (MTSLs). For that purpose, we used a time series of 21 SWC datasets, measured at 20 locations and 20 corresponding depth intervals down a 3-m soil profile, during a two-year period in the 38-ha study area of the Liudaogou watershed of the China Loess Plateau. After identifying the MTSLs, analysis of time stability of measurement depth intervals showed single soil water depth measurements at between 2 and 5 of the MTSLs were sufficient to determine the area-representative SWC. The MTSD was determined to be about mid-way in the soil profile, irrespective of total soil profile depth measured. Confirmation of the time-stability analyses was done by comparing the representative SWC estimations for the 38-ha sampling area with additional SWC measurements across the 6.9 km2 watershed. The encouraging results of our analysis suggest that time stability analysis may be an effective way to assess large-scale soil water storage in arid and semi-arid regions.
Dongli She; Wenjuan Zhang; Jan Hopmans; Luís Carlos Timm. Area representative soil water content estimations from limited measurements at time-stable locations or depths. Journal of Hydrology 2015, 530, 580 -590.
AMA StyleDongli She, Wenjuan Zhang, Jan Hopmans, Luís Carlos Timm. Area representative soil water content estimations from limited measurements at time-stable locations or depths. Journal of Hydrology. 2015; 530 ():580-590.
Chicago/Turabian StyleDongli She; Wenjuan Zhang; Jan Hopmans; Luís Carlos Timm. 2015. "Area representative soil water content estimations from limited measurements at time-stable locations or depths." Journal of Hydrology 530, no. : 580-590.
Maziar M. Kandelous; Barzin A. Moradi; Jan Hopmans. An Alternative Tensiometer Design for Deep Vadose Zone Monitoring. Soil Science Society of America Journal 2015, 79, 1293 -1296.
AMA StyleMaziar M. Kandelous, Barzin A. Moradi, Jan Hopmans. An Alternative Tensiometer Design for Deep Vadose Zone Monitoring. Soil Science Society of America Journal. 2015; 79 (5):1293-1296.
Chicago/Turabian StyleMaziar M. Kandelous; Barzin A. Moradi; Jan Hopmans. 2015. "An Alternative Tensiometer Design for Deep Vadose Zone Monitoring." Soil Science Society of America Journal 79, no. 5: 1293-1296.
The dual-probe heat-pulse (DPHP) method is attractive for measuring soil thermal properties and volumetric water content. The purpose of this study was to develop and test a DPHP sensor having rigid probes made from thick-walled stainless steel tubing (2.38-mm outside diameter). The probes of this sensor are much more resistant to deflection than those of conventional DPHP sensors, decreasing measurement error caused by probe deflection during insertion into the soil. Laboratory experiments were conducted across a wide range of saturation levels with glass beads and three soils of different textures. For inferring soil properties from the proposed sensor, we applied the recently developed identical cylindrical perfect conductors (ICPC) model instead of the infinite line source (ILS) model that is typically used. The ICPC model improves solution for heat transport through the probe–soil system by accounting for the heat capacity and radius of the probes. Our results show a root mean square error of 1.4% volumetric water content and elimination of the measurement bias typically encountered with DPHP measurements. We conclude that the improved sensor, in combination with the ICPC model, provides a general, soil-independent water content estimate that is especially suitable for field soil water content monitoring because of its robust design with rigid probes. Because of its simplicity and measurements independent of soil type, we propose the presented DPHP method as an excellent alternative to other available measurement techniques for soil water content. Copyright © 2015. . Copyright © by the Soil Science Society of America, Inc.
Tamir Kamai; Gerard J. Kluitenberg; Jan W. Hopmans. A Dual‐Probe Heat‐Pulse Sensor with Rigid Probes for Improved Soil Water Content Measurement. Soil Science Society of America Journal 2015, 79, 1059 -1072.
AMA StyleTamir Kamai, Gerard J. Kluitenberg, Jan W. Hopmans. A Dual‐Probe Heat‐Pulse Sensor with Rigid Probes for Improved Soil Water Content Measurement. Soil Science Society of America Journal. 2015; 79 (4):1059-1072.
Chicago/Turabian StyleTamir Kamai; Gerard J. Kluitenberg; Jan W. Hopmans. 2015. "A Dual‐Probe Heat‐Pulse Sensor with Rigid Probes for Improved Soil Water Content Measurement." Soil Science Society of America Journal 79, no. 4: 1059-1072.