To enable an efficient and economical use of limited water resources, sensing techniques to determine root zone soil moisture are gaining importance. Because of their easy handling and ability to provide simultaneous measurements in different depths, so-called soil moisture profile sensors (SMPS) exhibit high potential for climate-smart agriculture. However, determining soil moisture with reasonable accuracy is a complex task. Especially clay content and soil temperature influence the soil dielectric permittivity and might thus affect the electromagnetic soil moisture measurement of the SMPS.

To date, an accurate and easy-to-use method for the evaluation of long SMPS is not available. To this end, we designed a laboratory and a field experiment to better discriminate between changes in soil dielectric permittivity and sensor variability due to environmental effects. The tested SMPS are the SoilVUE10 (50 cm) from Campbell Scientific, the Drill&Drop (60 cm) from Sentek, as well as the SMT500 (50 cm), which is an early prototype from TRUEBNER. The following questions were addressed: (1) How high is the measurement variability of the vertical measurement sections of an SMPS? (2) How strong is the sensor response influenced by changes in temperature? (3) What is the SMPS accuracy compared to reference TDR measurements and how high is the sensor-to-sensor variability? We addressed questions 1 and 2 by placing the SMPS into a container filled with well-characterized fine to medium sized sand (type F36, Quarzwerke Frechen). The sand was water saturated and the temperature of the container was stepwise increased from 5 to 40 °C using a water cooling/heating. Question 3 was addressed by setting up a 2 x 2 x 1.5 m sandbox, also filled with F36 sand at a field site. The sandbox is sealed watertight to the sides and to the bottom and provided with a drainage layer of 20 cm gravel. The water level inside the sandbox can be controlled by pumping water in or out using piezometer tubes, which are permeable in the drainage layer. The SMPS were installed into the sandbox and the measurements were compared against reference measurements made using CS610 TDR probes with TDR100 (Campbell Scientific) and against SMT100 (TRUEBNER) TDT measurements.

Preliminary results using factory calibrations indicate that all tested SMPS have their shortcomings regarding the accuracy of soil moisture estimation. The D&D probe shows a high agreement between the measurement depths and a fair temperature stability, but the soil moisture content was underestimated compared to the reference measurements. In comparison, the SoilVUE10 displayed larger variability between different measurement depths, as well as between different sensors. In addition, the soil moisture was overestimated at high soil moisture content and the accuracy declined strongly above a soil temperature of 25°C. The SMT500, albeit a prototype, performed well at low soil moisture but strongly overestimated the soil water content under saturated conditions. Our experimental setup has generally proven useful for the characterization of SMPS. It clearly showed that the accuracy of the soil moisture estimates obtained with the SMPS is quite variable, especially at high soil moisture content.

How to cite: Nieberding, F., Huisman, J. A., Huebner, C., Weuthen, A., Schilling, B., and Bogena, H. R.: Playing in the sandbox: An experimental set-up for comparison of soil moisture profile sensors, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1098, https://doi.org/10.5194/egusphere-egu23-1098, 2023.

The main goal of this study was to determine the effect of surface cover on soil percolation. Many previous papers have focused on reducing soil loss on steep slopes using geotextiles, but not on the intensity of percolation. Reducing surface runoff can help reduce soil loss, but increased infiltration can also increase the risk of slope collapse. For this research, Enkamat 7220 (plastic geotextile) in six different cover variations was used, as well as bare soil for comparison. A laboratory rainfall simulator with variable rainfall intensity and adjustable slope was used for the experiments, which were conducted at rainfall intensities of 60-160 mm/h. The results showed that the lowest soil percolation occurred on the plot with bare soil and on the plot where the entire surface was covered with geotextile and fully backfilled, likely due to soil compaction. The highest percolation was observed on the plot where the geotextile was fixed on top of the surface using ground anchors. The hypothesis that percolation at the foot of the slope is higher than at the top of the slope due to surface and subsurface flow was also confirmed. In future studies on the effectiveness of geotextiles, additional measurements of percolation would be beneficial for a deeper understanding of these processes. This research was supported by the research projects QK22010261, SS05010180 and CTU in Prague, grant No. SGS OHK1-086/23/11143.

How to cite: Neumann, M., Kavka, P., Tejkl, A., Laburda, T., and Beck-Broichsitter, S.: Influence of soil cover on surface runoff, infiltration, and percolation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5351, https://doi.org/10.5194/egusphere-egu23-5351, 2023.

Time-lapse photogrammetry has been proven to be a valuable tool to support the understanding of earth surface processes since it can be used to create 3D models with an unprecedented temporal resolution. Overlapping images are captured simultaneously and structure from motion (SfM) photogrammetry is used to reconstruct 3D point clouds from these images automatically.

We performed one rainfall simulation on an erosion plot in the field covering about 16 square meters and having a slope of 9 degrees and another experiment in the laboratory with a plot of about 4 square meters and a slope of 20 degrees. Rainfall intensities were similar and high in both simulations to ensure rill formation. During the experiment, we measured soil surface changes with a time series of 3D point clouds derived via SfM photogrammetry. We also estimated runoff flow velocities with a tracer and observed the spatial pattern of runoff velocities with particle tracking velocimetry (PTV) applied to videos captured during the field experiment. At the plot outlet, we also measured runoff and sediment yield. These datasets were used as validation data for the soil erosion model.

Soil erosion was simulated with the physically-based model RillGrow and SMODERP, which conceptualizes the formation of erosion rills as a self-organizing dynamic system. We ran several thousand erosion simulations using a Monte Carlo approach. The aim was first to assess the sensitivity of the input parameters of the model, and secondly to automatically find the best fitting set of input parameter values for the given field site conditions and rainfall intensity. We compare the simulation results to global values, such as the sediment yield and runoff, and to local changes, measured by the photogrammetric 4D data.

Our study combines established as well as newly developed data recording and processing methods to create a spatio-temporal high-resolution dataset. This is used to test a soil erosion model with the aim of enhancing understanding of rill erosion processes.

This research was supported by the projects DFG EL926/3-1, SFZP 085320/2022, SS05010180, and SGS OHK1-086/23/11143.

How to cite: Grothum, O., Favis-Mortlock, D., Kavka, P., Neumann, M., Laburda, T., and Eltner, A.: Spatio-temporally highly resolved validation of a rill-based soil erosion model with 4D data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6524, https://doi.org/10.5194/egusphere-egu23-6524, 2023.

This contribution presented cartographic visualization of project aims.  The goal is to presented the classification the potential utility of irrigation and available water in the Czech Republic territory in the scale of small catchment in square km size. Definition and basic classification of the are presented by Kavka (Kavka, 2021). Classification of the these catchments based on various factors such as terrain morphology, soil characteristics, drought risk, and rainfall variability with final. Main goal of presented are involves the assessing options for retention of the water in the agriculture landscape for the consequence irrigation systems. The research are also focused to the designing and implementing a system for monitoring soil water regimes in irrigated areas as a tool for optimizing irrigation systems and managing water resources.

Water resources are limited by the amount of rainfall and the ways to capture water from extreme precipitation events. To make the most efficient use of these resources, it is important to capture water directly in source catchments and use it for irrigation, rather than relying on technology-intensive infrastructure. Given the changes in climate, which in temperate Central Europe can bring about higher concentrations of extreme precipitation and longer dry periods, it is crucial to adaptation for future changes. From an agricultural perspective, changes in the rapid component of runoff and reduced retention capacity are also key considerations.

In areas that are not near significant watercourses with constant and relative high flow, local sources of water for irrigation may not be relevant. The project includes the identification of areas where it may be possible to store irrigation water at a local scale. The evaluation of the need for hydrological models, local measurements, and balance characteristics of the area. This involves determining the water needs in small catchments, primarily targeted at local irrigation systems, and researching sources of moisture needs. Data on existing and historical small reservoirs and areas with potential water storage for irrigation needs in the source catchments are used for these analyses, considering existing agro-climatic areas and identified historical irrigation systems. The areas with low or zero infiltration (paved road, cities, buildings, etc.) are identified.

 Acknowledgements: This contribution was supported by grant of the The Technology Agency of the Czech Republic – No. SS01020052 - “Utility and risk of irrigation over the Czech Republic in changing climate”. 

How to cite: Kavka, P., Neumann, M., Tejkl, A., Kuráž, M., and Hanel, M.: The Influence of Climate Change on Runoff from Headwater Catchments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8277, https://doi.org/10.5194/egusphere-egu23-8277, 2023.

Ammonia volatilization (AV) is one of the main pathways of nitrogen fertilizer loss, resulting in reduced crop yields, and a negative impact on the environment. Therefore, reducing AV through proper fertilizer management is essential. We can, however, only provide appropriate management advice when based on accurate measurements, along with understanding the processes involved. For this purpose, the ¹⁵N technique has a unique advantage over other methods to precisely identify the sources of ammonia production.

A field experiment was established at the SWMCN laboratory in Seibersdorf on maize with four replications and 120 kg N ha^-1 was applied through two equal split applications at 20 DAP (Days After Planting) and 34 DAP. Two ¹⁵N microplots inside each main plot were installed. In these microplots, ¹⁵N-labeled urea replaced the unlabeled urea according to the time of fertilizer application. Each microplot for ¹⁵N-labelled urea was 2.5 m by 2.5 m,and the buffer zone between microplots was 1 m to minimize ¹⁵N contamination from adjacent microplot. For these microplots, ¹⁵N-labeled urea was used with an enrichment of 5.23 atom% ¹⁵N excess. The first microplot received ¹⁵N-urea at 20 DAP and unlabeled urea at 34 DAP, the second microplot received ¹⁵N-urea at 34 DAP and unlabeled urea at 20 DAP. Ammonia volatilization was measured with semi-static chambers and chambers were installed inside the ¹⁵N microplots.

The total cumulative NH₃ emissions from urea after the first and second split applications were 13.9 kg N ha^-1 and 18.0 kg N ha^-1, respectively. This calculation is based on the difference in AV between experimental treatments and control treatment, assuming that AV in control plots indicates the amount of AV from the soil source, whereas AV of the fertilized treatments presents AV from soil and fertilizer sources. It also assumes that all nitrogen transformations, i.e., mineralization, immobilization, and other process in the case of nitrogen, are the same for control and experimental plots. Therefore, the amount of AV in urea treatment was subtracted from the amount of AV in control treatment. The cumulative NH₃ emissions from the control treatment (without nitrogen fertilizer) at the same time were 2.7 kg N ha^-1 and 3.6 kg N ha^-1, respectively. Accordingly, about 20% of the ammonia volatilized from the soil source and the rest could be attributed to the added urea fertilizer.

However, using the ¹⁵N labelled fertilizer, it was found that the above assumption shows some flaws. The fraction of nitrogen in the ammonia samples derived from the soil is not constant but changes significantly due to nitrogen fertilizer application. The results show that the nitrogen in the ammonia derived from the fertilizer was 65% and 53% after the first and second split applications, respectively. Therefore, the fraction of nitrogen in the ammonia samples derived from the soil source was 35% and 47% after the first and second split applications. So, the use of the ¹⁵N technique shows that adding nitrogen fertilizer likely increased the rate of mineralization by changing the ratio of carbon to nitrogen.

How to cite: Heiling, M., Mirkhani, R., Resch, C., Pucher, R., Toloza, A., and Dercon, G.: Determining the contribution of nitrogen fertilizer and mineralization to volatilized ammonia through the use of nitrogen-15, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12071, https://doi.org/10.5194/egusphere-egu23-12071, 2023.

Abstract：The reservoir-bank collapse has caused soil erosion and bank expansion in the lower Yellow River, which seriously affects the ecological environment and agricultural development. Understanding the processes of mass movement occurred on reservoir-bank is important to predict and control bank expansion. However, little research exists concerning how to accurately quantify the process of bank collapse and trace the source of sediment. In this study, a reservoir-bank model with the gentle slope of 3°, steep slope of 40° and abrupt slope of 70°, was constructed according to geomorphological characteristics of the soil reservoir-bank in Xiaolangdi Reservoir, in which rare earth elements were used to trace the provenance of sediment originated from mass movement on reservoir-bank under different rainfall conditions, and quantify the soil loss from the bank contributed to sediment deposition in reservoir. The results show that the sediment in reservoir mainly comes from steep slope, and the percentage contribution of abrupt slope to the total soil loss increases significantly in rainstorms with the precipitation larger than 60 mm. Under the rainstorms, the contributions of the gentle slope, steep slope and abrupt slope to soil loss were 10%, 55% and 35%, respectively. Without rainstorm, the contributions of the gentle slope, steep slope, and abrupt slope to soil loss were 4%, 72% and 24%, respectively. Meanwhile, sediment deposition in reservoir also mainly derived from steep slope and abrupt slope. The contribution of steep slope and abrupt slope to sediment deposition were 49% and 40% under the rainstorms, and the contribution of steep slope and abrupt slope to sediment deposition without rainfall were 67% and 28%, respectively. In addition, most of the sediment generated from the lower abrupt slope accumulates near the reservoir-bank, while the sediment generated from the steep slope accumulates at a distance from the reservoir-bank. Under the rainstorms, the contribution of upper steep slope to sediment deposition was 54% at 240 cm from the reservoir-bank, while the contribution of lower steep slope to sediment deposition without rainfall was 70% at 180 cm from the reservoir-bank. Whether with or without rainfall, the contribution of lower abrupt slope to sediment deposition was all about 54% at 40 cm from the reservoir-bank. Thus, in the near future, engineering measures such as grid protected slope may be used in the reservoir area to protect the steep slope of reservoir-bank, which can effectively reduce soil erosion and bank expansion in the reservoir area.

Keywords: Bank collapse; Mass movement; Xiaolangdi Reservoir; REEs; Rainstorm

How to cite: Ran, G., Li, T., and Xu, X.: Quantifying provenance of soil originated from mass movement on soil reservoir-bank using rare earth elements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16172, https://doi.org/10.5194/egusphere-egu23-16172, 2023.

Soil is defined in different ways, depending on the scientific discipline and a project’s scope. Understanding these differences is key to facilitate clear communication of subsurface conditions within interdisciplinary project teams and allow a comprehensive presentation of results towards a broader audience. The goal of herein presented research is to find differences and analogies in discipline-dependent definitions of soil, outline resulting challenges and suggest possible solutions.

Definitions of the word soil were reviewed and analyzed in discipline-specific dictionaries of the Oxford reference dictionary series and international standards in regard to soil classifications (i. e. ISO and ASTM). Additionally, a survey was performed among professionals from different disciplines, including, but not limited to pedology, geology, engineering, geomorphology and chemistry. The survey aimed at finding out (i) how the word soil is defined by representatives of different disciplines, (ii) if there are divergent understandings between and within disciplines, (iii) if the various interpretations result in problems in interdisciplinary research and (iv) if and what kind of solutions are needed. The survey was filled out by sixty-two, mostly senior-level professionals from the private sector as well as universities and research institutions.

Together with the results of the analysis of dictionaries and international standards, the answers to the survey showed that there are recognizable differences in the understanding of the word soil and that the majority of the survey participants sees a need to find solutions to how these can be addressed, especially for interdisciplinary projects. It was found that consense among the project team and a clear and comprehensive definition of soil, as it is understood within in a specific project, is required as a minimum from the on-start of a project. Additionally, based on the results of the definitions given in literature as well as in the survey, typical definitions of soil are categorized according to discipline (e. g. soil science, geology, engineering) and a comprehensive summary of terminology and vocabulary is presented in regard to possible synonyms for the word soil. Both approaches aim to assist in defining the word soil by providing a simple terminological framework, in which the project’s detailed definition can be integrated. This framework is flexible enough to be extended to other relevant disciplines (e. g. agricultural science, forestry, law).

How to cite: Kurka, M.: What is Soil? – Addressing challenges due to interdisciplinary differences in the understanding of the word soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12277, https://doi.org/10.5194/egusphere-egu23-12277, 2023.