Search

A few low-frequent but extreme rainfall events generate substantial erosion amounts and, as a result, land degradation negatively affects soil health and agricultural productivity. Determining rainfall erosivity (from small to extreme events) that drive soil erosion will improve our knowledge and understanding of extreme erosion processes and our ability to develop and adapt adequate soil protection strategies. This study aims to analyze rainfall erosivity characteristics across Austria‘s main agricultural production zones using long-term (from 27 to 82 years) with high-resolution (5-minutes) rainfall data from 27 rain gauges. Erosive rainfall characteristics such as rainfall amount, event duration, and the maximum 30-minute intensity were investigated, and typical rainfall types were assessed through a clustering approach based on the k-means algorithm. Results identified three dominant types (clusters) of erosive rainfalls across Austria's agricultural areas. Seasonal distribution analysis showed that the predominant erosive events, characterized by short duration and high intensities, occur during the summer months from June to August. In contrast, the long-duration and low rainfall-intensity events are evenly distributed throughout the year. The spatial distribution of rainfalls related to the largest rainfall erosivities showed a pronounced occurrence in the southeastern pre-alpine areas. Knowledge of the occurrence of erosive rainfall events in space and time eventually supports the implementation of locally adapted Soil Conservation (SC) practices in Austria.

In our ACRP funded project EROS-A we aim at a comprehensive analysis of the erosive energy of rainfall, estimated soil loss, and reported damage using statistical and process-based methods. In this particular study, we evaluate the return periods of erosive rainfall events at 26 meteorological stations in Austria. The main focus is on daily cumulative rainfall and the maximum 30-min rainfall intensity (I30) as these were identified as key parameters for rainfall erosivity assessment. The extreme value series were obtained using both the Annual Maxima Series (AMS) and Peak Over Threshold (POT) approach, in order to assess which of the methods will be most accurate. The assumptions of stationarity and independence of the extreme value series were carefully checked using statistical trend and independence tests and no significant deviations were found.Generalized extreme value (GEV) and generalized Pareto (GPD) probability distributions were fitted using L-moment and maximum likelihood procedures. The GEV distribution is suited for AMS or block maxima data, whereas the GPD is suited for the POT series. For the obtained GEV and GPD models we examined extreme events with return periods of 2, 5, 10, 25, 50, and 100 years. We found that threshold selection is crucial for the POT, with diagnostic tools (such as mean residual life plots) not being fully decisive. Finally sensitivity analysis was performed where convergence of the fitted GPD to the GEV (AMS approach) helped determining robust thresholds for the GPD. The results show that the POT approach for daily cumulative precipitation is the most accurate in 69% of the cases and the AMS approach in 8% of the cases (different return periods and stations), while they have similar performance in 23% of the cases. Similar results are obtained for I30, were the success rates are 80% for the POT, 8% for the AMS and 12% for similar performance. In the next step, we will extend frequency analysis to a regional context, in order to map extreme rainfall erosivity across main agricultural production zones in Austria.

Five CMIP6 models were selected to project changes in rainfall erosivity of China for two future periods (the near-term in 2041-2065, the long-term in 2076-2100) under SSP1-RCP2.6 and SSP5-RCP8.5 scenarios. Models’ capacity in estimating two erosivity indices, annual average rainfall erosivity (R-factor) and the storm erosivity at 10-year return level (10-year storm EI) were evaluated by comparing the model derived indices for the historical period with the state-of-the-art reference erosivity maps of China interpolated with hourly observations. Results show that GFDL-ESM4, IPSL-CM6A-LR, and UKESM1-0-LL outperform the other two models with higher NSEs and better spatial correlation, especially in the water erosion regions. R-factor and 10-year storm EI estimated using MMEs (the arithmetic means of the aforementioned three models) for the historical period are generally underestimated, and the median biases are 0.80 and 0.66, respectively. Biases for each grid were determined as the bias-correction factors for future erosivity projection. Generally, most areas in eastern and central China are expected to experience larger rainfall erosivity. Under SSP1-RCP2.6 and SSP5-RCP8.5 scenarios, R-factor over mainland China is projected to increase by 18.9% and 19.8% for the near-term and 26.0% and 46.5% for the long-term, respectively; and 10-year storm EI is projected to increase by 14.2% and 17.4% for the near-term, and 14.9% and 45.0% for the long-term, respectively. The projected increases in rainfall erosivity are mainly due to the increasing probability of extreme precipitation. This implies that soil and water conservation measures in China need to be further strengthened to meet the challenges brought by the increasing number and magnitude of extreme events in the context of global warming.

Tillage is an important management practice that can be necessary to loosen the soil and allow for seeding and aims at enhancing productivity. However, the long-term effects of a particular tillage action on soil health depend on the local soil characteristics and differ amongst soils. The main aim of our study was to evaluate the possible effects of various physical, chemical, and biological soil quality indicators in dependence of three different tillage practices: Conventional Tillage (CT), Mulch Tillage (MT), and No-Till (NT). A long-term tillage experiment that started in 1994 in Mistelbach, Lower Austria, was comprehensively sampled in 2002 and 2021. The research attempts to fill the knowledge gap in the long-term soil health changes due to shifting conventional tillage. To evaluate the soil health changes over time, we assessed the impact of the three tillage practices on selected soil quality indicators in the 0-20 cm layer and below 20 cm, which we determined as being below the plowing depth. The "Soil Management Assessment Framework" (SMAF) procedure was applied to assess and compare the overall soil quality. Twenty-one indicators were selected to compare and evaluate the long-term effects of the three tillage systems (a.); fifteen indicators were used to investigate the temporal changes since the last monitoring (b.); thirteen indicators were selected to assess overall soil quality (c.). The study shows that the tillage practices and temporal conditions significantly affected soil organic carbon (SOC) content. The SOC amount in the 0-20 cm layer was twice as high under no-till (31.2 t/ha) compared to conventional tillage (15.3 t/ha). The SMAF reveals that NT increased SOC content and enhanced soil's physical indicators, such as available soil water, porosity, and coarse pores in the 0-20 cm layer. We found soil quality improvements with MT and NT in the 0-20 cm layer; however, the SMAF also indicates that the soil quality was better below 20 cm in 2021 compared to 2002, independent of the tillage practice. According to our results, conservation tillage practices (such as MT and NT) enhanced overall soil quality, particularly the physical (available soil water, coarse pores) and soil biological indicators, mainly SOC.

Every application of soil erosion models brings the need of proper parametrization, i.e., finding physically or conceptually plausible parameter values that allow a model to reproduce measured values. No universal approach for model parametrization, calibration and validation exists, as it depends on the model, spatial and temporal resolution and the nature of the datasets used. We explored some existing options for parametrization, calibration and validation for erosion modelling exemplary with a specific dataset and modelling approach. A modified version of the Morgan-Morgan-Finney (MMF) model was selected, representing a balanced position between physically-based and empirical modelling approaches. The resulting calculator for soil erosion (CASE) model works in a spatially distributed way on the timescale of individual rainfall events. A dataset of 142 high-intensity rainfall experiments in Central Europe (AT, HU, IT, CZ), covering various slopes, soil types and experimental designs was used for calibration and validation with a modified Monte-Carlo approach. Subsequently, model parameter values were compared to parameter values obtained by alternative methods (measurements, pedotransfer functions, literature data). The model reproduced runoff and soil loss of the dataset in the validation setting with R of 0.89 and 0.76, respectively. Satisfactory agreement for the water phase was found, with calibrated saturated hydraulic conductivity (k ) values falling within the interquartile range of k predicted with 14 different PTFs, or being within one order of magnitude. The chosen approach also well reflected specific experimental setups contained in the dataset dealing with the effects of consecutive rainfall and different soil water conditions. For the sediment phase of the tested model agreement between calibrated cohesion, literature values and field measurements were only partially in line. For future applications of similar model applications or datasets, the obtained parameter combinations as well as the explored methods for deriving them may provide guidance.

Project Co-ordinators: Dr. Jose Alfonso Gómez Calero (Instituto de Agricultura Sostenible (IAS-CISC), Dr. Weifeng Xu (Fujian Agriculture and Forest University, FAFU). -- Trabajo desarrollado bajo la financiación del proyecto “Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping Systems” (773903), coordinado por José Alfonso Gómez Calero, investigador del Instituto de Agricultura Sostenible (IAS)., Assessing regional sediment yield variation and their responses to the potential controlling factors are critical to develop specific strategies of soil conservation measures to adapt to future climate change. This study attempted to investigate the spatial–temporal variation of sediment load in the Wei River basin in the midstream of the Yellow River during 1961–2015 at 15 hydrological stations. The results indicated that annual sediment load in the past six decades decreased significantly (P < 0.01) with the changing trends of −6.43 × 104, −3.86 × 104, −4.6 × 104 t/a at Xianyang, Zhangjiashan, and Zhuangtou stations, respectively. Annual sediment load exhibited abrupt changes in the mid-1990s, which were largely attributed to the strong effects of soil conservation measures in the study area. The spatial pattern of soil erosion were characterized by high sediment yield in the north with sparse vegetation cover and well-developed gullies, and low sediment yield in the south with flat plain and good vegetation cover in the Wei River basin. The results of the partial least squares-structural equation model (PLS-SEM) showed that vegetation changes and rainfall variability explained 62.3%, 47.3%, and 40.1% of the variation in runoff at Xianyang, Zhuangtou, and Zhangjiashan stations, respectively, whereas 59.4%, 17.6% and 48% of the variation in sediment load were explained by the combining effects of rainfall variability, changes of vegetation and runoff. This study provides a deep insight for understanding the effects of driving forces on sediment yield changes, and can be useful to regional soil conservation planning in the region., The study was funded by the National Science and Technology Basic Resource Investigation Program (2017FY100904), the Chinese National Natural Sciences Foundation (42177323; 42077076), the Horizon 2020 Project Shui which is co-funded by the Chinese MOST (2017YFE0118100) and the European Union Project (773903).

Tillage practices are known to affect soil water retention, plant available water and, consequently, crop production. Therefore, adjusted and sustainable tillage practices may contribute to an efficient use of limited available water resources. Impacts of tillage can be determined by assessing soil hydraulic properties and crop characteristics. In this study, three tillage practices were investigated with respect to soil water distribution and crop development, with a specific focus on determining actual evapotranspiration (ET) and crop transpiration (T). T/ET ratios should give additional information on soil water availability and crop water use. The practices included conventional tillage, reduced tillage (no plow), and no-tillage and were investigated on a long-term rainfed field experiment with soybean (glycine max l. merr) planting. The long-term experimental field is located in Raasdorf in the agricultural region Marchfeld east of Vienna, Austria (48°14’ N, 16°35’ E; 156 m elevation a.s.l., average annual precipitation of approx. 497 mm). The field is separated in experimental plots of 960 or 1,440 m2. The measurements comprised automated monitoring of weather and soil water by means of a telemetric sensor network as well as manual monitoring of crop development. ET and its components were determined using an isotope-based water balance technique. ET rates were determined at the conventional experimental plot based on a water balance and verified with scintillometer measurements on a nearby field of 11.5 ha. In the researched vegetation period with limited water availability, the conservative tillage practices showed better water storage, water use, and crop yields compared to the conventional practice. The weekly T/ET ratios progressed according to the canopy development, which was affected by the tillage-induced soil conditions. In this context, delayed plant development – specifically at the no-till plots – led to extended green cover and productive water use during the late season, where a large part of the precipitation has fallen. The tillage-induced difference of wetness at soil surface, however, did not have a substantial effect on T/ET; even soil evaporation was similar at all plots. Furthermore, the ratios showed the beneficial effect of mulch protection regarding unproductive losses by evaporation, in particular during the initial periods of crop emergence and development. Thus, the assessment of T/ET ratios improved the insights in impacts of management practices and showed potential to promote the efficient use of the available water resources.

Zusammenfassung Die Wirkung unterschiedlich intensiver Regenereignisse auf Splash-Erosion ist noch nicht genau bekannt. Um diese zu untersuchen, wurde sandiger Lehm in einem Laborversuch durch einen Starkregensimulator mit zunehmender, abnehmender oder konstanter Regenintensität beregnet. Alle Intensitätsabfolgen wiesen im Mittel eine Regenintensität von 24,7 mm h−1 auf und bestanden aus drei Intensitätsstufen mit einer Beregnungsdauer von je 20 min. Der ausschließlich durch Splash-Erosion abgetragene Boden wurde nach jeder Beregnungsphase gesammelt. Die Ergebnisse zeigen, dass Regenereignisse mit hoher Intensität am Anfang zu 32 % mehr Splash-Erosion führen als jene mit maximaler Intensität am Ende. Die kumulativ wirkende kinetische Energie der Regentropfen, verstärkt durch einen dünnen Wasserfilm auf den Proben, führt dazu, dass die Splash-Erosion am Ende einer Simulation stärker wirkt als zu Beginn. Aus den Untersuchungsergebnissen kann zudem durch Extrapolation der Regressionsgeraden eine minimale Regenintensität zwischen 10 mm h−1 und 15 mm h−1 zur Erzeugung von Splash-Erosion angenommen werden.

The effect of long-term (about 25 years) use of different farming practices on a set of soil properties and development of erosion in Lower Austria has been studied. Three tillage systems—zero, or no-till (NT); minimum, or conservation (CS); and conventional (CV)—are compared. The comparison demonstrates that the properties of Typic Argiudols (Luvic Phaeozems), formed on steep (13.2%) slopes, change depending on both the tillage type and the position on the slope. Unlike the CV tillage, the soil-saving technologies provide higher contents of nutrients, silt, and clay, as well as better water permeability and water stability of soil aggregates. Despite an almost doubled amount of lumpy fractions (>10 mm), the soil aggregate states after NT and CS tillage are estimated as “excellent”. Independently of the tillage system, all agrochemical, electrophysical, and hydrophysical parameters (except for pH and bulk density) increase downward the slope, which is associated with erosion, namely, the washout of suspended sediments by water flows. The Corg content in the soil tightly correlates with the water stability of soil aggregates (r = 0.91), the concentration of soluble humic substances and fine solids (SAK; r = 0.76), and electroconductivity (r = 0.75). An anti-erosion efficiency of tillage practice increases in the series CV–CS–NT. The NT or CS systems are recommended for the erosion-prone slopes of Alpine foothills.

The Lake Basaka catchment (Ethiopia) has undergone a significant land use–land cover (LULC) change and lake level rise over the past five decades. Significant quantities of water and sediment flow annually into the lake through erosion processes. An appropriate method of estimating the surface run‐off from such ungauged and dynamic catchment is extremely important for delineating sensitive areas (based on run‐off responses) to be protected and for development of suitable measures to reduce run‐off and associated soil loss. Reliable prediction of run‐off, however, is very difficult and time‐consuming for catchments such as that of Lake Basaka. The present study estimated the dynamics of surface (direct) run‐off using the NRCS‐CN model in ArcGIS, assisted by remote sensing and ancillary data. The results indicated the Lake Basaka catchment experienced significant temporal and spatial variability in its run‐off responses, depending on the rainfall (amount and distribution) pattern and LULC changes. A significant run‐off increase occurred after 1973, consistent with significant LULC changes and lake level increments occurring after that period. A reduced vegetation cover also resulted in increased run‐off coefficient of the lake catchment from 0.11 in the 1970s to 0.23 in the 2000s, indicating the important need to consider possible future LULC evolution when forecasting the lake catchment run‐off behaviour.

Project Co-ordinators: Dr. Jose Alfonso Gómez Calero (Instituto de Agricultura Sostenible (IAS-CISC), Dr. Weifeng Xu (Fujian Agriculture and Forest University, FAFU)., Stable isotope techniques can be used to investigate evapotranspiration and its partitioning into evaporation and transpiration. However, verification is often difficult due to missing information about actual evapotranspiration. Therefore, in this study a methodology tested for laboratory conditions was modified for field applications. Evapotranspiration, which was determined by weighing lysimeters, and isotope techniques were combined with soil water and lysimeter measurements to calculate evaporation and transpiration rates of soybean under natural conditions. The case study was conducted in 2019 in Groß-Enzersdorf, Austria. The results show that the methodology was suited to measure actual variations of evaporation and transpiration ratios, even during dry periods. Weekly evaporation (0.5–2.2 mm d−1) and transpiration (1.3–4.3 mm d−1) rates as well as the respective ratios (transpiration 43–85%) agreed with the results of numerical modelling and values from the literature, confirming the applicability of the modified methodology for portioning evapotranspiration in the field., This work was supported by the European Union’s Horizon 2020 Framework Programme [773903].

Freshwater is a scarce resource facing a growing demand. One aspect of this growing demand arises from the expansion and intensification of crop production on irrigated land. To preserve valuable water resources, agricultural water management must aim at an efficient use of water. This can be approached by facilitating sufficient water supply for optimal crop transpiration (T) and thus crop production, and at the same time reduce unproductive water losses due to soil evaporation (E). In this regard, knowing the ratios of E and T and how they are affected by environmental and management conditions is required to develop, adapt, and evaluate agricultural practices with respect to efficient water use.The study aimed at applying a modified E-T-partitioning method to evaluate irrigation and how varying water availability affected E and T ratios. Field experiments were conducted 2019 in Groß-Enzersdorf in the agricultural region Marchfeld east of Vienna, Austria (48°12’ N, 16°34’ E; 157 m elevation a.s.l., average annual precipitation of approx. 540 mm). A conventionally managed field was planted with soybean (glycine max l. merr) and irrigated twice with a hose reel irrigation machine. Partitioning of evapotranspiration (ET) was analyzed using an adapted water balance and stable isotope mass balance method. Monitoring throughout the soybean vegetation period comprised weekly analyses of the isotopic composition of soil samples, the profile water content in 10 cm steps down to 80 cm, weather data, the isotopic signatures of precipitation and irrigation water, ET, and crop growing stages. ET was measured with eddy covariance technique, and isotopic fractionation for determining E and T ratios was calculated from measured boundary conditions.Weekly T ratios from blossom to beginning of maturation of soybean ranged from 56 to 84 %, which is in agreement with studies based on comparable partitioning methods. The relation between E and T did not only progress according to the canopy development but also responded to water availability in the rooting zone. During the vegetative growth stage, for example, the proportion of T was larger at partial canopy cover and sufficient water availability (from spring precipitation) compared to full canopy cover and when facing soil water stress. When soil surface was dry, E dropped to almost zero. On the other hand, a wetted surface substantially raised the E, even under closed canopy. Multiple small rain events during full canopy cover mainly contributed to E. As the analyses sufficiently revealed the relations of E and T ratios to changing boundary conditions, the method proved useful to evaluate irrigation events and strategies and deduce further improvements. In case of using a hose reel irrigation machine, the results suggest an intensification of the individual watering. However, a quantitative relationship between irrigation and the amount of water used for T would require shorter evaluation intervals of 2-3 days.

Trabajo desarrollado bajo la financiación del proyecto “Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping Systems” (773903), coordinado por José Alfonso Gómez Calero, investigador del Instituto de Agricultura Sostenible (IAS)., The quantitative prediction of hydrological components through hydrological models could serve as a basis for developing better land and water management policies. This study provides a comprehensive step by step modelling approach for a small agricultural watershed using the SWAT model. The watershed is situated in Petzenkirchen in the western part of Lower Austria and has total area of 66 hectares. At present, 87% of the catchment area is arable land, 5% is used as pasture, 6% is forested and 2% is paved. The calibration approach involves a sequential calibration of the model starting from surface runoff, and groundwater flow, followed by crop yields and then soil moisture, and finally total streamflow and sediment yields. Calibration and validation are carried out using the r-package SWATplusR. The impact of each calibration step on sediment yields and total streamflow is evaluated. The results of this approach are compared with those of the conventional model calibration approach, where all the parameters governing various hydrological processes are calibrated simultaneously. Results showed that the model was capable of successfully predicting surface runoff, groundwater flow, soil profile water content, total streamflow and sediment yields with Nash-Sutcliffe efficiency (NSE) of greater than 0.75. Crop yields were also well simulated with a percent bias (PBIAS) ranging from −17% to 14%. Surface runoff calibration had the highest impact on streamflow output, improving NSE from 0.39 to 0.77. The step-wise calibration approach performed better for streamflow prediction than the simultaneous calibration approach. The results of this study show that the step-wise calibration approach is more accurate, and provides a better representation of different hydrological components and processes than the simultaneous calibration approach., This research was performed within the project “Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping systems (SHui)”. Financial support was provided by the European Union, Grant Nr. 773903 and the Chinese Ministry of Science and Technology under CFM (China-EU Co-Funding Mechanism).

Besides the importance of dissolved organic matter (DOM) in soil biogeochemical processes, there is still a debate on how agricultural intensification affects the leaching of terrestrial DOM into adjacent aquatic ecosystems. In order to close this linkage, we conducted a short-term (45 day) lysimeter experiment with silt loam and sandy loam undisturbed/intact soil cores. Mineral (calcium ammonium nitrate) or organic (pig slurry) fertilizer was applied on the soil surface with a concentration equivalent to 130 kg N ha&minus, 1. On average, amounts of leached DOC over 45 days ranged between 20.4 mg (silt loam, mineral fertilizer) and 34.4 mg (sandy loam, organic fertilizer). Both, mineral and organic fertilization of a silt loam reduced concentration of dissolved organic carbon (DOC) in the leachate and shifted its composition towards a microbial-like signature (BIX) with a higher aromaticity (Fi) and a lower molecular size (E2:E3). However, in sandy loam only mineral fertilization affected organic matter leaching. There, lowered DOC concentrations with a smaller molecular size (E2:E3) could be detected. The overall effect of fertilization on DOC leaching and DOM composition was interrelated with soil texture and limited to first 12 days. Our results highlight the need for management measures, which prevent or reduce fast flow paths leading soil water directly into aquatic systems, such as surface flow, fast subsurface flow, or drainage water.

Soil erosion through various water processes is a worldwide problem. This research is focused on raindrops’ impact on soil surfaces, which is generally considered the initial stage of the erosion process. Splash erosion monitoring was conducted across three experimental sites: Petzenkirchen, Mistelbach (Austria) and Prague (Czech Republic). At each site, the rainfall characteristics (intensity and kinetic energy) were measured by rain gauges and disdrometers, and the impacts on soils (soil loss, soil surface consolidation, changes in soil surface roughness) were evaluated. Several disturbed soil samples with an area of 78.5 cm2 were placed into splash cups prior to each event. The splash cup collects the soil particles that are splashed out of the sample area when a raindrop hits the soil surface. The collected sediment suspension is processed in the laboratory after each event to determine the lost soil mass. Ground photogrammetry was utilized to determine the surface consolidation of a sample caused by a given rainfall event. Results for more than 500 soil samples were included in this study. Relationships between kinetic energy, rainfall intensity and soil loss and consolidation were evaluated.

Soil erosion and runoff data are collected at three sites in eastern Austria using field erosion plots. Observed treatments include 1) conventional tillage with plough (CT), 2) mulch tillage with winter cover crop (MT), and 3) no-till with winter cover crop (NT). Data cover a time span from 1994 to 2018. They include data about surface runoff, soil loss, nitrogen, phosphorus and soil organic carbon losses as well as cop yields associated with the erosion processes. Interpretation of the data will be found in “Long-term experience with conservation tillage practices in Austria: impacts on soil erosion processes” [1].

Rainfall kinetic energy (KE) is an important indicator for the potential soil loss due to rainfall in erosion risk assessment. Kinetic energy-intensity (I) relationships have been developed as a means to calculate the KE of rainfall, when only the rainfall intensity is known. The direct measurement of KE has been enabled due to the use of disdrometers, which measure the size and velocity of raindrops. Previous measurements have shown that rainfall measurements for the same site differed among disdrometer types. Therefore, the best fitting KE-I relationship is likely dependent on the type of disdrometer. In this study, the influence of the disdrometer-specific drop size and velocity measurements on the formulation of new KE-I relationships as well as the fit of existing equations from literature was investigated. Disdrometer rainfall data was collected in 1-minute intervals from six laser-based disdrometers. Two disdrometers of each of the following three types were compared: the PWS100 Present Weather Sensor from Campbell Scientific, the Laser Precipitation Monitor from Thies Clima and the first generation Parsivel from OTT Hydromet. The disdrometers were set up individually at sites in Austria, Czech Republic and New Zealand. Rainfall was measured between 2014 and 2019 with varying amounts of collected data for each site. The results revealed the inherent differences in drop size and velocity distribution estimation between different types of devices. The same pattern of rainfall drop size and velocity distribution could be seen for disdrometers of the same type despite spatial separation. This indicates that actual spatial differences in rainfall characteristics may be difficult to discern when comparing data from different types of disdrometers. New exponential KE-I relationships based on disdrometer data were formulated for each site and device. To confirm the use of the new KE-I equations, one of the equations was validated using rain gauge data from the same site. The best fit of literature KE-I equation varied among sites and devices. The relationship employed in the Revised Universal Soil Loss Equation (RUSLE) always underestimated KE with a percent bias ranging from -2 to -30 %. This study highlights the differences in disdrometer rainfall kinetic energy measurements and how these influence the formulation and evaluation of KE-I relationships, which are important in rainfall erosivity studies.

Hydrological models enable comprehensive examination, understanding and quantification of hydrological processes in catchments under the influence of different characteristics. The Soil and Water Assessment Tool (SWAT) has the ability to predict the impact of land management practices on water, sediment and agricultural chemical yield in such catchments.The objective of this study is to apply the SWAT model on a small agricultural watershed, calibrate and validate it with measured flow, sediment and crop yield data. The model is set up for the HOAL catchment in Petzenkirchen, Lower Austria. The catchment has an area of 66 hectares. The climate is humid with mean annual temperatures of around 10°C, and annual precipitation of around 800 mm. Soils include Cambisols and Planosols with medium to poor infiltration capacities. Gleysols occur close to the stream. At present, 87% of the catchment area is arable land, 5% is used as pasture, 6% is forested and 2% is paved. The agricultural activities mainly involve wheat based crop rotation including winter wheat, winter barley, sweet and silage corn and canola. The catchment is divided into 37 fields and for each field exact information about tillage date and type of implement used, date of planting and harvest, date and amount of fertilization and plant protection are available. This information is incorporated in the model during set up. The procedures of model set up, sensitivity analysis, calibration and validation are outlined. A Sequential Uncertainty Fitting (SUFI-2) procedure within SWAT-CUP is used to auto-calibrate and validate the model. The model calibration (2012-2014) and validation (2015-2017) is based on the observed daily discharge and daily sediment concentration at the watershed outlet. Event based observations of runoff and sediment yield from two sub-watersheds are available as well as measured soil water contents at 30 points and crop yield data from different fields. Stream flow and sediment calibration are performed at the watershed outlet as well as at sub watershed level. Results of the SWAT model capability to predict flow, sediment and crop yield as well as soil water contents in the small watersheds will be presented.

Knowledge and quantification of water fluxes within the soil-vegetation-atmosphere continuum is fundamental to understand ecohydrological systems. It is also essential to further develop water management practices and irrigation systems in times of increasing needs for water and rising water scarcity. A major component in this regard is evapotranspiration (ET) as it links the energy balance and the water balance. Evapotranspiration can be fractionated into productive water fluxes through plants’ stomata (transpiration) and non-productive water loss from soil surface (evaporation). Determination and understanding of factors influencing this ratio are assumed to help improving water use efficiency through best management practices in agriculture, especially in water limited environments. Aim of this study was to adapt a stable isotope mass balance method for determining evapotranspiration and its components transpiration and evaporation for soybeans under natural conditions.The study site was in Groß-Enzersdorf, east of Vienna, Austria (48°12’ N, 16°34’ E; 157 m elevation a.s.l.). The study period covered the vegetation period of soybeans in 2019. Crop evapotranspiration was determined using a weighing lysimeter with 1.8 m diameter. For the fractionation, a stable isotope mass balance method from literature was adapted and further developed for soybeans under natural (stressed) climatic conditions. The underlying principle of isotope fractionation is that different physical properties of naturally occurring stable isotopes in water cause shifts in the isotopic composition due to evaporation. Therefore, evaporation causes enrichment of heavier stable isotopes in the near surface soil water, whereas water uptake by plant roots does not cause considerable partitioning in soil water. This allows determination of both fractions, assuming all other water balance components are known. Soil samples for the stable isotope mass balance were taken near a weighing lysimeter (1.8 m diameter). Evapotranspiration determined by the lysimeter provided the basis for the mass balance fractionation calculations. Monitoring throughout the soybeans vegetation period included weekly analyses of isotopic composition of soil samples, measurements of water content over the soil profile in 10 cm steps down to 80 cm, weather data, and crop growing stages.Results reveal a plausible course of soybean evapotranspiration and its components. The preliminary designed method of soil water sampling could be adequately adapted to determine representative isotopic soil profiles for water balance determination under the given conditions. Water extraction from the soil samples worked well under moist as well as very dry soil conditions. Further data analysis was done to assess applicability of the modified method to determine fractionation ratios for different plant development stages. The available results encourage further experiments to test and investigate the versatility of this method with respect to different soil cultivation methods for a water use efficiency review.

On agricultural fields, management (especially tillage) operations with a distinct orientation often lead to a corresponding preferred orientation of surface runoff and associated sediment transport. When deriving surface properties like flow directions and slope for runoff modelling from digital elevation model (DEM) data with grid sizes larger than 1m, these features of the surface will usually remain undetected and by default predict runoff and sediment transport patterns based on the topographic slope and flow directions alone.A methodology proposed by (Takken et al., 2001) involves calculating 1) topographic slope and flow directions and 2) slope and flow directions assuming that surface runoff takes place exclusively along the tillage orientation. A decision algorithm then decides for each grid cell, whether 1) or 2) is to be used, based on cell slope, oriented roughness and the angle between topographic and tillage-controlled flow directions. An exception is made for distinct thalweg situations, where 1) is always used.For larger areas, where the manual assignment of the management direction of individual fields (e.g. based on orthophotos) is not feasible, automatic estimation of a field’s tillage orientation is done using field geometry parameters and assuming tillage taking place in the direction of the longest field extent.The output of the methodology is to be used subsequently in grid-based soil erosion modelling and is expected to provide more realistic results of surface runoff and soil loss patterns. Initial tests using the output flow directions and slope of the method as input for an MMF (Morgan-Morgan-Finney) based soil erosion model in a small experimental catchment (0.7 km²) show surface runoff and soil loss concentrating on the field borders (headlands) for some fields, potentially leading to a shift of priority for protection of either whole individual fields or particularly affected portions of fields.The improved modelling results can in some situations be significant for decisions on the placement of best management practices (BMP) that intend to limit either soil loss from the field or sediment input into adjacent surface water bodies (e.g. vegetated filter strips, grassed waterways or the feasibility of contouring), since these measures might be rendered useless, when their placement is based on topographic flow directions alone, as is the default practice.

Soil erosion by water is globally the main soil degradation process which leaves serious consequences on agricultural land and water aquifers. Splash erosion is the initial stage of soil erosion by water, resulting from the destructive force of rain drops acting on soil surface aggregates. Splash erosion studies conducted in laboratories use rainfall simulators. They produce artificial rainfall which can vary according to type of the rainfall simulator. In this study the aim was to quantify the differences in splash erosion rates affected by rainfall produced by two different rainfall simulators on two silt loam and one loamy sand soil. Splash erosion was measured using modified Morgan splash cups and the rainfall simulators were equipped with four VeeJet or one FullJet nozzle. The soil samples placed under simulated rainfall were exposed to intensity range from 28 to 54 mm h-1 and from 35 to 81 mm h-1, depending on the rainfall simulator. Rainfall characteristics such as drop size and velocity distribution were measured with an optical laser disdrometer Weather Sensor OTT Parsivel Version 1 (Parsivel) by OTT Messtechnik. Rainfall simulator with VeeJet nozzles produced smaller drops but higher drop velocity which resulted in higher kinetic energy per mm of rainfall compared to rainfall simulator with FullJet nozzles. For the same intensity rate measured kinetic energy under the rainfall simulator with VeeJet nozzles was 45% higher than rainfall kinetic energy from rainfall simulator with FullJet nozzles. Accordingly, the average splash erosion rate was 45 and 59% higher under the rainfall simulator with VeeJet nozzles for one silt loam and loamy sand soil, respectively. Splash erosion was found to be a linear or power function of the rainfall kinetic energy, depending on rainfall simulator. The obtained results highlight the sensitivity of the splash erosion process to rainfall characteristics produced by different rainfall simulators. The heterogeneity of rainfall characteristics between different types of rainfall simulators makes a direct comparison of results obtained from similar erosion studies difficult. Further experiments including comparison between more rainfall simulators could define influencing rainfall parameters on splash erosion under controlled laboratory conditions.

Besides the importance of dissolved organic matter (DOM) in soil biogeochemical processes, there is still a debate on how agricultural intensification affects the composition and concentration of dissolved organic matter leached from soils into adjacent aquatic ecosystems. In order to investigate the immediate response of DOM leaching to fertilization, we conducted a short-term (45 day) lysimeter experiment with undisturbed silt loam and loamy sand soil cores. Mineral (calcium ammonium nitrate) or organic (pig slurry) fertilizer was applied on the soil surface with a concentration equivalent to 130 kg N ha−1. After fertilization, soil leachate was collected in 6-days intervals. Dissolved organic carbon concentrations (DOC) were measured with gas chromatography, while shifts in DOM composition were analysed using absorbance and excitation- emission fluorescence indices from peak-picking as well as from PARAFAC analysis. During the first 12 days, fertilization of a silt loam reduced DOC concentrations in the leachate and shifted its composition towards more microbial- like compounds. Additionally, the discrepancy in DOM composition between fertilizer and control treatments of a silt loam increased with time. However, in loamy sand only mineral fertilization affected organic matter leaching and decreased DOC concentrations in the leachate during the first 12 days. Furthermore, mineral fertilization of the loamy sand led to DOM compounds with low molecular size in the first 12 days. Our results show that fertilization tends to increase microbial transformed DOM, while it reduces leached DOC concentrations. Furthermore, the magnitude of fertilization on DOC concentrations and DOM composition was highly depending on the soil texture they originate from. However, in our set-up, the experimental soil units were restricted to a soil depth of 16 cm (Ap horizon). At ecosystem level, a sufficiently long soil passage might mitigate the impact of fertilization on soil DOM.

This article outlines the major scientific objectives of the SHui project that seeks to optimize soil and water use in agricultural systems in the EU and China, by considering major current scientific challenges in this area. SHui (for Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping systems) is large cooperative project that aims to provide significant advances through transdisciplinary research at multiple scales (plot, field, catchment and region). This paper explains our research platform of long-term experiments established at plot scale, approaches taken to integrate crop and hydrological models at field scale; coupled crop models and satellite-based observations at regional scales; decision support systems for specific farming situations; and the integration of these technologies to provide policy recommendations through socio-economic analysis of the impact of soil and water saving technologies. It also outlines the training of stakeholders to develop a basic common curriculum despite the subject being distributed across different disciplines and professions. As such, this article provides a review of major challenges for improving soil and water use in EU and China as well as information about the potential to access information made available by SHui, and to allow others to engage with the project., This work has been supported by Project SHui which is co-funded by the European Union Project GA 773903 and the Chinese MOST. This work has been supported by P12-AGR-0931 (Andalusian Government), RTA2014-00063- C04-03 (Spanish government), SHui (European Commission Grant Agreement number: 773903) and EU‒FEDER funds

Developing countries with an increasing population like Ethiopia experience degradation of land and water resources. To tackle this problem soil and water conservation (SWC) has been practiced and recently promoted by the Ethiopian government. However, the effectiveness of SWC practices on runoff and soil erosion have not been studied in detail for their long- and short-term effects. An integrated measurement and modeling study was conducted from 2012 to 2014 in the Gumara-Maksegnit sub watershed to assess the impacts of SWC structures on runoff and sediment yield using the Geospatial Interface for the Water Erosion Prediction Project (GeoWEPP) model. The study was conducted in two adjacent, smaller watersheds where SWC structures were constructed in one of the watersheds (treated sub watershed), while the other one was a control watershed without SWC structures (untreated sub watershed). The treated sub watershed has an area of 27.1 ha and the untreated sub watershed has an area of 31.7 ha. Runoff and sediment yield were compared based on the observations and GeoWEPP model simulations. The GeoWEPP model simulation results predicted the daily runoff satisfactorily for both sub watersheds (R2 = 0.68 and NSE = 0.43 for untreated and R2 = 0.61 and NSE = 0.84 for treated sub watershed). Similarly, the model prediction showed satisfactory results in sediment yield (R2 = 0.61 and NSE = 0.59 for untreated and R2 = 0.57 and NSE = 0.81 for treated sub watershed). SWC structures reduced slope gradient and changed flow accumulation. The observation and simulation study concluded that the treated sub watershed surface runoff was reduced by about 19% as compared to the untreated sub watershed. Similarly, the model estimated that SWC structures constructed in the treated sub watershed reduced the total area that generates soil loss above the set target limit of 10 t ha−1 y−1 from 49% to 38% of the watershed area. SWC has led to a significant reduction in sediment yield by 28 to 38% in these highland watersheds of Ethiopia. The results confirmed that SWC structures have a significant impact to prevent land degradation in the Ethiopian highlands.

In recent years, Compound Specific Stable Isotope (CSSI) techniques have enabled promising new tracers to track land-use-specific sediment sources. However, empirical data exploring the technique, particularly under controlled conditions, is still scarce. Hence, the main goal of this study is to explore the suitability of CSSI to identify sediment sources under different land use in the small agricultural site of Mistelbach (8.7 ha) located in Austria. In a previous study, the authors quantified, with a 137 Cs-based reconnaissance approach, a sedimentation magnitude of 4 mm year − 1 in the deposition zone at the outlet of that study site. To obtain detailed information on the sediment provenance, CSSI techniques based on the measurement of δ 13 C signatures of natural fatty acids (FAs), were used. A cost effective sampling approach involving composite sampling, identified potential sediment source materials from the four main agricultural fields. Two long-chain FAs (i.e. C22:0 = behenic acid; C24:0 = lignoceric acid) as well as bulk δ 13 C allowed the best statistical discrimination for apportioning the origin of the sediments. Four mixing models (i.e. IsoSource, SIAR, MixSIAR and SIMMR) applied to the data generated similar results. IsoSource performed as well as the other Bayesian models tested. The main grazed waterway of the basin, identified as one of the four sources of the sediment, was evaluated to have contributed 55.1 ± 5% (IsoSource), 53.9 ± 2.7% (SIAR), 53.9 ± 2.7% (MixSIAR) and 54.0 ± 2.7% (SIMMR) to the sediment. The estimated contributions of the sources to the sediment are consistent with the land use information and the distance of the sources to the outlet. More than 80% of the sediment deposited at the basin exit originates from the two sources which had maize cultivation, one of the more erosive crops, in particular at the beginning of the growing season. This study emphasizes that CSSI and 137 Cs techniques are complementary for establishing land sediment redistribution. Their combined use could provide key decision support knowledge for optimised decision-making of land managers to ensure the sustainability of agro-ecosystem management.

Under conditions of climate change, the severity and probability of storm events and droughts are expected to increase, this may affect the partitioning into surface and subsurface runoff. However, there is still a debate on how such extreme weather conditions affect the leaching of soil organic carbon. The aim of this study was to ascertain the impact of rainfall intensity (63 vs 79 mm h−1) and antecedent soil moisture (Matric potential: −10 hPa vs −450 hPa) on flow partitioning in the transportation (fluxes and timing) of dissolved (DOC) and particulate organic carbon (POC). Rainfall simulation experiments using undisturbed soil monoliths (1 m × 0.5 m × 0.3 m) allowed to monitor the transport of water, sediments, DOC, and POC via surface and shallow subsurface runoff. In addition, the composition of the leached organic matter was analysed using photometric and fluorometric methods. Most of the organic carbon was transported as POC via surface runoff. In the surface runoff, the influence of antecedent soil moisture on POC loss was larger than rainfall intensity, while rainfall intensity had a greater influence on DOC losses. Under initially unsaturated conditions, surface sealing reduced the infiltration rate, thus fuelling the total surface runoff, which, in turn, enhanced the transported total sediment and POC load of the surface runoff. While POC dominated surface runoff, DOC played a crucial role in the subsurface runoff with higher DOC concentrations under unsaturated conditions. In contrast to other treatments, DOC exported from unsaturated soils rained with high intensity had a unique composition with the highest proportion of humic-like peaks (A, M, C), protein-like peaks (T) and components (C4), suggesting a concentrating effect on DOC at those soils. Altogether, this research acquires new insights into how flow partitioning under extreme weather conditions affects organic carbon losses and which transport mechanism might pose a risk for aquatic systems.

SummaryCover cropping is a key agro-environmental measure in Europe. Cover crops may reduce N2O emissions by reducing soil nitrate content, while easily decomposable residues can enhance greenhouse gas losses. In a field study, emissions from the cover cropped fields compared to the fallow at two climatically different sites (semi-arid vs. humid) in Austria were measured with closed chambers and different driving factors were studied. The height of post-cover crop emissions was compared to gaseous losses during the management operations in the subsequent main crop maize. N2O and CO2emissions following the cover crops were low even at high emission moments compared to the losses induced by the main crop management operations. Highest risk of N2O losses was from mustards due to low C/N ratio and possibly as a consequence of glucosinolate decomposition. CO2emissions in the cover cropped plots were generally higher compared to the fallow, indicating an enhanced soil microbiological activity. Dissolved organic carbon was found as a sensitive indicator related to the greenhouse gas emissions. We concluded that the environmental benefits from cover cropping are not achieved at the cost of an enhanced greenhouse gas emission and that pure stands of late sown brassica cover crops should be avoided to prevent any risk of increased N2O losses.

Optical disdrometers can be used to estimate rainfall erosivity; however, the relative accuracy of different disdrometers is unclear. This study compared three types of optical laser-based disdrometers to quantify differences in measured rainfall characteristics and to develop correction factors for kinetic energy (KE). Two identical PWS100 (Campbell Scientific), one Laser Precipitation Monitor (Thies Clima) and a first-generation Parsivel (OTT) were collocated with a weighing rain gauge (OTT Pluvio2) at a site in Austria. All disdrometers underestimated total rainfall compared to the rain gauge with relative biases from 2% to 29%. Differences in drop size distribution and velocity resulted in different KE estimates. By applying a linear regression to the KE–intensity relationship of each disdrometer, a correction factor for KE between the disdrometers was developed. This factor ranged from 1.15 to 1.36 and allowed comparison of KE between different disdrometer types despite differences in measured drop size and velocity.

In this study, the effect of land use–land cover change (LULCC) on surface (direct) runoff was estimated for Lake Basaka catchment using the soil conservation services—curve number model in the geospatial information system (ArcInfo), assisted by remote sensing. The result indicated that Lake Basaka catchment experienced a significant LULCC. About 86% of forest coverage and 46% of grasslands were lost over the study period (1973–2015), which were shifted to open bushy woodlands, farms, lake water and wetlands. The runoff responses were observed to be increasing since 1970s, especially after the inception of large-scale irrigation schemes to the region. The highest increase of surface runoff was observed to occur after mid-1980s, which is in line with the significant LULCC and the corresponding increment of lake level in that period. The reduction in vegetation cover has resulted in an increase of runoff coefficient (rc) from 0.07 in the 1960s to about 0.23 in 2000s. The sensitivity analysis result indicated that about 70% of the increase runoff rate in the lake catchment is attributed to LULCC, and the remaining proportion is due to rainfall. However, the effect of extreme rainfall on runoff process could not be underemphasized since it has significant impact especially during extreme events (observed rc of 0.33 in 2008). Overall, when predicting the runoff response of the lake catchment, it is importance to take into account possible future LULCC and evolution.

Soil erosion by water is one of the most severe soil degradation processes. Splash erosion is the initial stage of soil erosion by water, resulting from the destructive force of rain drops acting on soil surface aggregates. Apart from rainfall properties, constant soil physical properties (texture and soil organic matter) are crucial in understanding the splash erosion. However, there is lack of information about the effect of variable soil properties such as soil initial water content and surface condition (seal formation) on splash erosion. The objective of the present study was to determine how initial water content and surface condition affected soil splash erosion under simulated rainfall. The changes in soil surface condition were characterized by hydraulic variability (saturated hydraulic conductivity) due to surface seal formation. Slit loam and loamy sand soil textures were used in the experiment. The soil samples were collected from the top layer; air dried, and filled into modified Morgan splash cups for splash erosion measurements. Rainfall was created in the laboratory using two types of rainfall simulators covering intensity range from 28 to 54 mm h−1 and from 35 to 81 mm h−1. The soil samples were exposed to three consecutive rainfall simulations with different time intervals between simulations and different initial water content and surface conditions (air-dried, wet-sealed, and dry-crusted). Wet-sealed soil samples had up to 70% lower splash erosion rate compared to air-dried samples, due to surface ponding followed by seal formation. A significant decrease in soil saturated hydraulic conductivity indicated the formation of surface seal for silt loam soils. A non-significant decrease in saturated hydraulic conductivity for loamy sand soil was attributed to earlier formation of stable seals. Two different rainfall simulators produced different amount of splash erosion rates; however, the splash erosion development for increasing rainfall intensity was almost equal considering same initial surface condition. These results provide insight into dynamic changes of individual soil parameters affected by rainfall, and could find wider application for more complex soil erosion prediction models.

A soil map of a watershed provides a wealth of knowledge and can be vital for implementing site-specific soil managements. Hence, watershed-based soil assessment was conducted to select an optimum spatial interpolation method, while aiming for sustainable soil managements. Intensive soil sampling was undertaken to investigate the performance of ordinary kriging (OK), inverse distance weighting (IDW), and radial basis functions (RBF) for predicting the spatial distribution of soil texture, pH, soil organic carbon (SOC), and available phosphorus (AP). The 72 ha study area was divided into a 100 x 100 m grid and approximately at the center of each grid, topsoil samples (roughly from 10-25cm depth) were collected from over 75 locations across the entire watershed. The exponential and Gaussian models were best fitted in the semivariogram of measured soil. The performance of each interpolation method was assessed quantitatively in terms of Nash-Sutcliffe efficiency (E), coefficient of determination (R2), and index of agreement (d). The interpolated maps generated based on the highest value of E displayed OK was best performed for SOC and sand. RBF was most suitable for mapping of AP and clay, while IDW gave better results when applied to pH. The highest value of R2, E, and d (0.51, 0.51, and 0.83, respectively) resulted from the spatial interpolation of AP. Overall, the cross-validation statistics for each interpolation method showed there was no single method that significantly outperformed the others. Therefore, one of the interpolation methods could be applied for surface map generation in future studies of similar regions.