Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2019
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Nitrogen (N) losses from agricultural areas, especially into drinking water and marine environments, attract substantial attention from governments and scientists. This study analysed nitrogen loss from runoff water using long-term monitoring data (1994–2016) from the Skuterud catchment in southeastern Norway and the Naurstad catchment in northern Norway. Precipitation and runoff were lower in the Skuterud catchment than in the Naurstad catchment. However, in the Skuterud catchment, the annual total N (TN) losses ranged from 27 to 68 kg hm−2. High precipitation (1247 mm) in the Naurstad catchment resulted in substantial runoff water (1108 mm) but relatively low total TN losses ranged from 17 to 35 kg hm−2. The proportion of nitrate losses to TN loss was 51–86% and 28–50% in the Skuterud and Naurstad catchments, respectively. Furthermore, the monthly average TN concentrations and nitrate losses had two peaks, in April–May and October, in the Skuterud catchment; however, no significant fluctuations were found in the Naurstad catchment. The contributions of N and runoff water to TN and nitrate losses were calculated using multiple linear regression, and runoff water was the major contributor to TN loss in both catchments. Runoff water was the main factor in the Skuterud catchment, and the nitrate-N concentration was the main factor in the Naurstad catchment.
Authors
Hermine Mitter Anja-K. Techen Franz Sinabell Katharina Helming Kasper Kok Jörg A. Priess Erwin Schmid Benjamin L. Bodirsky Ian Holman Heikki Lehtonen Adrian Leip Chantal Le Mouel Erik Mathijs Bano Mehdi Melania Michetti Klaus Mittenzwei Olivier Mora Lillian Øygarden Pytrik Reidsma Rudiger Schaldach Martin SchönhartAbstract
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Knowledge of soil microtopography and its changes in space and over time is important to the understanding of how tillage influences infiltration, runoff generation and erosion. In this study, the use of a terrestrial laser scanner (TLS) is assessed for its ability to quantify small changes in the soil surface at high spatial resolutions for a relatively large surface area (100 m2). Changes in soil surface morphology during snow cover and melt are driven by frost heave, slaking, pressure exertion by the snowpack and overland flow (erosion and deposition). An attempt is undertaken to link these processes to observed changes at the soil surface. A new algorithm for soil surface roughness is introduced to make optimal use of the raw point cloud. This algorithm is less scale dependent than several commonly used roughness calculations. The results of this study show that TLSs can be used for multitemporal scanning of large surfaces and that small changes in surface elevation and roughness can be detected. Statistical analysis of the observed changes against terrain indices did not yield significant evidence for process differentiation.
Authors
Robert BarneveldAbstract
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Assessing redox conditions in soil and groundwater is challenging because redox reactions are oxygen sensitive, hence, destructive sampling methods may provide contact with air and influence the redox state. Furthermore, commonly used redox potential sensors provide only point measurements and are prone to error. This paper assesses whether combining electrical resistivity (ER) and self-potential (SP) measurements can allow the mapping of zones affected by anaerobic degradation. We use ER imaging because anaerobic degradation can release iron and manganese ions, which decreases pore water resistivity, and produces gas, which increases resistivity. Also, electrochemical differences between anaerobic and aerobic zones may create an electron flow, forming a self-potential anomaly. In this laboratory study, with four sand tanks with constant water table heights, time-lapse ER and SP mapped changes in electrical/electron flow properties due to organic contaminant (propylene glycol) degradation. Sampled pore water mapped degradation and water chemistry. When iron and manganese oxides were available, degradation reduced resistivity, because of cation release in pore water. When iron and manganese oxides were unavailable, resistivity increased, plausibly from methane production, which reduced water saturation. To bypass the reactions producing methane and release of metallic cations, a metal pipe was installed in the sand tanks between anaerobic and aerobic zones. The degradation creates an electron surplus at the anaerobic degradation site. The metal pipe allowed electron flow from the anaerobic degradation site to the oxygen-rich near surface. The electrical current sent through the metal pipe formed an SP anomaly observable on the surface of the sand tank. Time-lapse ER demonstrates potential for mapping degradation zones under anaerobic conditions. When an electrical conductor bridges the anaerobic zone with the near surface, the electron flow causes an SP anomaly on the surface. However, electrochemical differences between anaerobic and aerobic zones alone produced no SP signal. Despite their limitations, ER and SP are promising tools for monitoring redox sensitive conditions in unsaturated sandy soils but should not be used in isolation.
Authors
Trine Eggen Heidi Amlund Aksel Bernhoft Ole Martin Eklo Gunnar Sundstøl Eriksen Belinda Eline Flem Torsten Källqvist Bal Ram Singh Eiliv Steinnes Stefan Trapp Anne Falk Øgaard Christiane Kruse Fæste Erik-Jan Lock Live Lingaas Nesse Einar Ringø Håvard Steinshamn Robin Ørnsrud Åshild KrogdahlAbstract
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Authors
Robert Barneveld Sjoerd E.A.T.M. van der Zee Inga Greipsland Sigrun Hjalmarsdottir Kværnø Jannes StolteAbstract
Measures designed to control erosion serve two purposes: on site (reduce soil loss) and off site (reduce sediment delivery to streams and lakes). While these objectives often coincide or at least are complementary, they could result in different priority areas when spatial planning is concerned. Prioritising for soil loss reduction at the field level will single out areas with high erosion risk. When sediment flux at the catchment scale is concerned, sediment pathways need to be identified in ex ante analyses of soil conservation plans. In Norway, different subsidy schemes are in place to reduce the influx of solutes and sediments to the freshwater system. Financial support is given to agronomic measures, the most important of which is reduced autumn tillage where areas with higher erosion risk receive higher subsidies. The objectives of this study are (1) to assess the use of an index of connectivity to estimate specific sediment yields, and (2) to test whether conservation measures taken in critical source areas are more effective than those taken at where erosion risk levels are the highest. Different modelling approaches are combined to assess soil loss at catchment level from sheet and gully erosion and soil losses through the drainage system. A calibration on two parameters gave reasonable results for annual soil loss. This model calibration was then used to quantify the effectiveness of three strategies for spatial prioritisation: according to hydrological connectivity, sheet erosion risk level and estimated specific sediment yield. The latter two strategies resulted in a maximum reduction in total soil loss due to reduced autumn tillage of 10%. Both model performance and the effectiveness of the different prioritisation strategies varied between the study catchments.