Nitrogen Reduction Measures Research Articles

Discordance between farmers and scientists - Perspectives on nitrogen reduction measures in Denmark

Mitigating nitrogen leaching from agricultural land is imperative for enhancing the ecological status of aquatic ecosystems. Incorporating the knowledge and perceptions of farmers regarding the feasibility and effectiveness of implementing nitrogen reduction measures is vital for increasing the adoption rate of such measures and related policies. Concurrently, the insights and perspectives of scientists advising policymakers on the implementation of these measures can facilitate a more comprehensive understanding of the barriers and potential for implementation. In this study, we employ Q methodology to elucidate the opinions of 11 farmers and 14 key scientists involved in providing contractual science policy advice to Danish ministries on nitrogen reduction measures. Results show that across the perspectives of farmers and scientists, four main factors (viewpoints) can be identified: ‘Evidence-driven viewpoints’, ‘On-farm efficiency-driven viewpoints’, ‘Hydrological and landscape-scale viewpoints’, ‘Innovation-based viewpoints. From this, we suggest that within the field of nitrogen mitigation and implementation, there is a general broad division and opposing perspectives between scientists and farmers. The evidence presented here shows that scientists’ viewpoints do not correspond to the viewpoints of farmers in most cases. Scientists broadly believe that landscape and long-term measures, especially wetlands, are most effective nitrogen measures, according to scientific evidence. This clashes severely with some farmer participants, who strongly believe that there should be more personal freedom and flexibility to make individual farm level management choices. This is a significant barrier to the uptake of the best possible measures.

Cost effectiveness, nitrogen, and phosphorus removal in field-based woodchip bioreactors treating agricultural drainage water

Nitrogen (N) and phosphorus (P) losses to surface and coastal waters are still critically high across Europe and globally. Measures to mitigate and reduce these losses are being implemented both at the cultivated land surface and at the edge-of-fields. Woodchip bioreactors represent a new alternative in Denmark for treating agricultural drainage water, and the present study—based on two years of data from five Danish field-based bioreactors—determined N removal rates varying from 1.49 to 5.37 g N m−3 d−1 and a mean across all bioreactors and years of 2.90 g N m−3 d−1. The loss of phosphorus was relatively high the first year after bioreactor establishment with rates varying from 298.4 to 890.8 mg P m−3 d−1, but in the second year, the rates ranged from 12.2 to 77.2 mg P m−3 d−1. The investments and the costs of the bioreactors were larger than expected based on Danish standard investments. The cost efficiency analysis found the key issues to be the need for larger investments in the bioreactor itself combined with higher advisory costs. For the four woodchip bioreactors considered in the cost efficiency analysis, the N removal cost was around DKK 350 per kg N ($50 per kg N), which is ca. 50% higher than the standard costs defined by the Danish authorities. Based on the estimated costs of the four bioreactor facilities included in this analysis, a bioreactor is one of the most expensive nitrogen reduction measures compared to other mitigation tools.

Impact of agriculture and land use on nitrate contamination in groundwater and running waters in central-west Poland.

Protected areas due to their long-term protection are expected to be characterized by good water quality. However, in catchments where arable fields dominate, the impact of agriculture on water pollution is still problematic. In Poland, recently, the fertilization level has decreased, mostly for economic reasons. However, this applies primarily to phosphorus and potassium. In order to evaluate the impact of agriculture on water quality in a protected area with a high proportion of arable fields in the aspect of level and type of fertilization, complex monitoring has been applied. The present study was carried out in Wielkopolska National Park and its buffer zone, which are protected under Natura 2000 as Special Areas of Conservation and Special Protection Areas. The aim of the study were (1) to assess the impact of agriculture, with special attention on fertilization, on groundwater, and running water quality and (2) to designate priority areas for implementing nitrogen reduction measures in special attention on protected areas. In our study, high nitrogen concentrations in groundwater and surface waters were detected in the agricultural catchments. The results demonstrate that in the watersheds dominated by arable fields, high nitrogen concentrations in groundwater were measured in comparison to forestry catchments, where high ammonium concentrations were observed. The highest nitrogen concentrations were noted in spring after winter freezing, with a small cover of vegetation, and in the areas with a high level of nitrogen application. In the studied areas, both in the park and its buffer zone, unfavorable N:P and N:K ratios in supplied nutrients were detected. Severe shortage of phosphorus and potassium in applied fertilizers is one of the major factors causing leaching of nitrogen due to limited possibilities of its consumption by plants.

Determination of nitrogen reduction levels necessary to reach groundwater quality targets in Slovenia

Within a collaborative project between Slovenian Environment Agency (ARSO) and Research Center Jülich (FZJ), nitrogen reduction levels necessary to reach groundwater quality targets in Slovenia were assessed. For this purpose the hydrological model GROWA–DENUZ was coupled with agricultural N balances and applied consistently to the whole territory of Slovenia in a spatial resolution of 100×100m. GROWA was used to determine the water balance in Slovenia for the hydrologic period 1971–2000. Simultaneously, the displaceable N load in soil was assessed from agricultural Slovenian N surpluses for 2011 and the atmospheric N deposition. Subsequently, the DENUZ model was used to assess the nitrate degradation in soil and, in combination with the percolation water rates from the GROWA model, to determine nitrate concentration in the leachate. The areas showing predicted nitrate concentrations in the leachate above the EU groundwater quality standard of 50mg NO3−/L have been identified as priority areas for implementing nitrogen reduction measures. For these “hot spot” areas DENUZ was used in a backward mode to quantify the maximal permissible nitrogen surplus levels in agriculture to guarantee a nitrate concentration in percolation water below 50mg NO3−/L. Model results indicate that additional N reduction measures should be implemented in priority areas rather than area-covering. Research work will directly support the implementation of the European Union Water Framework Directive in Slovenia, e.g., by using the maximal permissible nitrogen surplus levels as a framework for the derivation of regionally adapted and hence effective nitrogen reduction measures.

A Bayesian changepoint–threshold model to examine the effect of TMDL implementation on the flow–nitrogen concentration relationship in the Neuse River basin

In-stream nutrient concentrations are well known to exhibit a strong relationship with river flow. The use of flow measurements to predict nutrient concentrations and subsequently nutrient loads is common in water quality modeling. Nevertheless, most adopted models assume that the relationship between flow and concentration is fixed across time as well as across different flow regimes. In this study, we developed a Bayesian changepoint–threshold model that relaxes these constraints and allows for the identification and quantification of any changes in the underlying flow–concentration relationship across time. The results from our study support the occurrence of a changepoint in time around the year 1999, which coincided with the period of implementing nitrogen control measures as part of the TMDL program developed for the Neuse Estuary in North Carolina. The occurrence of the changepoint challenges the underlying assumption of temporal invariance in the flow–concentrations relationship. The model results also point towards a transition in the river nitrogen delivery system from a point source dominated loading system towards a more complicated nonlinear system, where non-point source nutrient delivery plays a major role. Moreover, we use the developed model to assess the effectiveness of the nitrogen reduction measures in achieving a 30% drop in loading. The results indicate that while there is a strong evidence of a load reduction, there still remains a high level of uncertainty associated with the mean nitrogen load reduction. We show that the level of uncertainty around the estimated load reduction is not random but is flow related.

Determination of nitrogen reduction levels necessary to reach groundwater quality targets in large river basins: the Weser basin case study, Germany

We used the interdisciplinary model network REGFLUD to predict the actual mean nitrate concentration in percolation water at the scale of the Weser river basin (Germany) using an area—differentiated (100 m × 100 m) approach. REGFLUD combines the agro-economic model RAUMIS for estimating nitrogen surpluses and the hydrological models GROWA/DENUZ for assessing the nitrate leaching from the soil. The areas showing predicted nitrate concentrations in percolation water above the EU groundwater quality standard of 50 mg NO3/l, have been identified as priority areas for implementing nitrogen reduction measures. For these “hot spot” areas a backward modelling approach was used to quantify the maximal permissible nitrogen surplus levels in agriculture to guarantee a mean long-term nitrate concentration in percolation water below 50 mg NO3/l. Research work will directly support the implementation of the EU-Water Framework Directive in the Weser basin, e.g. by using the maximal permissible nitrogen surplus levels as a framework for the derivation of regionally adapted and hence effective nitrogen reduction measures.

Planning and implementation of nitrogen reduction measures in catchment areas based on a determination and ranking of target areas

The implementation schedule for the EU water framework directive requires the creation of monitoring programmes for water bodies according to the intensity of the pollution risk by the end of 2006. Until 2009 river basin district management programmes have to be established followed by the implementation of measures from the management plans (until 2012). The WAgriCo-project (Water Resources Management in Cooperation with Agriculture), is a collaborative project funded by the European Commission Life Fund within the period October 2005 to September 2008, involving six British and four German institutions. The WAgriCo-project is based around the catchment management process, of identifying diffuse pollution issues and potential management solutions, involving land managers/advisors to implement methods and to assess their effectiveness in terms of pollution reduction and costs. For a basic understanding of the interactions between these issues an integrated hydrological/hydrogeological conceptual model has been set up. The model consists of three main features: natural characteristic assessment, anthropogenic impact assessment using monitoring data and model tools providing a linkage between the first two parts. In this paper the application of the integrated hydrological/hydrogeological conceptual model for geographical prioritization and determination of environmental target areas in the case study area Große Aue in the Federal State of Lower Saxony, Germany is described and discussed. It is demonstrated how area differentiated parameters like the denitrification condition in soils, the runoff ratio, nitrate concentrations in the leachate and groundwater monitoring data are determined and combined in order to determine target areas. With the given example of the case study area Grosse Aue, the importance of defining the receptor of nitrate outputs (groundwater or surface water) and the environmental target prior to the delineation of environmental target areas could be shown.

Critical N:P ratio for cyanobacteria and N2-fixing species in the large shallow temperate lakes Peipsi and Võrtsjärv, North-East Europe

In the 1990s a sharp decrease in nitrogen loading occurred in Estonian rivers, bringing about a reduction of the nitrogen-to-phosphorus ratio (N:P ratio) in the large shallow lakes, Peipsi (3,555 km2, mean depth 7.1 m) and Vortsjarv (270 km2, 2.8 m). The average mass ratio of total nitrogen (TN) and total phosphorus (TP) in Vortsjarv (45) was about twice as high as that in Peipsi (22). In Peipsi, the N2- fixing Gloeotrichia echinulata, Aphanizomenon flosaquae and Anabaena species prevailed in the summer phytoplankton, while in Vortsjarv the dominant cyanobacteria were Limnothrix planktonica, L. redekei and Planktolyngbya limnetica, which cannot fix N2; the main N2-fixing taxa Aphanizomenon skujae and Anabaena sp. seldom gained dominance. In May-October the critical TN:TP mass ratio, below which N2-fixing cyanobacteria (Nfix) achieved high biomasses, was ∼40 in Vortsjarv and ∼30 in Peipsi. The percentages of both total cyanobacteria (CY) and Nfix (CY% and Nfix%) in Peipsi achieved their maximum values at an N:P mass ratio at or below 20 for both TN:TP and Nmin:SRP. In Vortsjarv, the TN:TP supporting a high Nfix% was between 30 and 40 and the Nmin:SRP supporting this high percentage was in the same range as that in Peipsi (<20), though the maximum Nfix% values in Vortsjarv (69%) were much lower than in Peipsi (96%). The Nmin:SRP ratio explained 77% of the variability in Nfix% in May–October. The temperature dependence of Nfix% approximated to the maximum function type, with an upper limiting value at a certain water temperature, and this was most distinct in May–October. The critical TN:TP ratios obtained from our study (roughly 30 for Peipsi and 40 for Vortsjarv) are much higher than the Redfield N:P mass ratio routinely considered (7). Our results represent valuable guidelines for creating effective management strategies for large shallow lakes. They provide a basis for stressing the urgent need to decrease phosphorus loading and to keep the in-lake P concentration low, and not to implement nitrogen reduction measures without a simultaneous decrease of phosphorus concentration.

Determination and ranking of target areas in catchments for the implementation of nitrogen reduction measures

Abstract. The implementation of the EU Water Framework Directive (EU-WFD) forms the background of the WAgriCo-project (Water Resources Management in Cooperation with Agriculture). WagriCo concentrates on the development of nitrogen management options adapted to hydrological and agro-economic site conditions and at demonstrating new participation approaches and technologies suitable for setting-up programmes of measures. The article outlines the conceptual model approach and its application in the pilot region "Große Aue" (Northern Germany). Furthermore the process of delineating priority areas is described, which act as spatial targets for the adaptation of regionally differentiated nutrient reduction measures.

Water fluxes and diffuse nitrate pollution at river basin scale: coupling of agro-economic models and hydrological approaches

An integrated model system has been developed to estimate the impact of nitrogen reduction measures on the nitrogen load in groundwater and in river catchment areas. The focus lies on an area-wide, regionally differentiated, consistent link-up between the indicator "nitrogen balance surplus" and nitrogen charges into surface waters. As a starting point of the analysis actual nitrogen surpluses in the soil were quantified using the agro-economic RAUMIS-model, which considers the most important N-inputs to the soil and N-removals from the soil through crop harvest. The most important pathways for diffuse nitrogen inputs into river systems are modelled with the water balance model GROWA. Additionally, the time-dependent nitrogen degradation along the nitrogen pathways in soil and groundwater are modelled using the WEKU-model. The two selected river basins in Germany cover a variety of landscape units with different hydrological, hydrogeological and socio-economic characteristics. The results indicate a wide range of annual nitrogen surpluses for the rural areas between than 10 kg N ha(-1) x a(-1) and 200 kg N ha(-1) x a(-1) or more, depending on the type and intensity of farming. The level of nitrogen inputs into the surface waters is reduced because of degradation processes during transport in soil and groundwater. Policy impact analyses for a nitrogen tax and a limitation of the livestock density stress the importance of regionally adjusted measures.

Management of regional German river catchments (REGFLUD) impact of nitrogen reduction measures on the nitrogen load in the River Ems and the River Rhine

The REGFLUD-project, commissioned by Germany's Federal Research Ministry (BMBF), addresses the problem of reducing diffuse pollution from agricultural production. The objective of the project is the development and application of multi-criteria scientific methods, which are able to predict diffuse pollution in river basins subject to economic feasibility and social acceptability. The selected river basins (Ems and Rhine basins) cover a variety of landscape units with different hydrological, hydrogeological and socio-economic characteristics. This paper focuses on the analysis of the effects of certain policy measures to reduce diffuse pollution by nitrogen. For this purpose a model system consisting of an agricultural sector model, a water balance model and a residence time/denitrification model was developed and applied. First results indicate a wide range of annual nitrogen surpluses for the rural areas between less than 10 kg N/ha up to 200 kg N/ha or more depending on the type and intensity of farming. Compared to the level of nitrogen surpluses the level of nitrogen inputs into the surface waters is relatively moderate because of degradation processes during transport in soil and groundwater. Policy impact analysis for a nitrogen tax and a limitation of the livestock density stress the importance of regionally tailored measures.

Impact of nitrogen reduction measures on the nitrogen loads of the river Ems and Rhine (Germany)

The REGFLUD-project, commissioned by Germany’s Federal Research Ministry (BMBF), addresses the problem of reducing diffuse pollution from agricultural production. The objective of the project is the development and application of multi-criteria scientific methods, which are able to predict diffuse pollution in river basins subject to economic feasibility and social acceptability. The selected river basins (the entire Ems basin and sub-catchments of the Rhine) cover a variety of landscape units with different hydrological, hydrogeological and socio-economic characteristics. This paper focuses on the analysis of the effects of certain policy measures to reduce diffuse pollution by nitrogen. For this purpose, a model system consisting of an agricultural sector model, a water balance model and a residence time/denitrification model was combined and applied. First results indicate a wide range of annual nitrogen surpluses for the rural areas between less than 10 N ha −1 a −1 up 200 kg N ha −1 a −1, or more depending on the type and intensity of farming. Compared to the level of nitrogen surpluses the level of nitrogen inputs into the surface waters is relatively moderate because of degradation processes during transport in soil and groundwater. Policy impact analyses for a nitrogen tax and a limitation of the livestock density stress the importance of regionally adjusted measures.

Model based impact analysis of policy options aiming at reducing diffuse pollution by agriculture—a case study for the river Ems and a sub-catchment of the Rhine

In this paper an integration of the agricultural economic model RAUMIS with the hydrological models GROWA98 and WEKU is presented. The focus lies on an area wide, regionally differentiated, consistent link-up between the indicator “nitrogen balance surplus” and nitrogen charges into surface waters. The model network is used to analyze the status quo situation in the year 1999 for two river catchments in Germany that feature very distinct natural and socio-economic conditions. Regarding agriculture, the study areas include regions with specializations in cash crops, in intensive livestock featuring high nitrogen surplus, and extensive livestock production on permanent grassland. Due to regionally varying hydrological conditions quite different shares of agricultural nitrogen surpluses ranging from 25 to 92% enter surface waters. Furthermore, impacts of alternative nitrogen reduction measures namely a limitation of livestock density and a tax on mineral nitrogen are quantified. Measures of the nitrogen reduction potential and costs in terms of agricultural income forgone are taken into account in the assessment. Results regarding the effects of restricting the livestock density or tax mineral nitrogen highlight that the mitigation of diffuse water pollution problems requires regionally tailored measures.

Impact of nitrogen reduction measures on nitrogen surplus, income and production of German agriculture

Among the numerous non-point sources of diffuse water pollution with nitrogen, agriculture is counted one of the main sources. The agricultural policies of the Agenda 2000 and a decoupling of direct payments for farmers from their production decisions are exemplarily evaluated as nitrogen reduction measures using the Regional Agricultural and Environmental Information System RAUMIS. The results show that until the target year 2010 the risk of diffuse pollution of water bodies with nitrogen is a regional problem in Germany. These problems are neither mitigated by the policies of Agenda 2000 nor by a decoupling of direct payments from production decisions of farmers. While total nitrogen surplus reduces considerably after a decoupling of direct payments due to decreases of land-use the nitrogen surplus on the remaining cultivated area increases resulting from structural changes. Granting the same amount of direct payments to farmers in both policy alternatives the agricultural sector income would be higher after a decoupling of direct payments opposed to the Agenda 2000 resulting from a more efficient allocation of inputs.

Comprehensive cost-effectiveness analysis of measures to reduce nitrogen emissions in Switzerland

This paper proposes a comprehensive cost-effectiveness analysis to evaluate environmental policies. While effectiveness is measured as the reduction of different pollutants aggregated to a damage index, all the other effects apart from pollutant reduction are monetarised and expressed as cost. The damage index is based on the ‘Umwelt-Belastungs-Punkte’ (UBP)-method (Environmental Impact Points) and is extended to include the different geographical ranges of various pollutants. The method is then applied to assess the cost-effectiveness of nitrogen reduction measures in Switzerland. The results indicate that a less nitrogen-intensive agricultural production and the use of a new generation of low nitrogen oxide burners are very cost-effective.

The monitoring of nitrogen surpluses from agriculture

Nitrogen balances are calculated as a tool for monitoring national and regional losses of nitrogen to the environment. In the Netherlands 70% of the nitrogen losses occur in agriculture; mainly (70%) in soil and groundwater. Where measurements on emissions to the different environmental media are laborious and costly, calculations are made with models or statistics. This paper describes two methods to determine the total nitrogen surpluses from agriculture using statistical information: the farmgate and the soil surface method. Surpluses are defined as the difference between the nitrogen inputs into and outputs from the agricultural system. The methods described are used to monitor the effectiveness of nitrogen reduction measures taken on account of the EU Nitrate Directive and the OSPARCOM agreements. The methods of calculation described here are also used by OECD and EUROSTAT to compute indicators of nutrient use. Results from the Netherlands over a ten-year period indicate that so far little progress has been made in reducing nitrogen surpluses. Ammonia emissions have been reduced at the expense of an increased loss of nitrogen to the soil. Estimating nitrogen surpluses calculated as the difference between the inputs of nitrogen to the soil and the withdrawal by crops (soil surface method) requires consistent data on the feed-animal-manure balance. When comparing data on agricultural surpluses between different countries this consistency is a major concern.