Analysis of inorganic nitrogen leaching in a boreal river basin in northern Finland

In this study the dynamic, semi-distributed INCA-N model was applied to the boreal Simojoki river basin in northern Finland to outline inorganic nitrogen (N) leaching patterns and N processes in catchment scale. Special emphasis was paid to the quality assurance of the modelling work. The dominant human impacts in the area are forestry, agriculture, scattered settlement and atmospheric deposition. In order to assess the effectiveness of current environmental policies and to implement river basin management plans, it is essential to know the relative significance of the different sources of pollution. INCA-N explained main features of the hydrological pattern and seasonality of inorganic N concentrations in river water when N processes in soil in sub-zero temperatures were included. Over-winter N mineralization processes in soil accounted for 38% of annual N mineralization. The lowest concentrations during the growing season were not reproduced, which indicates that there are some retention processes missing from the model. As summer is typically a low flow period the simulation results are reliable as long as the interpretation is based on daily or annual loads. Loading from the river basin was mostly dependent on annual hydrology and it was concentrated to peaks during the snow melting period. In the upper parts of the river inorganic N load originated mainly from commercial forests. At the outlet of the river anthropogenic sources accounted for more than half of the overall inorganic N load, with agriculture, forestry and scattered settlements making almost equal contributions. Expected changes in atmospheric N deposition would not have any significant effect but the combination of water protection measures both in agricultural and forestry areas and in scattered settlement areas would decrease inorganic N load by 18% of the total load. The expected increase in forest felling of 20% would not have an influence, but increase in agricultural land due to the EU's Common Agricultural Policy might lead to increased N load to the sea.reviewe

Modelling of water balance and nitrogen cycle in vegetative filter strips

The retention of nutrients by 10-m-wide grass buffers and buffers under natural vegetation has been studied over 10 years in Jokioinen in southwestern Finland. The results have been compared with those from 70-m-long plots without buffers. Grass was sown on the adjacent field and plots without buffers in 2002, and the field plots and these were grazed for 12 and 24 days in summer 2003 and 2004, respectively

Simulated nitrogen leaching, nitrogen mass field balances and their correlation on four farms in south-western Finland during the period 2000-2005

Nitrogen (N) gross balance is one of the indicators designed for following developments in agriculture in the European Union. A nutrient surplus occurs when the quantity of a nutrient applied in fertilizers is greater than that removed during harvest. In this study the usefulness of N balance in studying the fate of N and controlling N leaching from agricultural fields in south-western Finland was evaluated. To estimate N leaching in 2000–2005 the mathematical, process-based model COUP was applied to twelve fields representing four agricultural production sectors. The fields represented conventional cereal production, organic cereal production and both conventional cattle and pig husbandry. Simulated N leaching was lowest from cereal production fields with a low N balance. Higher N leaching from pig and cattle production farms might be reduced by decreasing the N balance but also by applying manure in spring instead of autumn. Both N balance and simulated N leaching from organic farm were relatively high compared to low N application rate to the fields. N balance appears to be a rather useful indicator of N leaching over longer periods of time. In the short term, N leaching depends mainly on precipitation and on cultivation practices, like timing and amount of fertilizer application. Statistical evaluation indicated significant positive correlation between calculated N balance and simulated N leaching, especially when supported by constant values of precipitation and N mineralization rate. Decrease of N balance by 1 kg ha–1yr–1 decreased N leaching by 0.3 kg ha–1yr–1. High positive N balances are conducive to abundant accumulation of residual N in soil and consequently to a high risk of N leaching during rainy seasons

Testing the INCA model in a small agricultural catchment in southern Finland

International audienceNutrient leaching from agricultural production is still recognised as a major environmental problem in Finland. To estimate agricultural nitrogen loading under changing land-use and climate conditions, the Integrated Nitrogen Model for Catchments (INCA) was applied in Savijoki, a small (15.4 km2) agricultural catchment, which represents the intensively cultivated areas in south-western Finland. Hydrological calibration and testing of the INCA model was first carried out in Savijoki during 1981?2000. In spite of heterogeneous soil and land-use conditions, INCA was able to reproduce the overall hydrological regime in the stream. The model was calibrated further in respect of nitrogen processes during 1995?2000. The model was able, reasonably well, to simulate the overall annual dynamics of the inorganic N concentrations in the stream water and the annual N export from the catchment. The average simulated NO3-N export was 550 kg N km?2 yr?1 and the observed one (constituting more than half of the annual total N export) was 592 kg N km?2 yr?1. For NH4-N, the simulated export was somewhat higher than that measured but NH4-N was only 4% of the total N export. In spite of some underestimation of flow and N concentration during extreme hydrological conditions, the INCA model proved to be a useful tool for analysing flow pattern and inorganic nitrogen leaching in a small agricultural catchment, characterised by a rapid response to rainfall. Keywords: nitrogen, integrated modelling, hydrology, catchment, agricultur

Buffer strips as filters for nutrients from grazed lands and nutrient cycling on the buffer strips

The retention of agricultural nitrogen and phosphorus by 10-m-wide grass buffer strips and buffers under natural vegetation has been studied for ten years on an experimental field at Jokioinen

Modelling of vegetative filter strips in catchment scale erosion control

Tämän työn tarkoituksena oli kehittää käytännöllinen menetelmä herkästi erodoituvien peltoalueiden kartoittamiseksi, eli niiden alueiden, jotka ovat optimaalisia paikkoja suojakaistoille. Samalla arvioitiin myös suojakaistojen tehokkuutta eroosion torjunnassa. Tutkimusalueiksi valittiin kaksi valuma-aluetta eri puolilta Suomea. Helposti erodoituvat alueet arvioitiin paikkatietojärjestelmällä yhdistämällä tiedot maalajista, maan käytöstä ja pellon kaltevuudesta. Suojakaistojen tehokkuutta arvioitiin ICECREAM-mallilla, joka on Suomen oloihin sovellettu versio CREAMS-mallista. Mallinnus tehtiin ilman suojakaistoja sekä lisäämällä peltoon 1 m, 3 m ja 15 m leveät suojakaistat. Ilman suojakaistoja tehtyjen malliajojen perusteella eroosion määrä riippuu lähinnä pellon kaltevuudesta. Maalajilla on suurempi vaikutus eroosion määrään kuin kasvilla. Suojakaistojen tehokkuudet vaihtelivat suuresti eri tilanteissa. Malliajojen tulokset yhdistettiin paikkatietojärjestelmään ja tulokseksi saatiin, että valuma-aluetasolla suojakaistojen teho eroosion vähentämisessä ojiin rajautuvilta pelloilta oli 50-89 %. Paikkatietojärjestelmään perustuvaa suojakaistojen paikan arviointia verrattiin kenttätutkimukseen, joka oli tehty toisella valuma-alueella. Molemmilla menetelmillä löydettiin ne alueet, joilta eroosio on suurinta, mutta menetelmien yhdistelmällä päästiin parhaaseen lopputulokseen.The efficiency of vegetative filter strips to reduce erosion was assessed by simulation modelling in two catchments located in different parts of Finland. The areas of high erosion risk were identified by a Geographical Information System (GIS) combining digital spatial data of soil type, land use and field slopes. The efficiency of vegetative filter strips (VFS) was assessed by the ICECREAM model, a derivative of the CREAMS model which has been modified and adapted for Finnish conditions. The simulation runs were performed without the filter strips and with strips of 1 m, 3 m and 15 m width. Four soil types and two crops (spring barley, winter wheat) were studied. The model assessments for fields without VFS showed that the amount of erosion is clearly dominated by slope gradient. The soil texture had a greater impact on erosion than the crop. The impact of the VFS on erosion reduction was highly variable. These model results were scaled up by combining them to the digital spatial data. The simulated efficiency of the VFS in erosion control in the whole catchment varied from 50 to 89%. A GIS-based erosion risk map of the other study catchment and an identification carried out by manual study using topographical paper maps were evaluated and validated by ground truthing. Both methods were able to identify major erosion risk areas, i.e areas where VFS are particularly necessary. A combination of the GIS and the field method gives the best outcome.vokValuma-aluetason mallisovellus suojakaistojen käytöstä eroosion torjunnass

Influence of EU policy on agricultural nutrient losses and the state of receiving surface waters in Finland

In Finland, the first large-scale efforts to control nutrient loading from agriculture got under way with the introduction of the EU Agri-Environmental Program in 1995. We examined whether these efforts have decreased agricultural nutrient losses and improved the quality of receiving waters. To do so we used monitoring data on fluxes of nutrients and total suspended solids in agricultural catchments in 1990–2004 and on the water quality of agriculturally loaded rivers, lakes and estuaries in 1990–2005. No clear reduction in loading or improvement in water quality was detected. Hydrological fluctuations do not seem to have eclipsed the effects of the measures taken, since there was no systematic pattern in runoff in the period studied. The apparent inefficiency of the measures taken may be due to the large nutrient reserves of the soil, which slowed down nutrient reductions within the period studied. Simultaneous changes in agricultural production (e.g. regional specialisation) and in climate may also have counteracted the effects of agri-environmental measures. The actions to reduce agricultural loading might have been more successful had they focused specifically on the areas and actions that contribute most to the current loading

Modelling impacts of climate and deposition changes on nitrogen fluxes in northern catchments of Norway and Finland

International audienceThe Integrated Nitrogen model for Catchments (INCA) was applied to three upland catchments in Norway and Finland to assess the possible impacts of climate change and nitrogen (N) deposition on concentrations and fluxes of N in streamwater in cold regions of Europe. The study sites cover gradients in climate and N deposition from the southern boreal Øygard Brook (2.6 km2) in SW Norway, via the southern/middle boreal Simojoki River (3610 km2) in northern Finland to the sub-arctic Dalelva Brook (3.2 km2) in northern Norway. The INCA scenario simulations included future N deposition scenarios (current legislation and maximum feasible reduction) and climate scenarios for 2050 (ECHAM4/OPYC3; HadCM3) treated separately and in combination. As a result of climate change, the INCA model predicted markedly reduced duration and amounts of snow cover in all catchments. The occurrence of winter rainfall and melting periods was predicted to become more frequent so that more frequent floods in winter will to a large extent replace the regular snowmelt flood in spring. At the northernmost catchment, Dalelva, the predicted temperature increase might result in a doubling of the net mineralisation rate, thereby greatly increasing the amount of available inorganic N. At all catchments, the increased N supply was predicted to be largely balanced by a corresponding increase in N retention, and relatively small increases in NO3- leaching rates were predicted. This dynamic relationship is, however, strongly dependent on the temperature responses of the key N transformation processes modelled. A future reduction in N emissions and deposition, as agreed under current legislation, would have pronounced effects on concentrations of NO3- in streamwater at the southernmost catchment, Øygard, even following a climate change around 2050. At the more remote Dalelva and Simojoki catchments, the N emission reductions will be small compared to the internal N recycling processes, and climate change will to a large extent offset the effects of reduced N deposition. Keywords: catchments, surface water, scenarios, climate, hydrology, nitrogen deposition, nitrate leachin

Jäljitettävyyttä ja vastuullisuutta palvelevan elinkaaripohjaisen ympäristötiedon hallintamallin määrittely ja käytön kehittäminen elintarvikeketjussa

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Adaptation to Climate Change by Agri-Environmental Policy in Finland

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