Estimated N leaching losses for organic and conventional farming in Denmark

The impact of organic compared to conventional farming practices on N leaching loss was studied for Danish mixed dairy and arable farms using an N balance approach based on representative data. On mixed dairy farms a simple N balance method was used to estimate N surplus and N leaching loss. On arable farms the simple N balance method was unreliable due to changes in the soil N pool. Consequently, the FASSET simulation model was used to estimate N surplus, N leaching loss and the changes in the soil N pool. The study found a lower N leaching loss from organic than conventional mixed dairy farms, primarily due to lower N inputs. On organic arable farms the soil N pool was increasing over years but the N leaching loss was comparable to conventional arable farms. The soil N pool was primarily increased by organic farming practices and incorporation of straw. The highest increase in the soil N pool was seen on soils with a low level of soil organic matter. The level of N leaching loss was dependent on soil type, the use of catch crops and the level of soil organic matter, whereas incorporation of straw had a minor effect. N leaching was highest on sandy soils with a high level of soil organic matter and no catch crops. The study stresses the importance of using representative data of organic and conventional farming practices in comparative studies of N leaching loss

Impact of organic pig production systems on CO2 emission, C sequestration and nitrate pollution

Organic rules for grazing and access to outdoor area in pig production may be met in different ways, which express compromises between considerations for animal welfare, feed self-reliance and negative environmental impact such as greeehouse gas emissions and nitrate pollution. This article compares environmental impact of the main organic pig systems in Denmark. Normally sows are kept in huts on grassland and finishing pigs are being raised in stables with access to an outdoor run. One alternative practised is rearing also the fattening pigs on grassland all year round. The third method investigated was a one-unit pen system mainly consisting of a deep litter area under a climate tent and with restricted access to a grazing area. Using life cycle assessment (LCA) methodology, the emissions of greenhouse gasses of the all free range system was estimated to be 3.3 kg CO2-equivalents kg-1 liveweight pig, which was significantly higher than the indoor fattening system and the tent system yeilding 2.9 and 2.8 kg CO2-eq. kg-1 pig respectively. This was 7-22% higher compared with Danish conventional pig production but, due to the integration of grass-clover in the organic crop rotations these had an estimated net soil carbon sequestration. When carbon sequestration was included in the LCA then the organic systems had lower green house gas emissions compared with the conventional pig production. Eutrophication in nitrate equivalents per kg pig was 21-65% higher in the organic pig systems and acidification was 35-45% higher per kg organic pig compared with the conventional system. We conclude that even though the all free range system theoretically has agro-ecological advantages over the indoor fattening system and the tent system due to a larger grass-clover area this potential is difficult to implement in practice due to problems with leaching on sandy soil. Only if forage can contribute a larger proportion of the pigfeed-uptake may the free range system be economically and environmentally competitive. Improvement of nitrogen cycling and efficiency is the most important factor for reducing the overall environmental load from organic pig meat. Presently a system with pig fattening in stables and concrete covered outdoor runs seems to be the best solution from an environmental point of view

Simulation of nitrate leaching from an organic dairy crop rotation with different manure types and loads

Introduction Management of nitrogen in dairy systems is especially difficult due to the use of organic manures and the residual effects of the pasture. During grazing a considerable build-up of soil N is often observed. Ploughing of the grassland is therefore followed by a large mineralization that might exceed the demand of the subsequent crop. This might lead to large amount of nitrate being leached. In addition, rotations dependent on organic manures rather than mineral fertilizers are believed to have a higher risk of nitrate leaching. The study present results from simulations with the FASSET model (Berntsen et al., 2003) of nitrate leaching and crop growth in organic dairy systems with two types of manures at two different stocking levels. Method The experiment was established at Foulum, Denmark in 1994 (Eriksen et al. 1999) and had a six-year crop rotation (barley- grass/clover – grass/clover – barley/pea – winter wheat – fodder beet). The grass/clover was grazed by cattle. The four treatments were: two types of manures (slurry and a mixture a deep litter and slurry) at two different levels. These levels correspond to livestock densities of 0.9 and 1.4 livestock units ha-1. The FASSET model was used to simulate the above experiment. The model is a whole farm that contains a crop-soil-atmosphere model, which simulates daily changes in crop growth, soil organic matter and transport of several solutes. The soil organic matter model is based on Petersen et al. (2003). The model simulated all the different treatments in the years 1993 to 2002 using observed management, measured manure application and composition, measured climate data and soil characteristics. Table 1 shows the simulated and observed N input, N harvested and N leached. Both simulations and measurements indicate that the effects of the different types of organic input are small and the effect of the level of input are between 3-7 kg-N/ha. The crops had different leaching potential. Winter wheat had the highest simulated nitrate leaching followed by barley/pea mixture, oat, spring barley, beets and grass-clover. A similar crop ranking was observed in the measurements. Table 1. Observed and simulated nitrogen balance. System N applied(g-N m-2) N harvested(g-N m-2) N leached(g-N m-2) Measured Simulated Measured Simulated Slurry 0.9 LU ha-1 6.8 12.2 12.5 3.3 3.4 Slurry 1.4 LU ha-1 11.7 13.3 13.8 3.7 4.0 FYM+slurry 0.9 LU ha-1 7.1 12.3 11.4 3.3 3.3 FYM+slurry 1.4 LU ha-1 11.6 12.9 12.0 3.6 4.

A model simulation analyses of nitrate leaching – does soil organic matter pool structure or catch crop growth parameters matter most?

Modelling of soil organic matter (SOM) turnover has often been developed in order to or to predict crop fertilser demand or to analyse environmental impact of different agriculture management practices. Mechanistic simulation models can be used to predict the mineralization of nitrogen (N) in added organic matter, e.g. from animal manure or incorporated crop residues, and the timing of N availability to the succeeding crops. In this way, mechanistic models may be used to avoid excessive fertilisation and hence to minimise nitrate leaching. The objective of this work was therefore to analyse the consequences of applying different SOM and crop modules (differing in pool structure or parameterisation) in the soil-plant-atmosphere model Daisy on the simulated crop production, soil nitrogen dynamics and nitrate leaching. We addressed the following questions: i) How much are Daisy simulations of crop production as well as nitrate leaching affected by applying different SOM module structures or parameterisation? ii) Are simulations of nitrogen dynamics and nitrate leaching more affected by different choice of crop modules than choice of SOM modules? We used an extensive 6-year field experiment for comparing simulated and measured data. The experiment comprised 3-y perennial ryegrass and grass-clover pastures under different management and subsequently cropped to spring cereals (including catch crop) with different manuring strategies for 3 years

Impact of organic pig production systems on CO

Organic rules for grazing and access to outdoor areas in pig production may be met in different ways, which express compromises between considerations for animal welfare, feed self-reliance and negative environmental impact such as greenhouse gas emissions and nitrate pollution. This article compares the environmental impact of the main organic pig systems in Denmark. Normally, sows are kept in huts on grassland and finishing pigs are raised in stables with access to an outdoor run. One alternative practice is also rearing the fattening pigs on grassland all year round. The third method investigated was a one-unit pen system mainly consisting of a deep litter area under a climate tent and with restricted access to a grazing area. Using life cycle assessment (LCA) methodology, the emissions of greenhouse gases of the free range system were estimated to be 3.3 kg CO2-equivalents kg−1 live weight pig, which was significantly higher than the indoor fattening system and the tent system, yielding 2.9 and 2.8 kg CO2-eq. kg−1 pig, respectively. This was 7–22% higher compared with Danish conventional pig production but, due to the integration of grass-clover in the organic crop rotations these had an estimated net soil carbon sequestration. When carbon sequestration was included in the LCA then the organic systems had lower greenhouse gas emissions compared with conventional pig production. Eutrophication in nitrate equivalents per kg pig was 21–65% higher in the organic pig systems and acidification was 35–45% higher per kg organic pig compared with the conventional system. We conclude that, even though the free range system theoretically has agro-ecological advantages over the indoor fattening system and the tent system due to a larger grass-clover area, this potential is difficult to implement in practice due to problems with leaching on sandy soil. Only if forage can contribute to a larger proportion of the pigfeed uptake may the free range system be economically and environmentally competitive. Improvement of nitrogen cycling and efficiency is the most important factor for reducing the overall environmental load from organic pig meat. Presently, a system with pig fattening in stables and concrete-covered outdoor runs seems to be the best solution from an environmental point of view