Vergleich der Klimarelevanz ökologischer und konventioneller Landbewirtschaftung

Die Charakterisierung der mit den Begriffen "Ökologischer" und "Konventioneller" Landbau bezeichneten Wirtschaftsweise bleibt ebenso wie der Vergleich dieser landwirtschaftlichen Produktionssysteme auf den für die Studie notwendigen Rahmen begrenzt. Emissions- und Senken- Potentiale von klimarelevanten Gasen im Agrarsektor werden im Systemvergleich erarbeitet. Die aktuellen Ergebnisse der beteiligten Studiennehmer innerhalb des Studienprogramms "Landwirtschaft" der Enquetekommission zu den landwirtschaftlichen Emissionen von klimarelevanten Gasen konnten leider nicht in diese Studie eingearbeitet werden, da sie zeitgleich erstellt wurden. Zwar ist der Anteil des Agrarsektors am nationalen Gesamtenergieverbrauch in den Industrieländern nur gering, aber der Energieeinsatz ist für den Primärsektor Landwirtschaft von grundsätzlicher Bedeutung und bildet auch vor dem Hintergrund der aktuellen agrarpolitischen Diskussion zu nachwachsenden Energieträgern einen weiteren Schwerpunkt dieser Studie. Die Nutzungspotentiale regenerativer Energieressourcen sind in den beiden betrachteten Produktionssystemen in unterschiedlichem Maße realisierbar. Die Restriktionen im Ökologischen Landbau ebenso wie die daraus ableitbaren Konsequenzen für die künftige Ausrichtung der Flächennutzung werden dargelegt. Die systembedingt unterschiedlichen Anpassungspotentiale an den prognostizierten Klimawandel können mangels regionaler Auflösung der Vorhersagen und ungenügendem Grundlagenwissen nur angedeutet werden. Von grundsätzlicher Bedeutung ist die "Streßsituation" von Agrarökosystemen bei sich ändernden Umwelt- und Klimaverhältnissen. Die Darstellung unterschiedlicher Wirkungen von Anbausystemen des Konventionellen und des Ökologischen Landbaus wird schwerpunktmäßig für die BR Deutschland bzw. Nordwesteuropa vorgenommen. Ergebnisse eines Vergleichs dieser Agrarsysteme in Entwicklungsländern (Agroforstsysteme, Monokulturen von Export-cash-crops) können im Rahmen dieser Studie nur angedeutet werden. Konsumenten ökologisch produzierter Lebensmittel zeigen in ihrem Kaufverhalten differenzierte Verbrauchspräferenzen. Ein verändertes Nachfrageverhalten hat für den Vergleich verschiedener Anbausysteme eine entscheidende Bedeutung. Ebenso sind bei der gesamthaften vergleichenden Betrachtung von unterschiedlichen landwirtschaftlichen Produktionssystemen u.a. der Energieaufwand für verschiedene Vermarktungswege (Ferntransport, Erfassungsaufwand, Produktionsstättendichte etc.) und Verarbeitungs¬formen mit einzubeziehen. Diese Schnittstelle zwischen landwirtschaftlicher Erzeugung und dem Konsum von Lebensmitteln ist Inhalt der Folgestudie "Landwirtschaft und Ernährung" innerhalb des Studienprogramms "Landwirtschaft" der Enquete-Kommission "Schutz der Erdatmosphäre". Schwerpunkt der vorliegenden Studie bildet deshalb die landwirtschaftliche Produktion selbst

Nutrient cycle on organic farms: stall balance of a suckler herd and beef bulls

In organic agriculture, the internal farm nutrient cycle must be quantified to ensure high system productivity along with environmentally sound production processes. In contrast to common farmgate and field balances, budgeting at the stable level is seldom undertaken. When budgeting mixed farming systems, a substantial lack of nutrients can be detected in the nutrient flow chain "forage and straw input - stable - manure output". Therefore, stable balances focus on a central component of whole farm nutrient budgets for developing efficient nutrient management strategies. At the experimental farm for organic agriculture Wiesengut in Hennef, Germany, all solid mass flows for a suckler herd and a herd of beef bulls were measured. Relative balance values obtained for dry matter and C (45 to 56%), N (16 to 36%), P (-7 to 22.5%), K (0 to 13%) and ash (-4 to 7%) showed a wide range. Balances are very sensitive to variations in mass flow and nutrient content for components with high nutrient contents and/or a large contribution to total mass flow (e.g. manure, silage). In developing strategies to minimize N losses, by reducing N surplus in the ration, it has to be considered, that in contrast to dairy farms, a suckler herd for beef production integrated in an organic farm has to adapt to crop production demands. from: HAAS, G., B. CASPARI, U. KÖPKE 2002: Nutrient cycle on organic farms: stall balance of a suckler herd and beef bulls. Nutrient Cycling in Agroecosystems 64, 225-230

Farm gate nutrient balances of organic dairy farms at different intensity levels in Germany

Organic farms are characterized as low external input agro-ecosystems. Currently, some organic dairy farmers feed higher amounts of concentrates and succulent feed, some of which is purchased, to increase the dairy performance of their cows. To assess the environ¬mental impact of this practice, nutrient balances at the farm-gate level of 26 organic dairy farms located in two different regions in Germany were compiled and analysed. The farms are characterised by different production features and feeding intensity levels (0 - 2.72 t DM of concentrates per cow and year, which was 0 - 378 g kg-1 milk) yielding 5,150 - 8,790 kg milk on average per cow and year. The area- and product- (milk) related farm-gate nutrient budgets for P and K are almost balanced (mean -3 kg P ha-1, range (R): -14 to 4 kg P ha-1; -0.5 g P kg-1 milk, R: -2.8 to 0.9 g P kg-1 milk and 1 kg K ha-1, R: -13 to 15 kg K ha-1; 0.1 g K kg-1 milk, R: -2.4 to 3.9 g K kg-1 milk). The N surplus averages only 43 kg ha-1 (R: 8 to 85 kg N ha-1) and 8.2 g kg-1 milk (R: 2.1 to 17.1 g kg-1 milk), but the correlation between the amount of feed purchased on a net basis and N surplus is significant (r = 0.56, p = 0.003). Average area-related nutrient use efficiency for all farms calculated as the proportion of input to output is high for N (45%), P (164%) and K (91%). The share of nutrient input and output components and correlations between parameters are presented. To classify the results, investigations comparing organic and conventional dairy farming in Europe are listed, indicating an N surplus for organic farms, which is often only half or a third of the surplus of conventional farms. However, intensification in organic dairy farming has, in some cases, significant impacts that need to be assessed to determine its environmental performance and profile

Estimation of environmental impact of conversion to organic agriculture in Hamburg using the Life-Cycle-Assessment method

Commissioned by the Ministry of Environment of Hamburg, Germany, an environmental impact assessment using the Life-Cycle Assessment (LCA) method was carried out during 1995 and 1996. In a scenario, the effect of a complete transition from conventional to organic agriculture of about 5,674 ha and 4,669 livestock units in a rural part of Hamburg was investigated using 9 impact categories. The study was based on the analysis of 15 farms representative of the farms in the region, mainly dairy and beef cattle farms with some cash crops, in close cooperation with local advisers and other experts. Several workshops were held to integrate the local public, in particular the experts and administrative staff related to farming and nature protection. It was estimated for the study area for the year 1995 that through the conversion to organic agriculture, the eutrophication potential could be lowered by reducing the nitrogen (N) surplus by 75% (from 311 t to 77 t) and turning the phosphate (P) surplus of 47 t into a deficit of 19 t. The ammonia emission decreased to 69% of the conventional level (from 238 t to 165 t) resulting in a similar reduction of the acidification potential (from 474 t to 328 t SO2-equivalents). Compared to conventional farming, 55% of the primary energy was saved by organic agriculture (38,540 instead of 84,760 GJ), which also lowered the global warming potential by 31% from 26,365 t to 18,271 t CO2-equivalents. No pesticides were used, thus saving about 22.7 t of chemical agents. This would lead to positive effects in the impact categories drinking water quality, human toxicity and ecotoxicity, especially as most pesti¬cides were applied illegally and not in compliance with the regulations regarding minimum distance to surface water. The biodiversity impact assessed by evaluating several indicators during field visits showed a clear improvement for arable land, permanent grassland and landscape structures (such as ditches and field boundaries). No differences were determined for the categories soil protection and landscape image due to specific site conditions and cropping system effects. The study confirmed the suitability of the LCA approach for com¬paring different farming systems. However, the results led to strong reactions from some experts and particularly farmers and their representatives

Potential income gains for rural households in North Eastern Thailand through trade with organic products

The study groups households in North Eastern Thailand according their income and grade of specialisation in crop production to derive representative household types. For these household types a linear optimization model is run to calculate net incomes under four scenarios. These are certified organic farming, organic farming in the initial and transitional phase and a self-sufficient farming. Simulations for the different management scenarios show that per ha cash profits are about double under certification while they can only be increased by 30 percent under self-sufficient farming, even under favourable assumptions. But transition costs to organic farming are high due to reduced yields at the beginning. According to the figures and model used, only under certified organic production it pays to hire non household workers. Labour hence is a major limiting factor.organic agriculture, Thailand, household income, Consumer/Household Economics, International Relations/Trade,

Nitrate leaching: comparing conventional, integrated and organic agricultural production systems

The impact of conventional, integrated and organic practices on groundwater quality were studied in northwestern Germany. Between 1993 and 1997 nitrogen budgets and the nitrate content of the unsaturated zone (soil sampling and porous suction cups) were measured in two field trials located on a clayey loam and a loamy sand, respectively. In each year of investigation three main crops per farming system were compared according to the defined site(soil)-adapted crop rotation. There was little decrease in the NO3-concentration of the percolate and the amount of leached N (15% less) by shifting from conventional practice to integrated farming. Converting to organic farming reduced leaching losses of nitrogen by more than 50 %. Yields of the organic field plots were lower, but comparing the cash crop yields in relation to the amount of leached nitrate, the production efficiency (nitrate-N leached related to yield of crops) of the organic farming system was still clearly higher. from: HAAS, G., M. BERG & U. KÖPKE 2002: Nitrate leaching: comparing conventional, integrated and organic agricultural production systems. In: Agricultural Effects on Ground and Surface Waters - Research at the Edge of Science and Society. S. 131-136. International Association of Hydrological Science 273

Comparing intensive, extensified and organic grassland farming in southern Germany by process life cycle assessment

To reduce the environmental burden of agriculture, suitable methods to comprehend and assess the impact on natural resources are needed. One of the methods considered is the life cycle assessment (LCA) method, which was used to assess the environmental impacts of 18 grassland farms in three different farming intensities - intensive, extensified, and organic - in the Allgäu region in southern Germany. Extensified and organic compared with intensive farms could reduce negative effects in the abiotic impact categories of energy use, global warming potential and ground water mainly by renouncing mineral nitrogen fertilizer. Energy consumption of intensive farms was 19.1 GJ/ha and 2.7 GJ/t milk, of extensified and organic farms 8.7 and 5.9 GJ/ha along with 1.3 and 1.2 GJ/t milk, respectively. Global warming potential was 9.4, 7.0 and 6.3 t CO2-equivalents/ha and 1.3, 1.0 and 1.3 t CO2-equivalents/t milk for the intensive, extensified and organic farms, respectively. Acidification calculated in SO2-equivalents was high, but the extensified (119 kg SO2/ha) and the organic farms (107 kg SO2/ha) emit a lower amount compared with the intensive farms (136 kg SO2/ha). Eutrophication potential computed in PO4-equivalents was higher for intensive (54.2 kg PO4/ha) compared with extensified (31.2 kg PO4/ha) and organic farms (13.5 kg PO4/ha). Farmgate balances for N (80.1, 31.4 and 31.1 kg/ha) and P (5.3, 4.5 and -2.3 kg/ha) for intensive, extensified and organic farms, respectively, indicate the different impacts on ground and surface water quality. Analysing the impact categories biodiversity, landscape image and animal husbandry, organic farms had clear advantages in the indicators number of grassland species, grazing cattle, layout of farmstead and herd management, but indices in these categories showed a wide range and are partly independent of the farming system. from: HAAS, G., F. WETTERICH, U. KÖPKE 2001: Comparing intensive, extensified and organic grassland farming in southern Germany by process life cycle assessment. Agriculture, Ecosystems & Environment 83/1-2, 43-53

Reexamining Blackbody Shifts for Hydrogenlike Ions

We investigate blackbody-induced energy shifts for low-lying levels of atomic systems, with a special emphasis on transitions used in current and planned high-precision experiments on atomic hydrogen and ionized helium. Fine-structure- and Lamb-shift-induced blackbody shifts are found to increase with the square of the nuclear charge number, whereas blackbody shifts due to virtual transitions decrease with increasing nuclear charge as the fourth power of the nuclear charge. We also investigate the decay width acquired by the ground state of atomic hydrogen, due to interaction with blackbody photons. The corresponding width is due to an instability against excitation to higher excited atomic levels, and due to blackbody-induced ionization. These effects limit the lifetime of even the most fundamental, a priori absolutely stable, asymptotic state of atomic theory, namely, the ground state of atomic hydrogen