Browsing by Subject "Biologische Landwirtschaft"

Now showing 1 - 5 of 5
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    Economic analysis of organic certification systems : determinants of non-compliance and optimum control strategies
    (2012) Zorn, Alexander; Dabbert, Stephan
    Organic certification systems are prerequisite for the existence of a large-scale organic food market. Despite a well-established and generally effective control system, fraud regarding organic food that passed organic controls is detected regularly. This cumulative thesis consisting of four articles addresses current questions regarding the improvement of organic certification systems. The need for governmental supervision of an organic certification system run by private control bodies is demonstrated by a game theoretic model. A framework prepares the statistical analysis by conceptually linking factors that can influence organic control results. The case study on German supervision data from the years 2006 to 2008 reveals significant differences between private control bodies regarding the number of severe sanctions imposed, i.e. fundamental control results. These data that were collected for supervision of the control system, however, are not sufficient to explain these differences. This is due to shortcomings in the data collected. Key terms of the data are not defined and the variable definitions seem to change over time. This study concludes that there is more detailed and reliable data from organic control bodies needed to understand the determinants of non-compliance with an organic standard. Detailed data on organic farm controls from the years 2007 to 2009 were supplied by two control bodies. Theoretical considerations founded on the ?Economics of Crime? approach yield hypotheses on factors affecting non-compliance with an organic standard. The data provided by a German and a Swiss control body are analysed by two different logistic regression models. The probability of receiving a sanction (which is used as proxy for non-compliance) is estimated on farm level by using data on farm and farm production. Such an approach to assess the determinants of non-compliance has not been used previously in the literature. Given the gradual sanction system, an ordinal logistic regression model is appropriate for the analysis of the German data. Swiss data are analysed by a random effects logistic regression model. Both models confirm some of the factors contributing to the risk of non-compliance that are applied in qualitative risk assessment so far. Control results from previous years, the overall farm complexity and the farm livestock production complexity, as well as farm size are factors that increase the probability of receiving a sanction. Risks connected to specific crops or livestock types that could come along, e.g., with particular requirements of the production method cannot be confirmed across the models. The explanatory value of both models is likely to be improved by the integration of further variables, such as data on farmers? personal and financial characteristics. The heuristic model builds on the results of the econometric models. This model adopts a societal view on the control system by considering the costs of controls and the damages resulting from non-compliance with an organic standard. Monte-Carlo simulations illustrate the relationship between important parameters for optimising control strategies. These simulations show that even without fines a situation can occur where most operators comply. The different approaches to analyse control data encounter difficulties inherent to the control data. In this context, the dark figure consisting of undetected non-compliances, inhomogeneous detection probabilities linked to particular production methods, and a potential positive confirmation bias connected to the risk based control approach are especially relevant. The working hypothesis that these potential biases are distributed randomly deserves closer attention in subsequent studies. Such future analysis should be based on even more detailed data, e.g., pooling original data from different control bodies in a control system. Such a data base would allow focusing on severe non-compliances which occur only rarely. Furthermore, pooled data could be used to investigate issues that are fundamental for the supervision of a control system such as a control body effect on the detection of non-compliance. This thesis presents important results that can be consulted for further analysis of organic control systems. Beyond, the approach, the methods used, and the results obtained are of general relevance for food certification systems beyond the organic sector.
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    Feldstudie zur Eignung der Biophotonenmessung für die Differenzierung von ökologisch und konventionell erzeugten Hühnereiern
    (2009) Egerer, Ulrike; Grashorn, Michael
    Consumer demand for organic food is increasing. Conventional quality criteria are based on assay of individual chemical compounds, which depend much more on local conditions, climate and breed than on the production method. So alternatives need to be found to distinguish between organic and conventional food. Complementary approaches look at biological systems as a whole and focus on the inner structure of products. As shown in many studies, holistic criterions reflect differences in food quality, which are caused by the production method. F.A. POPP has rediscovered ultra weak light emissions that are presumed to originate from electromagnetic fields in living organisms. So-called 'biophotons' can be detected by highly sensitive photomultipliers as 'delayed luminescence' after illumination of the sample. Associated with living processes, the radiation reflects the state of the living tissue. In 2001 B. KÖHLER showed that egg yolks emit varying biophoton intensities depending on the husbandry system. Using standardized test conditions KÖHLER found that exposition to sunlight or to lighting that was similar to daylight, as well as feeding of green stuff, enhanced biophoton emission of yolks. The present investigation has been carried out under conditions of commercial egg production to discover whether biophoton emission is a suitable quality criterion for organic eggs. From July 2005 to November 2006, about 900 eggs have been collected in food stores and on farms. The biophoton intensity of each egg was determined and entered into a database according to its way of production (cage, deep litter, free-range, organic or from smallholders). The aim of this examination was to determine the differences in light emission of eggs originating from various production systems without standardized husbandry conditions. As a second project, a long-term observation has been conducted to see whether biophoton values of eggs remain stable over time. During the course of one year (from May 2006), biophoton emission has been measured each month. Samples have been taken from twelve hen houses with different husbandry systems: 2 houses with cage system, 4 with deep litter, 2 houses with free-range system and 4 organic farms ? adding up to more than 2,300 eggs. In addition to the measurement of biophoton emissions, conventional egg quality criteria have also been determined: egg mass, breaking strength of egg shell, albumen height, yolk color, proportion of yolk, fatty acid profile and lipid oxidation. Farmers have been interviewed about the age of their hens, flock size, lighting conditions and feed composition. Climatic conditions have been researched on the internet. It was expected that comparison of all collected data would give information on the origin and meaning of biophoton emission of egg yolks. In the present studies yolks were exposed to white light for 30 seconds. Delayed luminescence was detected for the duration of 60 seconds. The biophoton parameter used has been defined as the sum of light emission during the last 40 seconds of the measurement. Egg yolks from different animal husbandry systems differed in biophoton emissions. However, while conventionally produced egg yolks showed only minor differences, organic eggs as well as eggs from smallholders were characterized by clearly higher intensities. The long-term observation of yolks from 12 selected hen houses revealed great fluctuation of biophoton emissions over the course of the year. Nevertheless, it was remarkable that yolk samples with low contents of saturated fatty acids and high contents of polyunsaturated fatty acids showed the highest biophoton intensities. These samples originated from farms that offer both a green free range and feed including vegetables or dried grass. As KÖHLER had shown, feeding green stuff leads to higher light emissions of yolks and also influences the profile of fatty acids. Further examinations will be necessary to clarify the causality between fatty acid composition of the yolk and its biophoton emission. Another target of the described projects was to test the suitability of biophoton measurement for verifying the organic origin of eggs. In discriminant analyses egg samples of both studies were assigned to the categories 'organic' or 'conventional' according to their emission values. The hit ratio was about 70 %. This result is interesting considering the lack of techniques to distinguish between organically and conventionally produced eggs up to now. Optimization of measuring technique and procedure may improve the capability of the method. In any case, biophoton measurement could be used as a screening method. Detection of extremely low values would suggest a check of management conditions at the relevant farm, followed by comparison with standards for the respective animal husbandry system.
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    Nitrogen dynamics in organic and conventional farming systems in the sub-humid highlands of central Kenya
    (2019) Musyoka, Martha; Cadisch, Georg
    Nitrogen (N) deficit is one of the limiting factors to food security in most developing countries while the excessive use of N has resulted in environmental contamination. Timely N availability, at the right rate is crucial to improving crop yield and N use efficiency in farming systems. Therefore, understanding nitrogen dynamics under different farming systems is essential to improve N use and recovery efficiencies of crops and in addressing environmental impacts associated with increased use of inorganic and organic inputs. This study focused on N dynamics in conventional (Conv) and organic (Org) farming systems as practiced by small scale farmers (at ∼50 kg N ha−1yr−1, Low input) and at recommended levels of input (∼225 kg N ha−1yr−1, High input) for commercial use in the sub humid and humid regions of Central Kenya. Data was collected during three cropping seasons between October 2012 and March 2014 in an on-going long-term trial established since 2007 at Chuka and at Thika sites located in central highlands of Kenya. Mineral N-based fertilizer and cattle manure were applied in Conv-High and Conv-Low while composts and other organic inputs were applied at similar N rates for Org-High and Org-Low. Farming systems were laid down in a randomized complete block design with 4 and 5 replications at Chuka and Thika respectively. The trial follows a 2 season-three-year crop rotation envisaging maize, legumes, vegetables and potatoes. N mineralization was studied using a modified buried bag approach while N loss was measured using Self-Integrating Accumulator (SIA) cores. N synchrony was assessed using daily N flux differences constructed as daily N release minus daily N uptake at different stages of the crops. N uptake was assessed at various stages of the crop through destructive sampling while nitrogen use efficiency (NUE) was assessed at harvest. Surface N balances were constructed using N applied as inputs, N deposition via rainfall, biological N fixation and crop yield and biomass as outputs. Out of the total N applied from inputs, only 61, 43 and 71 % was released during potato, maize and vegetable seasons respectively. Farming systems did not show a major impact in their influence on N synchrony, i.e. matching N supply to meet N demand. Rather the N synchrony varied with crop and N demand stages. Positive N flux differences were observed (higher N release compared to N demand) during the initial 20-30 days of incubation for all the farming systems, and negative N flux differences (higher N demand than release) at reproductive stages of the crops. Nitrogen uptake efficiency (NUpE) of potato was highest in Conv-Low and Org-Low at Thika and lowest in Org-High and Org-Low at Chuka where late blight disease affected potato performance. In contrast, NUpE of maize was similar in all systems at Chuka site, but was significantly higher in Conv-High and Org-High compared to the low input systems at Thika site. The NUpE of cabbage was similar in Conv-High and Org-High while the NUpE of kale and Swiss chard were similar in the low input systems. Potato N utilization efficiencies (NUtE) and agronomic efficiencies of N use (AEN) in Conv-Low and Conv-High were higher than those from Org-Low and Org-High, respectively. The AEN of maize was similar in all the systems at Chuka but was higher in the high input systems compared to the low input systems at the site in Thika. The AEN of vegetables under conventional systems were similar to those from organic systems. Both conventional and organic systems lost substantial amounts of mineral-N into lower soil horizons before crop establishment (0-26 days). Cumulative NO3--N leached below 1 m was similar in all the farming systems but was higher at the more humid Chuka site compared to Thika site during the maize season. Significantly more N was leached during potato season compared to maize and vegetable seasons. When NO3--N leached was expressed over total N applied, 63-68% more NO3--N was leached from the low input systems compared to the high input systems. Org-High showed a positive partial N balance at both sites and in all the cropping systems except during the vegetable season at Chuka. All the other systems exhibited negative partial N balances for the three cropping seasons with exception of Conv-High during potato season and Conv-Low and Org-Low during vegetable season at Thika site. In summary, organic and conventional had similar effects on N release, synchrony and N loss through leaching. Furthermore, more N was leached (when expressed as a fraction of N applied) during potato and vegetables cropping seasons in the low input systems compared to the high input systems. In addition, conventional and organic farming systems had similar effects on NUpE, AEN, NUtE and NHI for maize and vegetables, while conventional systems improved NUE of potato compared to organic systems. The research therefore concludes that organic and conventional farming systems at high input level are viable options of increasing food security in sub-Saharan Africa (SSA) for maize and vegetables as demonstrated by similar yields, NUE, N supply and loss. Ability to meet food security in conventional and organic system at low input is hampered by high N losses, negative N balances coupled with low productivity due to biotic and abiotic stresses. In both conventional and organic systems, there is a need to reduce N application at planting and increase N applied at reproductive stages to minimize potential loss during the initial 20-30 days after application and improve N supply midseason when crop demand is high. Since organic systems depend on organic inputs, there is a critical need to improve the quality of manure, composts and other organic inputs to improve N supply and availability.
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    Towards a sustainable nutrient management in organic farming : closing the nutrient gap with recycled fertilizers from urban waste
    (2022) Reimer, Marie; Möller, Kurt
    Nutrient scarcity is one of the main challenges in arable organic farming. Yet, little is known about the current supply and need of nutrients on organic farms and even less about the nutrient sources utilized by organic farmers. However, most stakeholders within the organic sector agree that additional nutrients, preferably from recycled sources, such as urban waste materials, are needed. In this thesis, the current need and use of nutrients (N, P, K, Mg, S) in the organic farming systems was investigated by performing a meta-analysis of previous studies and two farm gate nutrient budget studies across Europe. Further, the effect of recycled fertilizers from urban waste, such as compost from household and green waste, human urine and sewage sludge on crop yield, nutrient balances, soil fertility, and risk of contamination with potentially toxic elements (PTEs) were examined. To this end, three long-term field trials using different recycled fertilizers were investigated and combined with results of a simulation using the soil-plant-atmosphere model DAISY. The results of this thesis show that the organic cropping system within Europe operates under nutrient limited conditions, which limits the yield potential and can cause soil nutrient depletion, especially of P. Farms that relied to a high extend (>60%) on biological nitrogen fixation for their N supply were particularly prone to the risk of soil P and K depletion. Further, 17% of external N inputs derived from the conventional livestock system, which is often considered contentious. Omitting these would further increase the nutrient gap. Therefore, changes to the contemporary practice are needed to ensure sustainability in the organic nutrient management. First, a better distribution of nutrients within the organic sector is needed. In particular, to avoid nutrient surpluses in one farm type (e.g., livestock or vegetable farms), while other farm types (e.g., arable farms) experience nutrient deficits. Further, due to N losses during processing the nutrient composition of organic fertilizers does not match the crops’ nutrient offtake. Digestates from biogas plant show the closest resemblance. However, to avoid nutrient imbalances an adequate use of external inputs that is tailored to the specific farm’s nutrient demands and reliance on biological N fixation is necessary. Increased awareness of tools like nutrient budgeting among farmers and advisors could facilitate achieving a more balanced nutrient management. Still, additional nutrients are needed to close the current nutrient gap and to substitute animal manures from conventional origin. Recycled fertilizers from urban waste represent a suitable nutrient source to this end. Sewage sludge and human urine performed similarly to cattle slurry with N recovery rates of about 0.5 – 0.6 and household waste compost had similar values to straw-rich animal manures with recovery rate of about 0.3. Nitrogen losses after field application ranged between 34-55% of the applied N amount, with nitrate leaching being the main loss pathway. Total N losses were slightly smaller for compost and cattle manure and were accompanied by a higher soil N accumulation of about 25% of applied N. Similar to the accumulation of soil N, compost also resulted in the highest soil C sequestration. Using cattle manures and sewage sludge showed a smaller effect, while cattle slurry did not cause a soil C increase. Most concerns related to the use of recycled fertilizers derive from the risk of contaminants, such as potentially toxic elements (PTEs). Compost and sewage sludge fertilization can lead to a higher amount of PTEs in the soil. However, significant changes in crop PTE uptake were rare due to low PTE bioavailability. The risk to human health and soil environment associated with PTEs through recycled fertilizer application is therefore neglectable. Urban waste can also be refined by incineration or precipitation processes to ensure less contamination, yet this results in nutrient (e.g., N) and organic matter loss. An argument can therefore be made for the use of raw materials if they lie within the contamination threshold values. In conclusion, the organic nutrient management in Europe requires more external nutrient inputs. Recycled fertilizers from urban wastes are an adequate source in terms of yield effect and soil fertility to close the nutrient gap and to substitute animal manures from conventional origin. However, the infrastructure and availability of recycled fertilizers need to be improved and suitable policy making is needed to fulfil the whole potential of these nutrient sources by for example permitting fertilizers derived from human excreta or the strategical placement of biogas plants which recycle urban wastes.