Matthias Stolze

Enhanced top soil carbon stocks under organic farming

It has been suggested that conversion to organic farming contributes to soil carbon sequestration, but until now a comprehensive quantitative assessment has been lacking. Therefore, datasets from 74 studies from pairwise comparisons of organic vs. nonorganic farming systems were subjected to metaanalysis to identify differences in soil organic carbon (SOC). We found significant differences and higher values for organically farmed soils of 0.18 ± 0.06% points (mean ± 95% confidence interval) for SOC concentrations, 3.50 ± 1.08 Mg C ha−1 for stocks, and 0.45 ± 0.21 Mg C ha−1 y−1 for sequestration rates compared with nonorganic management. Metaregression did not deliver clear results on drivers, but differences in external C inputs and crop rotations seemed important. Restricting the analysis to zero net input organic systems and retaining only the datasets with highest data quality (measured soil bulk densities and external C and N inputs), the mean difference in SOC stocks between the farming systems was still significant (1.98 ± 1.50 Mg C ha−1), whereas the difference in sequestration rates became insignificant (0.07 ± 0.08 Mg C ha−1 y−1). Analyzing zero net input systems for all data without this quality requirement revealed significant, positive differences in SOC concentrations and stocks (0.13 ± 0.09% points and 2.16 ± 1.65 Mg C ha−1, respectively) and insignificant differences for sequestration rates (0.27 ± 0.37 Mg C ha−1 y−1). The data mainly cover top soil and temperate zones, whereas only few data from tropical regions and subsoil horizons exist. Summarizing, this study shows that organic farming has the potential to accumulate soil carbon.

Environmental impacts of organic and conventional agricultural products – Are the differences captured by life cycle assessment?

Comprehensive assessment tools are needed that reliably describe environmental impacts of different agricultural systems in order to develop sustainable high yielding agricultural production systems with minimal impacts on the environment. Today, Life Cycle Assessment (LCA) is increasingly used to assess and compare the environmental sustainability of agricultural products from conventional and organic agriculture. However, LCA studies comparing agricultural products from conventional and organic farming systems report a wide variation in the resource efficiency of products from these systems. The studies show that impacts per area farmed land are usually less in organic systems, but related to the quantity produced impacts are often higher. We reviewed 34 comparative LCA studies of organic and conventional agricultural products to analyze whether this result is solely due to the usually lower yields in organic systems or also due to inaccurate modeling within LCA. Comparative LCAs on agricultural products from organic and conventional farming systems often do not adequately differentiate the specific characteristics of the respective farming system in the goal and scope definition and in the inventory analysis. Further, often only a limited number of impact categories are assessed within the impact assessment not allowing for a comprehensive environmental assessment. The most critical points we identified relate to the nitrogen (N) fluxes influencing acidification, eutrophication, and global warming potential, and biodiversity. Usually, N-emissions in LCA inventories of agricultural products are based on model calculations. Modeled N-emissions often do not correspond with the actual amount of N left in the system that may result in potential emissions. Reasons for this may be that N-models are not well adapted to the mode of action of organic fertilizers and that N-emission models often are built on assumptions from conventional agriculture leading to even greater deviances for organic systems between the amount of N calculated by emission models and the actual amount of N available for emissions. Improvements are needed regarding a more precise differentiation between farming systems and regarding the development of N emission models that better represent actual N-fluxes within different systems. We recommend adjusting N- and C-emissions during farmyard manure management and farmyard manure fertilization in plant production to the feed ration provided in the animal production of the respective farming system leading to different N- and C-compositions within the excrement. In the future, more representative background data on organic farming systems (e.g. N content of farmyard manure) should be generated and compiled so as to be available for use within LCA inventories. Finally, we recommend conducting consequential LCA - if possible - when using LCA for policy-making or strategic environmental planning to account for different functions of the analyzed farming systems.

Greenhouse gas fluxes from agricultural soils under organic and non-organic management — A global meta-analysis

It is anticipated that organic farming systems provide benefits concerning soil conservation and climate protection. A literature search on measured soil-derived greenhouse gas (GHG) (nitrous oxide and methane) fluxes under organic and non-organic management from farming system comparisons was conducted and followed by a meta-analysis. Up to date only 19 studies based on field measurements could be retrieved. Based on 12 studies that cover annual measurements, it appeared with a high significance that area-scaled nitrous oxide emissions from organically managed soils are 492 ± 160 kg CO2 eq. ha(-1) a(-1) lower than from non-organically managed soils. For arable soils the difference amounts to 497 ± 162 kg CO2 eq. ha(-1) a(-1). However, yield-scaled nitrous oxide emissions are higher by 41 ± 34 kg CO2 eq. t(-1) DM under organic management (arable and use). To equalize this mean difference in yield-scaled nitrous oxide emissions between both farming systems, the yield gap has to be less than 17%. Emissions from conventionally managed soils seemed to be influenced mainly by total N inputs, whereas for organically managed soils other variables such as soil characteristics seemed to be more important. This can be explained by the higher bioavailability of the synthetic N fertilisers in non-organic farming systems while the necessary mineralisation of the N sources under organic management leads to lower and retarded availability. Furthermore, a higher methane uptake of 3.2 ± 2.5 kg CO2 eq. ha(-1) a(-1) for arable soils under organic management can be observed. Only one comparative study on rice paddies has been published up to date. All 19 retrieved studies were conducted in the Northern hemisphere under temperate climate. Further GHG flux measurements in farming system comparisons are required to confirm the results and close the existing knowledge gaps.

Impacts of feeding less food-competing feedstuffs to livestock on global food system sustainability.

Increasing efficiency in livestock production and reducing the share of animal products in human consumption are two strategies to curb the adverse environmental impacts of the livestock sector. Here, we explore the room for sustainable livestock production by modelling the impacts and constraints of a third strategy in which livestock feed components that compete with direct human food crop production are reduced. Thus, in the outmost scenario, animals are fed only from grassland and by-products from food production. We show that this strategy could provide sufficient food (equal amounts of human-digestible energy and a similar protein/calorie ratio as in the reference scenario for 2050) and reduce environmental impacts compared with the reference scenario (in the most extreme case of zero human-edible concentrate feed: greenhouse gas emissions −18%; arable land occupation −26%, N-surplus −46%; P-surplus −40%; non-renewable energy use −36%, pesticide use intensity −22%, freshwater use −21%, soil erosion potential −12%). These results occur despite the fact that environmental efficiency of livestock production is reduced compared with the reference scenario, which is the consequence of the grassland-based feed for ruminants and the less optimal feeding rations based on by-products for non-ruminants. This apparent contradiction results from considerable reductions of animal products in human diets (protein intake per capita from livestock products reduced by 71%). We show that such a strategy focusing on feed components which do not compete with direct human food consumption offers a viable complement to strategies focusing on increased efficiency in production or reduced shares of animal products in consumption.

Strategies for feeding the world more sustainably with organic agriculture

Organic agriculture is proposed as a promising approach to achieving sustainable food systems, but its feasibility is also contested. We use a food systems model that addresses agronomic characteristics of organic agriculture to analyze the role that organic agriculture could play in sustainable food systems. Here we show that a 100% conversion to organic agriculture needs more land than conventional agriculture but reduces N-surplus and pesticide use. However, in combination with reductions of food wastage and food-competing feed from arable land, with correspondingly reduced production and consumption of animal products, land use under organic agriculture remains below the reference scenario. Other indicators such as greenhouse gas emissions also improve, but adequate nitrogen supply is challenging. Besides focusing on production, sustainable food systems need to address waste, crop–grass–livestock interdependencies and human consumption. None of the corresponding strategies needs full implementation and their combined partial implementation delivers a more sustainable food future.Organic agriculture requires fewer inputs but produces lower yields than conventional farming. Here, via a modeling approach, Muller et al. predict that if food waste and meat consumption are reduced, organic agriculture could feed the world without requiring cropland expansion.

Organic supply chain collaboration: a case study in eight EU countries

This study aims at contributing to a better understanding of the linkage between supply chain performance and possible performance improvement with respect to food quality and safety. Therefore, the article addresses the question whether the level of collaborative planning and close supply chain relationships could help improve the quality and safety of organic supply chains. The study was conducted as part of the multi-disciplinary EU-wide survey of organic supply chains, carried out in eight European countries. In this article we report the results of the study regarding the structures and performance of six different organic supply chains in these eight European countries for: milk (CH, UK), apples (DE, CH), pork (UK, NL), eggs (DE, UK), wheat (HU, IT, FR) and tomatoes (IT, NL). In-depth interviews with key-informants were carried out in 2006 to investigate the structures, performance, and relationships within the supply chains. Results show a low level of collaboration among various actors especially in cost and benefit sharing. Highly integrated supply chains show higher collaboration especially in the domain of Decision Synchronization. Trust and collaboration appear to be related with increased performance, whereas the higher the perceived risk for quality and safety, the higher the probability of supply chain collaboration.

How the organic food system supports sustainable diets and translates these into practice

Organic production and consumption provide a delineated food system that can be explored for its potential contribution to sustainable diets. While organic agriculture improves the sustainability performance on the production side, critical reflections are made on how organic consumption patterns, understood as the practice of people consuming significant amounts of organic produce, may also be taken as an example for sustainable food consumption. The consumption patterns of regular organic consumers seem to be close to the sustainable diet concept of FAO. Certain organic-related measures might therefore be useful in the sustainability assessment of diets, e.g., organic production and organic consumption. Since diets play a central role in shaping food systems and food systems shape diets, the role of organic consumption emerges as an essential topic to be addressed. This role may be based on four important organic achievements: organic agriculture and food production has a definition, well-established principles, public standards, and useful metrics. By 2015, data for organic production and consumption are recorded annually from more than 160 countries, and regulations are in force in more than 80 countries or regions. The organic food system puts the land (agri-cultura) back into the diet; it is the land from which the diet in toto is shaped. Therefore, the organic food system provides essential components of a sustainable diet.

Sustainability assessment of GM crops in a Swiss agricultural context

The aim of this study was to provide an ex ante assessment of the sustainability of genetically modified (GM) crops under the agricultural conditions prevailing in Switzerland. The study addressed the gaps in our knowledge relating to (1) the agronomic risks/benefits in production systems under Swiss conditions (at field and rotation/orchard level), (2) the economic and socio-economic impacts associated with altered farming systems, and (3) the agro-ecological risks/benefits of GM crops (at field and rotation/orchard level). The study was based on an inventory of GM crops and traits which may be available in the next decade, and on realistic scenarios of novel agricultural practices associated with the use of GM crops in conventional, integrated, and organic farming systems in Switzerland. The technology impact assessment was conducted using an adapted version of the matrix for “comparative assessment of risks and benefits for novel agricultural systems” developed for the UK. Parameter settings were based on information from literature sources and expert workshops. In a tiered approach, sustainability criteria were defined, an inventory of potentially available, suitable GM crops was drawn up, and scenarios of baseline and novel farming systems with GM crops were developed and subsequently submitted to economic, socio-economic, and agro-ecological assessments. The project had several system boundaries, which influenced the outcomes. It was limited to the main agricultural crops used for food and feed production and focused on traits that are relevant at the field level and are likely to be commercially available within a decade from the start of the project. The study assumed that there would be no statutory restrictions on growing GM crops in all farming systems and that they would be eligible for direct payments in the same way as non-GM crops. Costs for co-existence measures were explicitly excluded and it was assumed that GM foods could be marketed in the same way as non-GM foods at equal farm gate prices. The following model GM crops were selected for this study: (1) GM maize varieties with herbicide tolerance (HT), and with resistance to the European corn borer (Ostrinia nubilalis) and the corn rootworm (Diabrotica virgifera); (2) HT wheat; (3) GM potato varieties with resistance to late blight (Phytophthora infestans), to the nematode Globodera spp., and to the Colorado beetle (Leptinotarsa decemlineata); (4) HT sugar beet with resistance to “rhizomania” (beet necrotic yellow vein virus; BNYVV); (5) apples with traditionally bred or GM resistance to scab (Venturia inaequalis), and GM apples with stacked resistance to scab and fire blight (Erwinia amylovora). Scenarios for arable rotations and apple orchards were developed on the basis of the model crops selected. The impact assessments were conducted for the entire model rotations/orchards in order to explore cumulative effects as well as effects that depend on the farming systems (organic, integrated, and conventional). In arable cropping systems, herbicide tolerance had the most significant impact on agronomic practices in integrated and conventional farming systems. HT crops enable altered soil and weed management strategies. While no-till soil management benefited soil conservation, the highly efficient weed control reduced biodiversity. These effects accumulated over time due to the high proportion of HT crops in the integrated and conventional model rotations. In organic production systems, the effects were less pronounced, mainly due to non-use of herbicides. Traits affecting resistance to pests and diseases had a minor impact on the overall performance of the systems, mainly due to the availability of alternative crop protection tools or traditionally bred varieties. The use of GM crops had only a minor effect on the overall profitability of the arable crop rotations. In apple production systems, scab and fire blight resistance had a positive impact on natural resources as well as on local ecology due to the reduced need for spray passages and pesticide use. In integrated apple production, disease resistance increased profitability slightly, whereas in the organic scenario, both scab and fire blight resistance increased the profitability of the systems substantially. In conclusion, the ecological and socio-economic impacts identified in this study were highly context sensitive and were associated mainly with altered production systems rather than with the GM crops per se.

Environmental performance of organic farming

As a typical cradle-to-cradle approach, organic farming suits the notion of a green technology. However, a generally valid quantification of the environmental performance of organic agriculture is difficult because there is a high variability between countries, regions, farm types, and products. Furthermore, different assessment methods lead to partly contradicting conclusions on the environmental impacts of organic farming. This chapter gives an overview on the environmental impacts of organic agriculture compared with those of conventional agriculture based on state-of-the-art literature and discusses methodological implications for the comparison of environmental impacts of farming systems. According to most of the reviewed literature organic farming performs better in terms of biodiversity, soil fertility and air quality, mitigating resource depletion, climate change mitigation, and groundwater pollution as compared with conventional agriculture. However, there are single environmental indicators in some of the above-mentioned fields, against which organic agriculture performs equally or even worse (N2O emissions and CH4 emissions per unit of product produced), depending on the assumptions and methodology of the study. Finally, this paper highlights nine common methodological problems of quantifying environmental impacts of farming systems that have been identified in the reviewed literature and suggests solutions for improvement.

The challenges of including impacts on biodiversity in agricultural life cycle assessments

Agriculture is considered to be one of the main drivers for worldwide biodiversity loss but the impacts of agricultural production on biodiversity have not been extensively considered in Life Cycle Assessments (LCAs). Recent realisation that biodiversity impact should be included in comprehensive LCAs has led to attempts to develop and implement methods for biodiversity impact assessment. In this review, twenty-two different biodiversity impact assessment methods have been analysed to identify their strengths and weaknesses in terms of their comprehensiveness in the evaluation of agricultural products. Different criteria, which had to meet the specific requirements of biodiversity research, life cycle assessment methodology, and the evaluation of agricultural products, were selected to investigate the identified methods. Very few of the methods were developed with the specific intention of being used for agricultural LCAs. Furthermore, none of the methods can be applied globally while at the same time being able to differentiate between various agricultural intensities. Global value chains and the increasing awareness of different biodiversity impacts of agricultural production systems demand the development of evaluation methods that are able to overcome these shortcomings. Despite the progress that has already been achieved, there are still unresolved difficulties which need further research and improvement.