Low-input agricultural systems aim at reducing the use of synthetic fertilizers and pesticides in order to improve sustainable production and ecosystem health. Despite the integral role of the soil microbiome in agricultural production, we still have a limited understanding of the complex response of microbial diversity to organic and conventional farming. Here we report on the structural response of the soil microbiome to more than two decades of different agricultural management in a long-term field experiment using a high-throughput pyrosequencing approach of bacterial and fungal ribosomal markers. Organic farming increased richness, decreased evenness, reduced dispersion and shifted the structure of the soil microbiota when compared with conventionally managed soils under exclusively mineral fertilization. This effect was largely attributed to the use and quality of organic fertilizers, as differences became smaller when conventionally managed soils under an integrated fertilization scheme were examined. The impact of the plant protection regime, characterized by moderate and targeted application of pesticides, was of subordinate importance. Systems not receiving manure harboured a dispersed and functionally versatile community characterized by presumably oligotrophic organisms adapted to nutrient-limited environments. Systems receiving organic fertilizer were characterized by specific microbial guilds known to be involved in degradation of complex organic compounds such as manure and compost. The throughput and resolution of the sequencing approach permitted to detect specific structural shifts at the level of individual microbial taxa that harbours a novel potential for managing the soil environment by means of promoting beneficial and suppressing detrimental organisms.

/pdf/distinct-soil-microbial-diversity-under-long-term-organic-144uqbgvrm.pdf

Distinct soil microbial diversity under long-term organic and conventional farming

Soil organic matter and biological soil quality indicators after 21 years of organic and conventional farming

Organic farming may contribute substantially to future agricultural production worldwide by improving soil quality and pest control, thereby reducing environmental impacts of conventional farming. We investigated in a comprehensive way soil chemical, as well as below and aboveground biological parameters of two organic and two conventional wheat farming systems that primarily differed in fertilization and weed management strategies. Contrast analyses identified management related differences between “herbicide-free” bioorganic (BIOORG) and biodynamic (BIODYN) systems and conventional systems with (CONFYM) or without manure (CONMIN) and herbicide application within a long-term agricultural experiment (DOK trial, Switzerland). Soil carbon content was significantly higher in systems receiving farmyard manure and concomitantly microbial biomass (fungi and bacteria) was increased. Microbial activity parameters, such as microbial basal respiration and nitrogen mineralization, showed an opposite pattern, suggesting that soil carbon in the conventional system (CONFYM) was more easily accessible to microorganisms than in organic systems. Bacterivorous nematodes and earthworms were most abundant in systems that received farmyard manure, which is in line with the responses of their potential food sources (microbes and organic matter). Mineral fertilizer application detrimentally affected enchytraeids and Diptera larvae, whereas aphids benefited. Spider abundance was favoured by organic management, most likely a response to increased prey availability from the belowground subsystem or increased weed coverage. In contrast to most soil-based, bottom-up controlled interactions, the twofold higher abundance of this generalist predator group in organic systems likely contributed to the significantly lower abundance of aboveground herbivore pests (aphids) in these systems. Long-term organic farming and the application of farmyard manure promoted soil quality, microbial biomass and fostered natural enemies and ecosystem engineers, suggesting enhanced nutrient cycling and pest control. Mineral fertilizers and herbicide application, in contrast, affected the potential for top-down control of aboveground pests negatively and reduced the organic carbon levels. Our study indicates that the use of synthetic fertilizers and herbicide application changes interactions within and between below and aboveground components, ultimately promoting negative environmental impacts of agriculture by reducing internal biological cycles and pest control. On the contrary, organic farming fosters microbial and faunal decomposers and this propagates into the aboveground system via generalist predators thereby increasing conservation biological control. However, grain and straw yields were 23% higher in systems receiving mineral fertilizers and herbicides reflecting the trade-off between productivity and environmental responsibility.

/pdf/long-term-organic-farming-fosters-below-and-aboveground-4glkyqeg5i.pdf

Long-term organic farming fosters below and aboveground biota: Implications for soil quality, biological control and productivity

BACKGROUND
The health benefits of organic foods are unclear.


PURPOSE
To review evidence comparing the health effects of organic and conventional foods.


DATA SOURCES
MEDLINE (January 1966 to May 2011), EMBASE, CAB Direct, Agricola, TOXNET, Cochrane Library (January 1966 to May 2009), and bibliographies of retrieved articles.


STUDY SELECTION
English-language reports of comparisons of organically and conventionally grown food or of populations consuming these foods.


DATA EXTRACTION
2 independent investigators extracted data on methods, health outcomes, and nutrient and contaminant levels.


DATA SYNTHESIS
17 studies in humans and 223 studies of nutrient and contaminant levels in foods met inclusion criteria. Only 3 of the human studies examined clinical outcomes, finding no significant differences between populations by food type for allergic outcomes (eczema, wheeze, atopic sensitization) or symptomatic Campylobacter infection. Two studies reported significantly lower urinary pesticide levels among children consuming organic versus conventional diets, but studies of biomarker and nutrient levels in serum, urine, breast milk, and semen in adults did not identify clinically meaningful differences. All estimates of differences in nutrient and contaminant levels in foods were highly heterogeneous except for the estimate for phosphorus; phosphorus levels were significantly higher than in conventional produce, although this difference is not clinically significant. The risk for contamination with detectable pesticide residues was lower among organic than conventional produce (risk difference, 30% [CI, -37% to -23%]), but differences in risk for exceeding maximum allowed limits were small. Escherichia coli contamination risk did not differ between organic and conventional produce. Bacterial contamination of retail chicken and pork was common but unrelated to farming method. However, the risk for isolating bacteria resistant to 3 or more antibiotics was higher in conventional than in organic chicken and pork (risk difference, 33% [CI, 21% to 45%]).


LIMITATION
Studies were heterogeneous and limited in number, and publication bias may be present.


CONCLUSION
The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods. Consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.


PRIMARY FUNDING SOURCE
None.

Are organic foods safer or healthier than conventional alternatives? a systematic review

Background The health benefits of organic foods are unclear. Purpose To review evidence comparing the health effects of organic and conventional foods. Data sources MEDLINE (January 1966 to May 2011), EMBASE, CAB Direct, Agricola, TOXNET, Cochrane Library (January 1966 to May 2009), and bibliographies of retrieved articles. Study selection English-language reports of comparisons of organically and conventionally grown food or of populations consuming these foods. Data extraction 2 independent investigators extracted data on methods, health outcomes, and nutrient and contaminant levels. Data synthesis 17 studies in humans and 223 studies of nutrient and contaminant levels in foods met inclusion criteria. Only 3 of the human studies examined clinical outcomes, finding no significant differences between populations by food type for allergic outcomes (eczema, wheeze, atopic sensitization) or symptomatic Campylobacter infection. Two studies reported significantly lower urinary pesticide levels among children consuming organic versus conventional diets, but studies of biomarker and nutrient levels in serum, urine, breast milk, and semen in adults did not identify clinically meaningful differences. All estimates of differences in nutrient and contaminant levels in foods were highly heterogeneous except for the estimate for phosphorus; phosphorus levels were significantly higher than in conventional produce, although this difference is not clinically significant. The risk for contamination with detectable pesticide residues was lower among organic than conventional produce (risk difference, 30% [CI, -37% to -23%]), but differences in risk for exceeding maximum allowed limits were small. Escherichia coli contamination risk did not differ between organic and conventional produce. Bacterial contamination of retail chicken and pork was common but unrelated to farming method. However, the risk for isolating bacteria resistant to 3 or more antibiotics was higher in conventional than in organic chicken and pork (risk difference, 33% [CI, 21% to 45%]). Limitation Studies were heterogeneous and limited in number, and publication bias may be present. Conclusion The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods. Consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria. Primary funding source None.

Are Organic Foods Safer or Healthier Than Conventional Alternatives?: A Systematic Review

Consumers have become more aware of healthy and safe food produced with low environmental impact. Organic agriculture is of particular interest in this respect, as manifested by 5.768 million hectares managed pursuant to Council Regulation (EEC) 2092/91 in Europe. However, there can be a considerable risk that the avoidance of chemical inputs in organic farming will result in poor food quality. Here the results of a study on the quality of wheat (Triticum aestivum L.) grown in a 21 year agrosystem comparison between organic and conventional farming in central Europe are reported. Wheat was grown in a ley (grass/clover) rotation. The 71% lower addition of plant-available nitrogen and the reduced input of other means of production to the organic field plots led to 14% lower wheat yields. However, nutritional value (protein content, amino acid composition and mineral and trace element contents) and baking quality were not affected by the farming systems. Despite exclusion of fungicides from the organic production systems, the quantities of mycotoxins detected in wheat grains were low in all systems and did not differ. In food preference tests, as an integrative method, rats significantly preferred organically over conventionally produced wheat. The findings indicate that high wheat quality in organic farming is achievable by lower inputs, thereby safeguarding natural resources.

Wheat quality in organic and conventional farming: results of a 21 year field experiment

These proceedings document the results of the congress 'Improving Sustainability in Organic and Low Input Food Production Systems' which took place on March 20–23, 2007, at the University of Hohenheim in Germany. This congress was the 3rd in a series organized as part of the EU funded Integrated Project 'Quality Low Input Food' QLIF . 
The congress was convened in parallel with the 9th Scientific Conference on Organic Agriculture in German-speaking countries, entitled 'Between tradition and globalization', hosted by the University of Hohenheim. 

The QLIF project aims to improve quality, ensure safety and reduce cost along the organic and low input food supply chains through research, dissemination and training activities. Its subprojects cover all aspects of organic and low input food and farming: Consumer studies, quality, crop & livestock production, processing and supply chains, environmental and socioeconomic aspects.

Improving Sustainability in Organic and Low Input Food Production Systems. Proceedings of the 3rd International Congress of the European Integrated Project Quality Low Input Food (QLIF). University of Hohenheim, Germany, March 20 – 23, 2007

In Switzerland, transplants for organic vegetable growing have been fertilised traditionally with slaughterhouse by-products. In autumn 2000, the Swiss government restricted the use of such products because of the BSE crisis. To maintain the production of organic transplants, alternative fertilisers needed to be tested. Eleven alternatives to horn powder (standard fertiliser) were selected based on the organic standards of the European Union, including feather powder (as an animal based product without BSE risk). The products were mixed with a standard growing media for organic transplants in a concentration of 300 mg nitrogen L-1 growing media. Different experiments where set up with head lettuce (Lactuca sativa), Chinese cabbage (Brassica rapa var. pekinensis) and fennel (Foeniculum vulgare), at two different planting times: immediately after mixing the growing media and six weeks after mixing, in heated and cold greenhouses. Beside weight per plant, we assessed phytotoxic effects 0, 2, 4 and 6 weeks after mixing the media, and mineralised nitrogen in the growing media. When planting immediately after mixing, potato protein, vinasse (wastes of food processing), and feather powder resulted in the highest weight per plant. Plants fertilised with horn powder, sunflower oil cake and ground field beans had the lowest weight per plant (40% less). Horn powder, ground malt sprouts, vinasse, potato protein and feather powder with stored growing media produced the strongest transplants. Phytotoxicity tests (four different methods) showed significant differences between horn powder (slight damage) and field beans (seriously harmed). Horn powder is still the best fertiliser for organic transplant production followed by feather powder. Horn powder causes little phytotoxicity to the crop even under extreme conditions. The most promising pure plant products are potato protein, malt sprouts and vinasse. Plant-based fertilisers need to be applied carefully; the fertiliser should be mixed with the growing media at least two weeks before sowing.

A Comparison of Plant and Animal Based Fertiliser for the Production of Organic Vegetable Transplants

Zusammenfassung der Studie: 

Die vorliegende Literaturarbeit ist Bestandteil eines von Coop Schweiz mitfinanzierten Qualitatsprojektes am FiBL und hat zum Ziel, den Stand der vergleichenden Qualitatsforschung anhand von neueren Arbeiten darzustellen, die in zwei kurzlich erschienenen Literaturstudien (Woese et al. 1997, Worthington 1998) noch nicht erfasst sind. 

Insgesamt wurden 33 Studien ausgewertet. Davon konnen 19 Arbeiten als Vergleichsuntersuchungen zwischen bio und konventionell im engeren Sinn gewertet werden. Die restlichen Ergebnisse stammen aus Dungungs- und aus Sortenversuchen.

17 Arbeiten sind unseres Erachtens fur die Qualitatsforschung von geringer Bedeutung. Neun Studien haben wir als mittel und sechs Arbeiten als wertvoll beziehungsweise als prufenswert eingestuft. Unter den gesichteten Arbeiten befindet keine, die uns als richtungsweisend beziehungsweise mit wesentlich neuen Erkenntnissen fur die Qualitatsforschung erscheint. 

Einige der hier ausgewerteten Arbeiten zeigen, dass Bioprodukte im Vergleich zu konventionellen gunstigere Werte bei den Nitrat, Schwermetall- und Vitamingehalten aufweisen. Da es sich dabei jedoch oft um relativ kurzfristige Untersuchungen handelt, durfen diese Resultate nicht verallgemeinert werden. Ungunstigere Ergebnisse fur biologisch angebaute Produkte ergaben sich nur in Einzelfallen. Eine grosse Anzahl von Untersuchungen stellte keine relevanten Unterschiede zwischen den Anbausystemen fest. Generell haben die Tatigkeiten auf dem Gebiet der vergleichenden Qualitatsforschung im Vergleich zu den siebziger und achziger Jahren abgenommen. 

Als neue methodische Ansatze sind die Berechnung eines Qualitatsindexes zur Integration zahlreicher Einzelergebnisse, sowie erste Untersuchungen uber die Spermienkonzentration unterschiedlich ernahrter Manner zu nennen. Grundlagenarbeiten uber die Eignung, Reproduzierbarkeit oder Variabilitat namentlich im Bereich der sogenannten ganzheitlichen Methoden (P-Wert, Biophotonen und Selbstzersetzungstest) fehlen weitgehend. Am haufigsten und am erfolgversprechendsten zur Differenzierung von Anbaumethoden wurden – wie bereits in den vorangegangenen Literaturarbeiten – die bildschaffenden Methoden eingesetzt. Die wenigen Ergebnisse, die zu den alternativen Qualitatserfassungsmethoden vorliegen, lassen nach wie vor keinen eindeutigen Schluss zu, inwiefern diese Methoden zur Qualitatsdifferenzierung tatsachlich geeignet sind.

Mit den derzeitig zur Verfugung stehenden Untersuchungsmethoden kann gezeigt werden, dass die biologische Bewirtschaftungsweise – mit einem deutlich geringeren Hilfsmitteleinsatz – gleichwertige und in Einzelfallen sogar gunstigere Produktqualitaten erreicht. Weitere Anstrengungen sind aber notig, um das von Konsumenten und Konsumentinnen in Befragungen am haufigsten genannte Kaufmotiv “hoherer Gesundheitswert von Bioprodukten” wissenschaftlich zu belegen.

/pdf/vergleichende-qualitatsuntersuchungen-zwischen-biologisch-16z9se4grk.pdf

Vergleichende Qualitätsuntersuchungen zwischen biologisch und konventionell angebauten Produkten: Eine kritische Betrachtung der Forschungsarbeiten zwischen 1993 und 1998.

In den vergangenen Jahren wurde die Methode der Okobilanzierung weiterentwickelt und an die Bedurfnisse der Landwirtschaft angepasst. Mit vergleichenden Okobilanzen wurden bereits bisher die Umweltauswirkungen der biologischen und integrierten Anbauweise erfasst. Diese Arbeiten beschranken sich jedoch auf die Ebene der Einzelkultur. Im vorliegenden Beitrag stellen wir vergleichende Okobilanzen uber eine ganze Fruchtfolgeperiode vor, die wir im Rahmen eines langjahrigen Vergleichsversuches (DOK-Versuch) durchfuhrten. Unter diesen Bedingungen schnitt das organisch- biologische Verfahren okologisch besser ab als das konventionelle/integrierte.

Thomas Alföldi

Papers

Wheat quality in organic and conventional farming: results of a 21 year field experiment

Improving Sustainability in Organic and Low Input Food Production Systems. Proceedings of the 3rd International Congress of the European Integrated Project Quality Low Input Food (QLIF). University of Hohenheim, Germany, March 20 – 23, 2007

A Comparison of Plant and Animal Based Fertiliser for the Production of Organic Vegetable Transplants

Vergleichende Qualitätsuntersuchungen zwischen biologisch und konventionell angebauten Produkten: Eine kritische Betrachtung der Forschungsarbeiten zwischen 1993 und 1998.

IP- und Bio-Produktion: Ökobilanzierung über eine Fruchtfolge