Franco P Weibel

Forschungsinstitut für biologischen Landbau, Frick, Aargau, Switzerland

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Publications (9)17.55 Total impact

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    ABSTRACT: To evaluate the influence of compost on soil fertility and plant growth, several medium term and long term field experiments with composts were conducted in different crops. In two maize experiments, one in a sandy and one in a loamy soil, the influence of different composts and digestates on soil parameters and plant growth were investigated. All products increased pH of the soil and improved the biological soil activity (e.g., enzymatic activities). Immature compost immobilized nitrogen and reduced plant growth. Organic nitrogen fertilizer added during cultivation, could compensate the growth depression. A full factorial experiment in a 2-years-old organic apple orchard was conducted from 2001-2007. The factors tested in all 9 possible combinations were: i) biowaste compost, ii) commercial organic N-fertilizer, iii) foliar N-fertilizer. In spring, the highest values for mineralized N (Nmin) in the tree strip were found in the treatment with commercial organic N-fertilizer, with addition of compost it was 75%, and biowaste compost alone reached 50% of this value on average, whereas unfertilized plots had the lowest but still sufficient values for the same tree performance and fruit nutrition as fertilized plots. In the DOK long-term field trial, three farming systems are compared since 1978: i) mineral and organic fertilisers, synthetic pesticides; ii) organic fertilisers, mechanical weeding and biological disease and pest control; and iii) composted manure and bio-dynamic preparations. A conventional system with mineral fertilisers only and an unfertilized treatment serve as controls. Soil fertility mirrored by soil biological parameters, soil biodiversity and soil organic matter are higher in the organic systems and render these systems less dependent from external inputs.
    Acta horticulturae 01/2014; 1018:39-46.
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    ABSTRACT: 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.
    Agronomy for Sustainable Development 01/2013; 33(1). · 3.57 Impact Factor
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    ABSTRACT: Consumers expect organic produce to have higher environmental, health and sensory related qualities than conventional produce. In order to test sensory differences between bio-dynamically, bio-organically and conventionally grown winter wheat (Triticum aestivum L., cv. Runal), we performed double-blinded triangle tests with two panels on dry wholemeal flour from the harvest years 2006, 2007 and 2009 and from two field replicates of the 'DOK' long-term farming system comparison field trial near Basel, Switzerland. Yield and quality parameters were also assessed. Significant farming system effects were found for yield (up to 42% reduction in the organic system), thousand kernel weight, hectolitre weight and crude protein content across the three years. In the triangle tests one out of 12 pair-wise farming system comparisons (PFSCs) on wholemeal flour made from the different wheat samples showed significant sensory differentiation (between bio-dynamically and conventionally grown wheat). When all data from the three harvest years and two panels were aggregated, a statistically significant effect (P = 0.045) of PFSCs on the number of correct answers became evident. Although testing of dry wholemeal flour was very challenging for panellists, we were able to show that sensory differences between farming systems can occur. Copyright © 2012 Society of Chemical Industry.
    Journal of the Science of Food and Agriculture 08/2012; 92(14):2819-25. · 1.76 Impact Factor
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    ABSTRACT: The organic food sales have been increasing during the recent years. It has been hypothesised that organically grown fruits are healthier based on their higher content of phytochemicals. However, data on the bioavailability of phytochemicals from organically or conventionally produced plant foods are scarce. Two human intervention studies were performed to compare the bioavailability of polyphenols in healthy men after ingestion of apples from different farming systems. The administered apples were grown organically and conventionally under defined conditions and characterised regarding their polyphenol content and antioxidant capacity. No significant differences in the polyphenol content and the antioxidant capacity from the organic and conventional farming system were observed. In the short-term intervention study, six men consumed either organically or conventionally produced apples in a randomized cross-over study. After intake of 1 kg apples, phloretin (C (max) 13 + or - 5 nmol/l, t (max) 1.7 + or - 1.2 h) and coumaric acid (C (max )35 + or - 12 nmol/l, t (max) 3.0 + or - 0.8 h) plasma concentrations increased significantly (P < 0.0001) in both intervention groups, without differences between the two farming systems. In the long-term intervention study, 43 healthy volunteers consumed organically or conventionally produced apples (500 g/day; 4 weeks) or no apples in a double-blind, randomized intervention study. In this study, 24 h after the last dosing regime, the apple intake did not result in increasing polyphenol concentrations in plasma and urine compared to the control group suggesting no accumulation of apple polyphenols or degradation products in humans. Our study suggests that the two farming systems (organic/conventional) do not result in differences in the bioavailability of apple polyphenols.
    European Journal of Nutrition 08/2010; 49(5):301-10. · 3.13 Impact Factor
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    ABSTRACT: The present study was performed to evaluate the polyphenol content and antioxidant capacity of apples (cv. ;Golden Delicious') grown under defined organic and conventional conditions. Apples were harvested at five comparable commercial farms over the course of three years (2004-2006). In 2005 and 2006 the antioxidant capacity was 15% higher (p < 0.05) in organically produced apples than in conventionally produced fruits. In 2005 significantly higher polyphenol concentrations were found in the organically grown apples. In 2004 and 2006 no significant differences were observed (2004, 304 +/- 68 microg/g organic vs 284 +/- 69 microg/g conventional, p = 0.18; 2005, 302 +/- 58 micro/g organic vs 253 +/- 41 microg/g conventional, p = 0.002; 2006, 402 +/- 100 microg/g organic vs 365 +/- 58 microg/g conventional, p = 0.17). Year-to-year variations in the antioxidant capacity and the polyphenol content of up to 20% were more significant than the production method found within one year. Finally, flavanols and flavonols were major determinants of the antioxidant capacities in these apples. Overall, the production method had a smaller impact on the variation in the polyphenol content and antioxidant capacity of apples than the yearly climate.
    Journal of Agricultural and Food Chemistry 05/2009; 57(11):4598-605. · 2.91 Impact Factor
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    ABSTRACT: The effects of organic and integrated production systems on the culturable fungal microflora of stored apple fruits from five matched pairs of certified organic and integrated 'Golden Delicious' farms were studied at five representative production sites in Switzerland. Isolated fungi were identified morphologically. Colonization frequency (percentage of apples colonized), abundance (colony numbers), and diversity (taxon richness) were assessed for each orchard. The standard quality of the stored fruits was comparable for both organic and integrated apples and complied with national food hygiene standards. Yeasts (six taxa) and the yeast-like fungus Aureobasidium pullulans were the dominant epiphytes, filamentous fungi (21 taxa) the dominant endophytes. The most common fungi occurred at all sites and belonged to the "white" and "pink" yeasts, yeast-like A. pullulans, filamentous fungi Cladosporium spp., Alternaria spp., and sterile filamentous fungi. Canonical correspondence analysis of the total fungal community revealed a clear differentiation among production systems and sites. Compared to integrated apples, organic apples had significantly higher frequencies of filamentous fungi, abundance of total fungi, and taxon diversity. The effects of the production system on the fungal microflora are most likely due to the different plant protection strategies. The incidence of potential mycotoxin producers such as Penicillium and Alternaria species was not different between production systems. We suggest that higher fungal diversity may generally be associated with organic production and may increase the level of beneficial and antagonistically acting species known for their potential to suppress apple pathogens, which may be an advantage to organic apples, e.g., in respect to natural disease control.
    Microbial Ecology 06/2008; 56(4):720-32. · 3.28 Impact Factor
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    ABSTRACT: The present study was performed to compare the effects on antioxidant activity and on DNA damage of organic and conventionally produced apples grown under controlled conditions in human peripheral blood lymphocytes. Six healthy volunteers consumed either organically or conventionally grown apples (Golden Delicious, 1000 g) from two neighboring commercial farms in a double-blinded, randomized, cross-over study. The average content of total identified and quantified polyphenols in the organically and conventionally produced apples was 308 and 321 microg/g fresh weight, respectively. No statistically significant differences in the sum of phenolic compounds or in either of the polyphenol classes were found between the agricultural methods. Consumption of neither organically nor conventionally grown apples caused any changes in antioxidant capacity of low-density lipoproteins (lag time test), endogenous DNA strand breaks, Fpg protein-sensitive sites, or capacity to protect DNA against damage caused by hydrogen peroxide. However, a statistically significant decrease in the levels of endonuclease III sensitive sites and an increased capacity to protect DNA against damage induced by iron chloride were determined 24 h after consumption in both groups of either organic or conventionally grown apples, indicating the similar antigenotoxic potential of both organically and conventionally grown apples.
    Journal of Agricultural and Food Chemistry 10/2007; 55(19):7716-21. · 2.91 Impact Factor
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    ABSTRACT: Die integrierte und die biologische Obstproduktion haben beide das Ziel, durch die Optimierung aller Kulturmassnahmen und die Berücksichtigung natürlicher Produktionsfaktoren den Einsatz von Hilfsstoffen zu reduzieren und eine umweltschonende Produktion qualitativ hoch stehender Früchte zu erreichen. Die Methoden sind unterschiedlich. In einer Versuchsanlage in Wädenswil wurden die beiden Produktionssysteme möglichst umfassend verglichen. Nach dem ersten Teil mit den Ergebnissen im Bereich Pflanzenschutz werden nachfolgend die anbautechnischen Resultate besprochen. Der Einfluss auf die innere Fruchtqualität und die sensorische Beurteilung folgt im dritten Teil. Schlussfolgerungen: Die IP- und Bio-Bäume zeigten bis zum siebten Standjahr keine eindeutigen Unterschiede im Wachstum. Die Erträge waren im Durchschnitt der vier Sorten in der Bio-Parzelle 15% tiefer als in der IP, vor allem wegen der stärkeren Alternanz der Bio-Bäume. Die Bio- Früchte waren tendenziell kleiner. Die Kalibrierung nach Grösse und Farbe ergab im Mittel der Jahre 1998 bis 2002 (3.–7. Standjahr) keine wesentlichen Unterschiede im Anteil Klasse I. Die Bio-Parzelle wies bei den meisten Nährstoffen höhere Gehalte auf. Der Humusgehalt und die Masse an Boden-Mikroorganismen waren ebenfalls in der Bio-Parzelle höher, obwohl die Baumstreifen nur in den letzten eineinhalb Jahren vor der Analyse unterschiedlich bearbeitet wurden.