Microbial response of soils with organic and conventional management history to the cultivation of Bacillus thuringiensi
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ORIGINAL PAPER
Microbial response of soils with organic and conventional management history to the cultivation of Bacillus thuringiensis (Bt)-maize under climate chamber conditions Andreas Fließbach & Bruno Nietlispach & Monika Messmer & Ana-Sue Rodríguez-Romero & Paul Mäder
Received: 23 July 2012 / Revised: 18 December 2012 / Accepted: 9 January 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract An experiment was carried out in a climate chamber to analyse if Bt-maize may cause particular changes in soils with different levels of microbial biomass and activity due to long-term management history. Among the soils selected, the ones managed organically for 30 years exhibited twice the microbial biomass and 2.6 times the dehydrogenase activity (DHA) of the soil from a field with long-term conventional maize monoculture. Soils were cultivated twice in a row with Bt-maize, its near-isogenic line and a conventional breeding line. We tested the hypotheses that (a) soil microbial biomass and activity are affected by the cultivation of Bt-maize and that (b) the influence of Btmaize depends on the level of soil microbial biomass and activity. Shoot and root yield and shoot C-content of Btmaize were higher than the ones of the near-isogenic line. DHA under Bt-maize was 6 % higher, and the metabolic quotient for CO2 (qCO2) was 9 % lower than under its nearisogenic line, giving some support to hypothesis (a). No significant interactions of the soils and the varieties used were found in this study, thus hypothesis (b) was not
A. Fließbach (*) : B. Nietlispach : M. Messmer : A.-S. Rodríguez-Romero : P. Mäder Research Institute of Organic Agriculture (FiBL), Ackerstrasse, Postfach 5070, Frick, Switzerland e-mail: [email protected] URL: www.fibl.org A.-S. Rodríguez-Romero Instituto Canario de Investigaciones Agrarias (ICIA), Apdo. 60. 38200, La Laguna, Tenerife, Spain
confirmed, and soils with different microbial biomass and activity appear to react in a similar way to the cultivation of Bt-maize. Keywords Bt-maize . Soil fertility . GMO . Microbial biomass . Soil respiration . Dehydrogenase activity . Mycorrhiza
Introduction Agricultural management may affect soil quality by the use of organic matter inputs, improved crop rotations and conservation tillage (Hobbs et al. 2008). Stabilising soils and their fertility is an important goal for farmers, who aim at conserving the productivity of their land for future generations. Organic agriculture is building on recycling of nutrients, bio-control and mechanical weeding strategies and exacerbated positive impact on soils, biodiversity and landscapes (Bengtsson et al. 2005; Hole et al. 2005; Mäder et al. 2002). The implementation of conservation agriculture with positive effects on soil quality has been enabled by the invention of new machinery, selective herbicides and genetically modified (GM) crop varieties tolerant to broadspectrum herbicides (Dill et al. 2008; Triplett and Dick 2008) that alleviate direct drilling. The combination of both, organic farming and c
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