The Effect of Bt-corn on Soil Invertebrates, Soil Microbial Community and Decomposition Rates of Corn Post-Harvest Residues Under Field and Laboratory Conditions

ABSTRACT

Effects of Bt corn on post-harvest residues' decomposition, soil microflora, and soil fauna were studied in two field experiments in the Czech Republic. At each experiment location, Bt corn and a non-Bt conventional corn hybrid with a similar genetic background were each planted on half of a field, which was repeated at both locations for 3 years. Field microcosms containing litter bags of Bt or non-Bt corn post-harvest residues and matching field soils were exposed in field plots in completely randomized blocks and sampled after 3, 6, and 18 months. Decomposition of litter bag content, microbial biomass, PLFA profile, and abundance of soil fauna in whole microcosms were determined. No significant effects of Bt corn were recorded for the investigated parameters. In the laboratory, either fresh post-harvest residues or post-harvest residues exposed to soil for 90 days from the above field experiment were used to study the effect of Bt corn on population growth of Enchytraeus crypticus (Oligochaeta: Enchytraedae). Significant (about 30%) reductions of E. crypticus population growth in fresh Bt corn litter in comparison with non-Bt corn were observed. However, this was not observed in litter exposed to soil for 90 days. In conclusion, Bt corn may have a deleterious effect on decomposers in the laboratory, but this effect was minor and restricted to the initial stages of decomposition and undetectable in long-term field experiments.

KEYWORDS:

• Bt corn
• soil biology
• decomposition

Authors thank to the Ministry of Agriculture of the Czech Republic for support, grant no 1B53043.

Notes

Oravecz, O., D. Elhottová, V. Krištfek, V. Šustr, J. Frouz, J. Tříska, and K. Márialigeti. 2004. Application of ARDRA and PLFA analysis in characterizing the bacterial communities of the food, gut and excrement of saprophagous larvae of Penthetria holosericea (Diptera: Bibionidae): a pilot study. Folia Microbiologica. 49: 83–93.