The feasibility of coexistence between GM and non-GM maize was studied under real agronomic conditions. Bt-maize MON810 was planted at nearly 30 field sites in plot sizes ranging from 0.3 to 23 hectares.

The flowering of the two sorts of maize was synchronous. In addition, using additional strips, different planting dates of GM and non-GM maize and an earlier ripening conventional maize were tested to obtain altered flowering and thereby reduce cross-pollination.

Samples were harvested from the conventional maize at 0–10, 20–30, and 50–60 m from the Bt maize sources to assess the GM DNA content in the non-GM plants; wind direction and strength was taken into account

Using samples in all directions from the GM source, no-GM maize further than 10 m from a GM source contained more than 0.9% of GM genetic material, the legal threshold above which a label is required.

The authors conclude that coexistence is actually feasible with a separation distance of 20 m.

Source:

W. E. Weber, T. Bringezu, I. Broer, J. Eder, and F. Holz (2007). Coexistence Between GM and Non-GM Maize Crops – Tested in 2004 at the Field Scale Level (Erprobungsanbau 2004). J. Agronomy & Crop Science, vol. 193, pages 79-92 (http://www.ingentaconnect.com/content/bsc/jac/2007/00000193/00000002/art00001;jsessionid=32reet6gaoakj.alice)

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