Testing Coexistence in Practice

2004: How far travels GM maize pollen?

In 2004, farmers in the Federal States of Saxony-Anhalt, Bavaria, Mecklenburg-Western Pomerania, Brandenburg, Thuringia, Saxony and Baden-Württemberg sowed Bt maize on 300 hectares. The accompanying research was coordinated by the Halle-Wittenberg Institute of Plant Breeding and Plant Protection of the Martin Luther University, and was supported by the Federal Ministry for Education and Research.

Leaving questions of biosafety aside, researchers explored parameters relevant to the coexistence of GM and non-GM crops, such as travel distances for maize pollen, and the extent to which conventional fields are affected by GM pollen. During 2004, data were collected for various conditions such as field and farm size, climate, and topography. Researchers ultimately presented recommendations for the cultivation of GM maize, intended to keep out-crossings in neighbouring conventional or organic maize fields below the labelling threshold of 0.9 percent.

For the studies, central parcels of one to twenty hectares were sown with GM maize. These parcels were surrounded by at least 60 metres of conventional maize which, in order to maximise the out-crossing rate, had similar flowering dates.

The researchers found that the first ten metres of conventional maize adjacent to the GM plot regularly exceed a GM share of 0.9 percent.  At distances of twenty metres and more from the GM plot, however, only incidental individual samples exceeded the labelling threshold. Averages taken in all cardinal directions for both grain and silage maize showed GM shares below 0.5 percent, once the distance to the GM maize measured at least 20 metres (below 0.2 percent for 50 metres).

2005: The influence of buffer zones
Since, in practice, two maize fields rarely share a border but are separated by another crop, the accompanying research in 2005 investigated the impact of buffer zones. Do high and low crops have different buffering effects? What role do fallows and roads play? On this occasion, research was led by the University of Rostock Institute for Land Use.

Three different field designs were used. In the first design, one to five hectares of GM maize were completely surrounded by either barley, peas or potatoes, followed by at least 60 metres of conventional maize. In the second design, the buffer crops and the conventional maize were only planted in two directions – upwind and downwind –  with the separating crops being barley, peas, or ryegrass. The third design was similar to the first, but part of the GM plot in the centre was neighboured directly by the conventional maize. The lack of isolation distance allowed better assessment of the impact of the separating crops.

On this occasion, out-crossings exceeding the labelling threshold were found even at distances of more than 20 metres. The new recommendations for the cultivation of GM maize included the use of a buffer strip of 25 metres, consisting of conventional maize that, at harvest, should be treated as GM maize, followed by 50 metres of any other separating crops. The Bavarian Minister of Agriculture even recommended 150 metres as precaution.

Parallel studies on bees found that although pollen collected by bees in the neighbourhood of GM maize exceeded the labelling threshold, no traces of GM maize were found in the honey and remained below the detection threshold of 0.1 percent.

Further coexistence research in 2005 and 2006
The Federal Ministry for Food, Agriculture and Consumer Protection also conducted coexistence research in 2005 and 2006, but no results have been published to date.

See also on GMO-Compass:

• Coexistence: Different Agricultural Systems Working Side by Side