Made to measure: Preparing the trial field

The six young scientists stand facing a large dusty field. They intend to set up a total of forty plots on the site. Their equipment consists of tape measures, string, long and short stakes, spray paint and a handcart filled with lime.

First they have to mark out a straight line of several hundred metres along the length of the field. This is then the base line from which the plots will be measured. To ensure that the line is straight, the stakes are aligned. If the line deviates even a little from the stakes, the last plot could easily end up being a few metres out.

The first right-angles also have to be drawn carefully. Tried and tested school knowledge comes in here in the form of Pythagoras’s theorem. Once a start has been made, the work quickly becomes routine: measuring and marking, putting in stakes and pulling string taught. White lines are drawn with lime along the lines marked by the string.

New trial series

A new trial series is starting this year. Over the course of three years, researchers will again be investigating the possible environmental effects of genetically modified Bt maize. The maize being tested in this project possesses multiple pest resistance. It is equally resistant to its main chewing pests, the European corn borer and the Western corn rootworm . The corn borer caterpillars chew through the maize stems, while the Western corn rootworm larvae attack the roots of the maize plants. So far, the only varieties that have been tested are those resistant to one or other of these pests. Newer varieties with ‘stacked genes’ combine the different forms of resistance.

In order to test the environmental compatibility of this Bt maize, it is important to observe both the plant parts above ground and their inhabitants, and the soil and soil organisms.For comparison purposes, a total of three conventional varieties are being grown in this trial series. One of these is the isogenic variety, i.e. the conventional variety from which the Bt maize was developed. On some plots this variety will be treated with a soil insecticide. Previous trials found that insecticide treatment had much more serious consequences for the organisms in the field than the genetic modification. The trial will also look at differences between different varieties, so will involve two other conventional varieties.

Each of the maize variants will be planted on eight plots. They will be arranged according to a randomised plot design, with the different varieties arranged at random but with certain conditions: no two plots with the same variety may be immediately adjacent to each other, and about the same number of plots of each type should be at the edge of the site and in the middle.

Sowing begins

It takes a long afternoon and the following morning of intensive measuring and marking before the trial field is ready. The team has covered several kilometres and their clothes and hair are full of dust.

The sowing can now begin. First, seeds of one of the conventional varieties are sown. Sowing four rows at a time, the tractor moves up and down the plots assigned to this variety.

Meanwhile, others are already carrying out preliminary tests, measuring the density of earthworms at various points on the field. To do this, they dig out a volume of soil defined by a frame, and count the earthworms found in it. In order to assess the impacts of Bt maize on earthworms, there needs to be a fairly high number of them in the field.