*2.2. Sampling*

#### 2.2.1. Sampling of Sugar Beet Plants

Starting four weeks after sowing, sugar beet plant samples were collected every two weeks at all three locations during the two growing seasons (2015 and 2016). In the first four sampling periods, whole plants were collected. From the fifth sampling until the end of the experiment, the collected plants were divided into leaves and roots, which were analyzed separately. The last sampling concerned only the roots. Three samples were taken for each treatment. A total of 432 sugar beet samples were collected and analyzed for neonicotinoid residues. Each sample contained five plants with a minimum weight of 20 g. The collected samples were carefully labeled and transported in portable coolers to an accredited laboratory for analysis.

#### 2.2.2. Sampling of Soil

In order to determine neonicotinoid residues in the soil, two samples were taken once at each site from the depth of a plow layer (30 cm). In 2016, 15 sub-samples (each weighing 1.000 g, depending on field size) were taken, pooled and homogenized at each site, and a subset of the pooled soil samples (20 g) from each treatment area was taken and stored in a freezer until analyzed.
