Table 2.
Summary of parameter comparison between the study sites
| Dependent variable | Test | Test statistic | P | Reference site | Test site |
|---|---|---|---|---|---|
| Land cover | |||||
| Total OSR at Core area | 614.6 ha | 791.7 ha | |||
| Median OSR field size | Wilcoxon rank sum test | W = 170 | 0.999 | 33.5 ha | 35.3 ha |
| Percentage OSR of arable land | 32.3 % | 28.5 % | |||
| Percentage arable land | 49.5 % | 72.2 % | |||
| Soil characterisation of OSR fields | |||||
| pH | Linear mixed model | F1, 33 = 3.79 | 0.060 | 6.33 ± 0.72 | 6.15 ± 0.44 |
| Total organic carbon | Linear mixed model | F1, 33 = 3.92 | 0.056 | 1.02 ± 0.24 % | 0.88 ± 0.20 % |
| Water holding capacity/100 g dry matter | Linear mixed model | F1, 33 = 3.71 | 0.063 | 28.5 ± 2.0 g | 26.9 ± 2.6 g |
| Soil type | Fisher’s exact test | 0.093 | 98.3 % loamy sand | 98.7 % loamy sand | |
| Climatic conditions at study locations during exposure phase | |||||
| Daily mean temperature | Linear mixed model | F10, 335 = 0.19 | 0.669 | 12.3 ± 2.4 °C | 12.2 ± 2.6 °C |
| Daily mean of relative humidity | Linear mixed model | F10, 335 = 0.50 | 0.497 | 77.9 ± 9.3 % | 78.5 ± 9.3 % |
| Daily sum of precipitation | Linear mixed model | F10, 335 = 0.12 | 0.739 | 1.4 ± 2.2 mm | 1.3 ± 3.1 mm |
| Daily mean wind speed | Linear mixed model | F10, 308 = 0.62 | 0.449 | 1.4 ± 0.7 m/s | 1.5 ± 0.7 m/s |
| Agronomic practice | |||||
| Flowering time of OSR varieties by crop area | Early | 17.6 % | 50.5 % | ||
| Medium | 68.6 % | 32.1 % | |||
| Late | 13.8 % | 17.3 % | |||
| Thousand seed weight | General linear model | F1, 32 = 1.63 | 0.211 | 6.86 ± 1.32 g | 5.92 ± 1.21 g |
| Drilling rate | Student’s t-test | t = −3.40 | 0.002 | 2.8 ± 0.8 kg/ha | 3.6 ± 1.1 kg/ha |
| Drilling rate weighed by crop area | General linear model | F1, 65 = 0.52 | 0.474 | 2.6 ± 1.3 kg/ha | 2.7 ± 1.7 kg/ha |
| OSR seeds/m2 | Wilcoxon rank sum test | W = 304.0 | <0.001 | 39.6 ± 7.4 | 50.8 ± 14.2 |
| Total number of insecticide spray applications | Wilcoxon rank sum test | W = 192.5 | 0.021 | 4.8 ± 0.4 | 4.1 ± 0.9 |
| Number of insecticide spray applications in autumn 2013 | Wilcoxon rank sum test | W = 195.5 | 0.016 | 1.4 ± 0.8 | 0.9 ± 0.25 |
| Number of insecticide spray applications in spring 2014 | Wilcoxon rank sum test | W = 152.0 | 0.543 | 3.4 ± 0.5 | 3.1 ± 0.9 |
| OSR development | |||||
| Date of OSR drilling | ANOVA | F1, 33 = 1.09 | 0.305 | 18 August 2013 ± 2.5 days | 19 August 2013 ± 4.4 days |
| OSR emergence rate | Wilcoxon rank sum test | W = 669.5 | 0.800 | 68 ± 21 % | 68 ± 28 % |
| OSR plant density | Wilcoxon rank sum test | W = 391.5 | 0.004 | 26.0 ± 7.3 plants/ m2 | 32.6 ± 11.4 plants/m2 |
| OSR development (BBCH stages) | ANOVA | F1, 232 = 0.00 | 0.972 | ||
| OSR yield | General linear model | F1, 33 = 8.08 | 0.008 | 33.9 ± 7.1 dt/ha | 38.6 ± 6.3 dt/ha |
| Clothianidin | |||||
| Residues in soil before drillinga | Linear mixed model | F1, 33 = 0.53 | 0.470 | 1.9 ± 1.1 μg/kg | 2.3 ± 1.5 μg/kg |
| Loading of OSR seeds | Linear mixed model | F1, 32 = 439 | <0.001 | 0.06 ± 0.07 g/kg | 7.8 ± 1.5 g/kg |
| Application rate | Linear mixed model | F1,32 = 83.9 | <0.001 | 0.19 ± 0.25 g/ha | 28.8 ± 10.0 g/ha |
Mean values are given ± standard deviation. For parameters without test statistic, only descriptive analyses were performed
a Calculating with upper limits of 1.5 μg/kg for determined concentrations <LODsoil and 5 μg/kg for <LOQsoil