Table 2.
Optimal intensities for the trials conducted during 2007–2009 (cf. Table 1) and their effects on selectivity (calculated crop soil cover corresponding to 80% weed control) and yield response (calculated crop soil cover and weed control that attained yield gain). Ranges of crop leaf cover, weed density and soil density in the untreated plots were used as data source to develop the decision making based method for automatic harrowing.
| Crop growth stage (BBCH) | Crop leaf cover (%) | Weed density (plants m−2) | Soil density (Newton) | Intensity† | Crop Soil Cover (%) corresponding to 80%weed control | Crop Soil Cover (%) that attained yield gain | Weed control (%) that attained yield gain | Yield gain (%) |
|---|---|---|---|---|---|---|---|---|
| Experiment 1 | ||||||||
| (12) | nd | 40–56 | nd | strong | 24 | 94 | 19 | |
| (14) | 18–20 | 82–93 | nd | strong | 47–50 | 15 | 41 | 16 |
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| Experiment 2 | ||||||||
| (24) | 24–27 | 31–41 | nd | lightest | 7–16 | 11 | 80 | −3 |
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| Experiment 3 | ||||||||
| (15) | 3–5 | 58–73 | 107–147 | strongest | 22–30 | 36 | 90 | 37 |
| (21) | 8–11 | 148–250 | 101–142 | strongest | 22–30 | 28 | 91 | 45 |
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| Experiment 4 | ||||||||
| (24) | 5–9 | 23–25 | light | 16–31 | 0 | |||
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| Experiment 5 | ||||||||
| (14) | 4–6 | 28–63 | 9–20 | strong | 40–50 | nd | nd | nd |
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| Experiment 6 | ||||||||
| (12) | 6–7 | 58–147 | nd | light | 22–30 | 25 | 90 | 16 |
| (15) | 17–19 | 147–154 | nd | strong | 40–48 | 50 | 80 | 5 |
†
Tine angles: lightest = 61°, light = 41°, strong = 28°, strongest = 4°;
nd = data could not be assessed.