Open Access
Table 1.
Effects of cropping system components on the blackgrass life-cycle as simulated by ALOMYSYS (Colbach et al., 2006b; 2007; 2010).
| Cropping system | Intermediate effect | Effect on blackgrass |
|---|---|---|
| Tillage and mechanical weeding | Soil structure | Soil compaction increases mortality of germinated seeds |
| Soil movements = f(soil structure) | Seed burial decreases germination and increases pre-emergent mortality due to insufficient seed reserve. Seeds on soil surface germinate badly because of insufficient seed-soil contact Germinated seeds close to soil surface often die because the top soil dries faster. | |
| Exposes imbibed seeds to light if inverting tool, thus breaking dormancy | ||
| Triggers germination flush if moist soil | ||
| Destroys germinated seeds, seedlings and plants | ||
| Crop | Choice of cultivation techniques | See effects of techniques |
| Occupies space, uses water and nutrients | Decreases components of weed seed production (plant survival, tillers/plant, heads/tiller, flowers/head, seeds/flower) | |
| Seed return to soil seed bank is reduced by crop canopies in multi-annual crops (e.g. grassland, permanent living mulch) | ||
| Sowing date | Crop emergence date | The earlier the weed seedlings emerge relative to the crop, the better they survive and tiller |
| Date of last tillage | The later the last tillage, the more weed seeds have germinated already and are killed by the tillage | |
| Sowing density | Crop density | Increases weed seedling mortality |
| Herbicides | Weed mortality = f(active ingredient, conditions) Weed mortality decreases with plant density, seed depth (for root-acting herbicides) and weed stage | |
Decreases tillering on surviving plants |
||
| Mowing | Destroys tillers and heads. Plants with mature heads die; the remaining tiller again but usually produce less seeds | |
| Nitrogen | Increases flowers/head | |
| Conditions during seed production | Influence dormancy level and germination rates of newly produced seeds | |
| Harvest | Destruction of all plants | |
Each time plants are destroyed, their seed production, if any, is added to the seed bank.
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