Farming intensity and field margin complexity affected post-dispersal weed seed predation by arthropods in sunflower crops

Farming intensity and complexity of field margins adjoining crop fields are expected to affect seed predation levels in annually cropped fields. The impact of both factors was determined in six sunflower fields in the Pisa Plain (Italy). Arthropod seed predation was measured above- and below-ground by comparing the seed removal of two common weeds differing in seed size (small: Amaranthus retroflexus L.; large: Lolium multiflorum Lam.). Seeds were covered with metal grids to exclude rodents, birds, from predation. Farming system intensity defined the largest difference in weed seed predation for both species. The presence of a complex, undisturbed margin adjoining fields increased seed predation only when conventionally managed. Seed predation was higher in field centres than close to field margins. In organic fields, seed predation for both weed species was lower below-ground than above-ground, whereas the opposite was observed in the other farming systems. Results showed that arthropod predation levels of weed seeds can be encouraged within cropped fields by adopting low-input or organic farming systems or by improving field margin complexity.