Validazione di Piani di Disaster Recovery mediante Simulatore

Contribution published online at: http://www.mimos.it/nuovo/contenuto_view.asp?check=10

Reduction in field emergence and seedbank density of Galinsoga quadriradiata and other weeds after contrasting false seedbed strategies in organic vegetable fields

Mechanical weed control in low competitive, organic vegetable production systems is challenging, particularly in fields with large populations of Galinsoga spp. (Asteraceae). Various false seedbed techniques are used prior to crop planting or sowing to prevent weed emergence, albeit with variable success. This study investigated the impact of machinery type (flamer, hoe and harrow), number of passes (2 and 4), tillage depth (1-4 cm) and intensity (double and single hoeing, and hoeing with or without additional harrowing) on weed emergence and seedbank density in 0-5 cm topsoil of organic vegetable fields. False seedbed machinery that did not or minimally disturb the soil was most appropriate for preventive control of Galinsoga quadriradiata (Hairy galinsoga) and total weed seeds, with reductions in seedling emergence up to 99% and 73%, respectively, for flaming, and 74% and 67%, respectively, for 1 cm deep hoeing, 1 month after false seedbed creation. Compared with 1 cm deep hoeing, 1 cm deep harrowing was 16% less effective in the control of emerged seedlings, while flaming was highly effective in preventing weed seedling emergence, even after a low number of passes. Tillage intensity was less important than tillage depth for the reduction in weed emergence and seedbank density. Overall, tillage was more effective for seedbank reduction than flaming

Vertical distribution, size and composition of the weed seedbank under various tillage and herbicide treatments in a sequence of industrial crops

Investigations were conducted during the 2003, 2004 and 2005 growing seasons in northern Greece to evaluate effects of tillage regime (mouldboard plough, chisel plough and rotary tiller), cropping sequence (continuous cotton, cotton-sugar beet rotation and continuous tobacco) and herbicide treatment on weed seedbank dynamics. Amaranthus spp. and Portulaca oleracea were the most abundant species, ranging from 76% to 89% of total weed seeds found in 0-15 and 15-30 cm soil depths during the 3 years. With the mouldboard plough, 48% and 52% of the weed seedbank was found in the 0-15 and 15-30 cm soil horizons, while approximately 60% was concentrated in the upper 15 cm soil horizon for chisel plough and rotary tillage. Mouldboard ploughing significantly buried more Echinochloa crus-galli seeds in the 15-30 cm soil horizon compared with the other tillage regimes. Total seedbank (0-30 cm) of P. oleracea was significantly reduced in cotton-sugar beet rotation compared with cotton and tobacco monocultures, while the opposite occurred for E. crus-galli. Total seed densities of most annual broad-leaved weed species (Amaranthus spp., P. oleracea, Solanum nigrum) and E. crus-galli were lower in herbicide treated than in untreated plots. The results suggest that in light textured soils, conventional tillage with herbicide use gradually reduces seed density of small seeded weed species in the top 15 cm over several years. In contrast, crop rotation with the early established sugar beet favours spring-germinating grass weed species, but also prevents establishment of summer-germinating weed species by the early developing crop canopy