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

Abstract

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.

Emergence dynamics of barnyardgrass and jimsonweed from two depths when switching from conventional to reduced and no-till conditions

“…By developing such DSS, a decision-making process that will determine ''if'', ''how'' and ''when'' weed control is needed can be established, thus optimizing the time of weed control while reducing redundant herbicide applications or mechanical interventions (Masin et al, 2011;Vasileiadis et al, 2011). There is considerable information on emergence timing of cool temperate weed species (e.g.…”

“…However, what are the implications switching from conventional to reduced or no tillage systems in terms of weed seedbank dynamics? Inversion tillage through moldboard plowing reduces weed populations by burying a large proportion of freshly shed seeds deep in the soil profile (Vasileiadis et al, 2007). Conversely, chisel plowing retains them nearer the surface facilitating germination and emergence, thereby increasing the requirement of management inputs to control them (Ball, 1992;Vasileiadis et al, 2007).…”

“…pre-transplant herbicide and seedbed operations) in late established tobacco (i.e. transplanted end of May) compared to the other spring-sown crops (Vasileiadis et al, 2007(Vasileiadis et al, , 2012.…”

“…Inversion tillage through moldboard plowing reduces weed populations by burying a large proportion of freshly shed seeds deep in the soil profile (Vasileiadis et al, 2007). Conversely, chisel plowing retains them nearer the surface facilitating germination and emergence, thereby increasing the requirement of management inputs to control them (Ball, 1992;Vasileiadis et al, 2007). Other studies indicate that weeds increase after several years of reduced tillage because of increased seed accumulation at the soil surface, the lack of disruption of underground vegetative reproductive organs (Cardina et al, 1991;Bàrberi et al, 1998) and changes in timing of weed emergence compared with inversion tillage (Bullied et al, 2003).…”

“…It is characterized by high productivity, high inputs (i.e. pesticides, fertilizers and water), increased mechanization (Le Féon et al, 2010) and more simplified cropping sequences (Stoate et al, 2001) where the crop choice is often market driven (Vasileiadis et al, 2011). However, the long-term sustainability and environmental effects of the intensification of agricultural systems have raised public concerns in terms of negative consequences (Matson et al, 1997).…”