Abstract
A cylinder experiment was conducted in northern Greece during 2005 and 2006 to assess emergence dynamics of barnyardgrass (Echinochloa crus-galli (L.) Beauv.) and jimsonweed (Datura stramonium L.) in the case of a switch from conventional to conservation tillage systems (CT). Emergence was surveyed from two burial depths (5 and 10 cm) and with simulation of reduced tillage (i.e. by soil disturbance) and no-till conditions. Barnyardgrass emergence was significantly affected by burial depth, having greater emergence from 5 cm depth (96%) although even 78% of seedlings emerged from 10 cm depth after the two years of study. Emergence of barnyardgrass was stable across years from the different depths and tillage regimes. Jimsonweed seeds showed lower germination than barnyardgrass during the study period, whereas its emergence was significantly affected by soil disturbance having 41% compared to 28% without disturbance. A burial depth x soil disturbance interaction was also determined, which showed higher emergence from 10 cm depth with soil disturbance. Jimsonweed was found to have significantly higher emergence from 10 cm depth with soil disturbance in Year 2. Seasonal emergence timing of barnyardgrass did not vary between the different burial depth and soil disturbance regimes, as it started in April and lasted until end of May in both years. Jimsonweed showed a bimodal pattern, with first emergence starting end of April until mid-May and the second ranging from mid-June to mid-August from 10 cm burial depth and from mid-July to mid-August from 5 cm depth, irrespective of soil disturbance in both cases.
Highlights
Agricultural production worldwide has been intensified in recent decades
Emergence was significantly greater when seeds were buried at 5 cm depth, attaining 96% of emergence compared to 78% from 10 cm burial depth
The interaction between factors showed no significant difference and total emergence of this weed species ranged from 97% at 5 cm depth with soil disturbance to 75% when at 10 cm depth without disturbance
Summary
Agricultural production worldwide has been intensified in recent decades. 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). Intensive tillage operations (i.e. with soil inversion) have been found to adversely affect soil structure and cause excessive breakdown of aggregates, leading to soil erosion in higher rainfall areas (Chauhan et al, 2012), and to have a negative impact on environmental quality by accelerating soil carbon loss and greenhouse gas emissions (Reicosky & Allmaras, 2003). Such concerns provided an incentive to investigate tillage systems that minimize negative impacts on the environment without reducing crop yields. These systems can be broadly termed conservation tillage (CT) systems and involve the reduction or suppression of primary tillage operations such as plowing, disking
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