Comparison of Polygonum aviculare L. seedling survival under different tillage systems in Mediterranean dryland agroecosystems

摘要

Weed community shifts in agroecosystems are influenced by multiple factors. Among them, tillage and crop rotation are very important. Polygonum aviculare survival at early plant stages and biomass and density at harvest time were compared under three tillage systems (conventional, CT; minimum, MT; and no tillage, NT). Field studies were conducted from 1997-1998 to 2000-2001, during a crop rotation (pea-wheat-wheat-barley). The layout of the tillage systems was not randomized, which led to confusion between the tillage effect and the site effect, although all three tillage systems were implemented as of 1993-1994 and the same agricultural practices had been employed in the entire field between 1981-1982 and 1992-1993. Seedling mortality was analysed in two monitored cohorts (2000 and 2001) using a generalized linear model of binomial probability distribution with a complementary log-log link function. Analyses of variance considering tillage system (or site) and block were performed on: (1) aboveground biomass at the harvest time of the four crops; (2) density and mean plant biomass at the end of the first two crops; (3) seedling density registered twice during the 1998-1999 campaign. The expected changes to estimated mortality showed that seedlings under NT had greater probabilities of failure than those growing under the other two tillage systems. These differences were found considering the tillage system apart from the crop and the accumulated precipitation effects, which also strongly affects seedling survival. Density, 1999-2000 biomass and 2000-2001 biomass were different under different tillage systems (P < 0.05), the lowest density occurring under NT and the lowest values of biomass under MT. Mean seedling densities were similar between CT and MT, but both were higher than densities under NT. (C) 2004 Elsevier SAS. All rights reserved.