This article documents the impact of site conditions and farming practices on the occurrence of rare and endangered weeds on arable land in the Czech Republic. A survey was conducted between 2006 and 2008 in winter cereals, spring cereals and wide-row crops. The relationship between the occurrence of plants and explanatory factors was analysed using a multivariate analysis to calculate species frequencies in different types of farming, crops and altitudes. In total, 290 relev es were recorded, with a total number of 172 weed species. Nineteen weeds, classified as rare and endangered species according to the national Czech list, were identified in 106 relev es. The highest effect on the occurrence of rare and endangered weed species was observed for altitude. Almost half of the recorded endangered and rare species belonged to the thermophilous weed vegetation typical for cereals on basic soils. A higher occurrence of endangered species has been confirmed for organic farming, where the sum of frequencies was 4.5 times higher than in conventional farming. Field size was not included in our analyses, but could be a factor affecting weed assemblages. The highest frequency of rare species was recorded in spring cereals, followed by winter cereals and wide-row crops. Higher numbers were identified within fields with higher weed coverage. Lower farming intensity and diversified farming systems at higher altitudes provided better conditions for the occurrence of rare species than intensively farmed lowlands.
There is much documentation in the scientific literature (e.g. Clay et al. 1999, Hamouz et al. 2006, Gerhards et al. 2012) that weeds are distributed in a patchy manner throughout agricultural fields. An aggregated distribution pattern of weed populations provides opportunity to reduce the herbicide application if site-specific weed management is adopted. Gerhards et al. (2002) achieved herbicide savings of 60% and 92% for dicotyledonous and monocotyledonous weeds, respectively, in spring barley (Hordeum vulgare L.) cultivation, and savings of 11% and 81% were achieved for the same weed groups for maize (Zea mays L.). In two winter wheat fields, Häusler et al. (1998) found that herbicide applications were necessary for 24% and 35% of the area for Galium aparine L., for 25% and 31% for other dicotyledonous weeds and for 55% and 7.5% for grasses. Using a simulation, Christensen and Heisel (1998) estimated a 40% reduction of herbicide consumption, and Nordmeyer and Häusler (2000) calculated the need for herbicide application from 7% to 64% of the total area in various fields.Site-specific weed management is based on the threshold concept: the aim is to adjust the intensity of management practices to the actual degree of weed infestation, with only those areas having a weed density exceeding the predefined control threshold typically being treated. However, sitespecific weed management requires the precise setting of control thresholds for effectiveness and reliability. Furthermore, both areas that are treated superfluously and unsprayed areas that will show increases in weed infestation should be Impact of site-specific weed management on herbicide savings and winter wheat yield P. Hamouz, K. Hamouzová, J. Holec, L. Tyšer Department of Agroecology and Biometeorology, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Prague, Czech Republic ABSTRACTAn aggregated distribution pattern of weed populations provides opportunity to reduce the herbicide application if site-specific weed management is adopted. This work is focused on the practical testing of site-specific weed management in a winter wheat and the optimisation of the control thresholds. Patch spraying was applied to an experimental field in Central Bohemia. Total numbers of 512 application cells were arranged into 16 blocks, which allowed the randomisation of four treatments in four replications. Treatment 1 represented blanket spraying and the other treatments differed by the herbicide application thresholds. The weed infestation was estimated immediately before the post-emergence herbicide application. Treatment maps for every weed group were created based on the weed abundance data and relevant treatment thresholds. The herbicides were applied using a sprayer equipped with boom section control. The herbicide savings were calculated for every treatment and the differences in the grain yield between the treatments were tested using the analysis of variance. The site-specific applications provided herbicide savings ...
This paper reports on the within-habitat (α) and on the between-habitat (β) diversity of weed vegetation on arable land in the Czech Republic, influenced by management systems, crops grown and altitude. A phytocoenological survey was conducted from 2006 to 2008 during a vegetation period using relevés that were 100 m 2 in size, placed in the central part of fields. The species richness and the mean Sørensen dissimilarity were calculated. The statistically significant effects of the type of farming and altitude on species richness were recorded. The average species numbers in one relevé reached 9.17 and 21.17 in conventional and organic farming, respectively. In both management systems, an increasing number of species was recorded with increasing altitude. Statistically significant effects of all the variables were observed when evaluating β-diversity. Higher β-diversity was found in conventional farming.
Site-specific weed management (SSWM) methods allow spatially variable treatment of weed populations according to actual weed abundance, thus offering the opportunity for herbicide savings. However, SSWM's effect on weed population dynamics is not sufficiently understood. In this study, SSWM was conducted based on various application thresholds to analyse the effects on crop yield and weed infestation in the succeeding crop. SSWM was used on a 3.07 ha experimental field in winter wheat (2011) and winter oilseed rape (2012). The whole area was split into application cells of 6 × 10 m and abundance of all weed species was evaluated manually in each cell. Four different herbicide treatments were tested. Standard whole-field herbicide application (blanket spraying) was treatment 1. Treatments 2, 3 and 4 comprised SSWM using different thresholds for post-emergent herbicide application. SSWM resulted in savings of post-emergent herbicides ranging from 71.9% to 100%, depending on the application threshold. Differences in winter rape yield among treatments were generally small and statistically insignificant (P = 0.989). Although some minor changes in weed abundances were observable, the experiment showed that none of the site-specific herbicide treatments caused a significant (α = 0.05) increase of weed species abundance compared to the standard treatment.
This work is focused on evaluating the effects of site-specific weed management (SSWM) on weed populations over a 4-year period. SSWM was used on a 3.07 ha experimental field during 2011-2014 in a rotation of winter wheat and winter oilseed rape. The area was split into application cells of 6 × 10 m and weed abundance was evaluated manually in each cell. Four different herbicide treatments were tested. Standard whole-field herbicide application (blanket spraying) was treatment 1. Treatments 2, 3 and 4 comprised SSWM using different thresholds for postemergent herbicide applications. SSWM resulted in herbicide savings of 6.3-100% for Galium aparine, 0-84.4% for other dicotyledonous weeds, and 31.3-90.6% for annual monocotyledonous weeds. SSWM led to significantly increased density of G. aparine and Tripleurospermum inodorum in the final experimental year when compared to the blanket treatment. Negative correlation coefficients between 2011 and 2014 plant densities found in SSWM treatments (−0.237 to −0.401) indicate that Apera spica-venti does not establish a long-term soil seed bank.
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