Browsing by Subject "Pesticide free"

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Integrated weed management in a pesticide free area
(2023) Saile, Marcus; Gerhards, Roland
Weed control is a challenging task for farmers in highly specialized crop production systems. The competition of weeds for light, nutrients and water causes significant yield losses. Chemical weed control is still the standard method in European cropping systems. Due to their high selectivity and efficacy against a wide range of weed species, herbicides provide the most efficient weed control in most crops. However, negative impact of herbicides on the environment, loss of biodiversity, possible risks to consumers due to residues in food chain and the increase and spread of herbicide-resistant species force farmers to reduce herbicide use and call for alternative weed control methods. Mechanical weed control methods including hoeing and harrowing represent the most promising alternative direct weed control methods. Weed control costs for mechanical methods are still higher than for herbicides and weed control efficacy is often lower with less than 80 % compared to around 95 % for herbicides. The efficacy of mechanical weed control is dependent on external factors such as soil water content, soil texture, and weed species diversity in the particular field. Herbicides can therefore not be replaced by a single mechanical weed control method. It needs an Integrated Weed Management (IWM) strategy including preventive and direct methods of weed suppression. In this study, IWM were investigated for typical arable farming systems in Southwestern Germany. Studies for this thesis were conducted from 2017 to 2022. The objectives of the thesis were to combine preventive and curative methods of weed control in diverse cropping systems and to improve mechanical weed control methods by precision farming technologies. The results of the thesis have been published in five papers. The first article addressed the effects of preventive weed control by stubble tillage, cover cropping, and the use of glyphosate treatments against Alopecurus myosuroides and volunteer cereals. In two field trials at two sites, cover crop mixtures achieved equal weed control efficacy of up to 100 % as the dual glyphosate treatment. Stubble tillage practices resulted in lower control but caused the highest energy consumption. The second article focused on the effect of two seeding dates (early-, delayed-sowing) and different herbicide strategies on A. myosuroides control on winter cereals. This study was conducted over three years at three locations. Delayed sowing reduced weed emergence by 30-40 %. Delayed sowing in combination with the pre-emergence herbicide cinmethylin provided equal weed control efficacy as a combination of pre-emergence and post-emergence herbicides. The third article focused on the control of A. myosuroides including the combination of integrated stubble management and various application rates of the pre-emergence herbicide cinmethylin. In four field trials over a two-year period, the pre-emergence herbicide cinmethylin was applied at two application rates at two sites. Control success of up to 100 % was achieved through the combination of inversion tillage, false-seedbed preparation and the reduced rate of cinmethylin. The results also showed a high variation of the effect of preventive measures. The fourth article deals with IWM in spring oats and winter wheat. Field experiments were conducted at two locations over two years in five field trials. Chemical weed control was combined with sensor-based mechanical weed control. Data showed that sensor-based mechanical weed control (hoeing and harrowing) in the field trials achieved equal weed control efficacy of up to 100 %. However, highest grain yields were recorded for the combination of pre-emergence herbicide and post-emergence mechanical weed control. The last article dealt with a new cultivation system without chemical synthetic pesticides but with mineral fertilizers (MECS). The hypothesis was that MECS would increase the competitiveness of the crop on the weeds and generate higher yield benefit compared to the organic cultivation system. Field trials were conducted at four sites over two years. Three different cropping systems, an organic cropping system managed according to organic farming guidelines, a conventional cropping system and a MECS, were compared in a 5-year crop rotation. After two years of studies, no clear conclusion can be made how MECS affects the interaction of crops and weeds. Weed control efficacy in MECS was lower than organic farming. The increase in weed pressure in MECS will cause problems in the subsequent crops. Yields were significantly higher in MECS compared to the organic system and only slightly lower than in the conventional system. It can be concluded from these studies that IWM in combinations with precision farming technologies for mechanical weeding can replace herbicides. However, weed control costs were higher with non-chemical weed control methods.