Browsing by Person "Weber, Jonas Felix"

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A study of integrated weed control strategies for establishing soybean (Glycine max L. MERR.) in the German production system
(2017) Weber, Jonas Felix; Gerhards, Roland
Soybean (Glycine max L. MERR.) has expanded to become one of the most traded agriculture products worldwide in recent decades. Europe is one of the primary importing regions; however, the dependence on soybean imports has been critically assessed by the public. To reduce the dependency on soybean imports, increased local soybean production should be favoured. In addition to environmental conditions, weeds are a major limiting factor for soybean yield under German climate conditions. Weeds can be successfully controlled with herbicides, although crop injury frequently occurs after application. Sensor-based screening would be helpful for a rapid evaluation of cultivar tolerance to herbicide application. Alternatively, mechanical weed control strategies can be applied. Since soybean production is currently introduced to the regional crop production, weed control efficiency of conventional mechanical tools (e.g., hoeing and harrowing) have to be evaluated. By using automatic guiding systems intra-row elements could be utilised to increase the weed control efficiency of mechanical hoeing. Other than that, agronomical practices such as the tillage system or cover crops influences the occurrence of weeds. The most common practise worldwide for soybean cultivation is the no-tillage system, which has not yet been investigated under local conditions. Therefore, different weed control strategies in soybean production were investigated according to the following major objectives of this thesis: - Detection of crop injury by herbicides using a chlorophyll fluorescence imaging sensor for different soybean cultivars. - Evaluation of the conventional mechanical strategies of hoeing and harrowing in soybean. - Examination of the weed control efficiency in inter- and intra-row areas using RTK-GNSS precision steering and an optical camera guiding system for mechanical weed control in soybean. - Evaluation of the efficiency of ‘tillage’, ‘reduced tillage’ and ‘no- tillage’ cultivation systems and the influence of cover crops on weed suppression in local soybean production. The Imaging-PAM-sensor based on chlorophyll fluorescence imaging was utilised to investigate the response of different soybean cultivars to the application of herbicides. The measurements indicated significant differences with respect to injury to the cultivars after herbicide application. Herbicides containing the active ingredient ‘metribuzin’ resulted in significant differences in the level of crop injury depending on the cultivar. The active ingredients ‘dimethenamid’ and ‘clomazone’ resulted in less injury, independent of the cultivar. The PAM-sensor was able to detect stress symptoms 3 to 7 days before visual symptoms appeared. An investigation of hoeing and harrowing, which are conventional mechanical techniques for weed control, showed 78% and 72% weed control efficiency, respectively. In further experiments, the results of precision steering systems using RTK-GNSS and an optical camera guiding system additionally equipped with intra-row elements (e.g., finger weeders) were compared with the results of conventional hoeing. Mechanical weed control using automatic steering technology and an intra-row element (finger weeder) reduced the weed density by 89% compared with 68% in the conventional hoeing system. With respect to crop yields, statistical benefits of precision steering were not observed. However, the driving speed could be increased from 4 km h−1 in the conventional hoeing system to 10 km h−1 using the automatic steering systems. In an additional experiment, two cover crops species, rye (Secale cereale L.) and barley (Hordeum vulgare L.), were grown for preventive weed control in soybean production. The cover crops were transformed into a mulch layer using a roller-crimper immediately before soybean was sown using a no-tillage technique. Conventional tillage was performed to compare the systems with respect to their weed control efficiency, crop development and soybean yield. The results showed that the no-tillage system had a greater effect on suppressing summer annual weed species (Chenopodium album (L.), Echinochloa crus-galli (L.) P. Beauv. and Amaranthus retroflexus (L.)) than the tillage systems. Conventional tillage and reduced tillage showed increased suppression of the weed species Matricaria inodora (L.), Stellaria media (L.) Vill. and Sonchus arvensis (L.), which were present in the no-tillage system. However, in the conventional tillage and reduced tillage systems, an additional weed control treatment was necessary to suppress the summer annual weeds and ensure high yields. The cover crop rye resulted in weed control similar to that of barley in the no-tillage system. Despite the low weed density, the no-tillage system with a rolled cover crop showed a yield reduced of 47%, whereas the yield of the reduced tillage system was decrease by 23% compared with the conventional tillage system.