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Durch die steigende Nachfrage nach nicht-chemischen Ansätzen zur Unkrautregulierung gewinnen mechanische Verfahren an Bedeutung. Für spätgesäte, konkurrenzschwache Kulturen wie Melisse (Melissa officinalis) wird empfohlen, mittels präventiver Bodenbearbeitung, etwa durch vorgezogene Saatbettbereitung („Falsches Saatbett“), Unkrautsamen im Boden wiederholt zur Keimung anzuregen und damit die Diasporenbank vor der Aussaat zu reduzieren. In einem zweifaktoriellen Versuch wurde der Zeitpunkt des Pflugeinsatzes (Herbst- oder Frühjahrsfurche) in Kombination mit vier Intensitäten einer flachen Frühjahrsbearbeitung mittels Kreiselegge herbologisch untersucht. Der Versuch wurde 2019/20 an einem ökologisch und einem konventionell bewirtschafteten Standort im Rheinland angelegt. Vor jedem Bodenbearbeitungsgang wurden Unkrautbonituren durchgeführt. Zusätzlich wurde die Diasporenbank im Oberboden (0-7 cm) an drei Terminen erfasst. Am ökologisch bewirtschafteten Standort war die Unkrautdichte drei Wochen nach Aussaat nach Herbstfurche in den drei- und vierfach gekreiselten Faktorkombinationen signifikant geringer im Vergleich zur Frühjahrsfurche (p = 0,023; p = 0,018). Arten mit leichtem Samengewicht (≤ 0,5 mg) wie Aphanes arvensis, Matricaria chamomilla, Papaver rhoeas, Veronica agrestis und Viola arvensis hatten in den viermal gekreiselten Varianten einen tendenziell höheren Anteil (41,1 % ± 23,6 %) im Vergleich zu einer einmaligen Saatbettbereitung (15,6 % ± 20,8 %). Diese wies tendenziell eine höhere Dichte an Arten mit höherem Samengewicht (> 1 mg) wie Ranunculus repens oder Chenopodium album auf (49,3 % ± 28,2 %). Dies lässt vermuten, dass die Keimung kleinerer Samen bei feineren Bodenaggregaten begünstigt wird. Am konventionell bewirtschafteten Standort wurden bei geringem Samenpotential im Oberboden (< 200 je m2) keine Effekte der Bodenbearbeitung auf Unkrautdichte und Artenzusammensetzung festgestellt. Die Ergebnisse des ersten Versuchsjahres zeigen, dass eine wiederholte flache Frühjahrsbearbeitung an einem Standort mit hohem Samenpotential (> 6000 Samen m-2) nicht zu einer Minderung der Unkrautdichte, jedoch zu einer Selektion eines bestimmten Artenspektrums führen kann.

Flaxseed is the economically most important medicinal plant in Germany. It is cultivated on an area of over 2500 ha. Its pollen and/or nectar are a potential foodresource for insects in intensively used agricultural landscapes. To test this hypothesis insects on flowering flaxseed plants and the flowering environment were collected and the species and their abundance were determined. The study focused on taxa of Hymenoptera (except Formicidae) and Diptera. In addition, pollen samples were taken from wildbees and intestinal content of hoverflies was analyzed. On two out of three study sites we found higher species numbers in flaxseed than in the flowering environment. Further, more individuals of Hymenoptera were found in cultivated flaxseed compared to the neighboring environment on all three sites. Flaxseed pollen was found on Halictus sp. and Lasioglossum calceatum, indicating that these species may serve as pollinators of flax. Moreover, flaxseed pollen was found in the digestive system of Syrphus ribesii which suggests a potential role of flaxseed as a food source for this species.

While intensive control of weed populations plays a central role in current agriculture, numerous studies highlight the multifaceted contribution of weeds to the functionality and resilience of agroecosystems. Recent research indicates that increased evenness within weed communities may mitigate yield losses in contrast to communities characterized by lower diversity, since weed species that strongly affect crop yields, also dominate weed communities, with a concurrent reduction of evenness. If confirmed, this observation would suggest a paradigm shift in weed management towards promoting higher community diversity. To validate whether the evenness of weed communities is indeed linked to higher crop productivity, we conducted two field experiments: one analyzing the effects of a natural weed community in an intercrop of faba bean and oat, and the other analyzing the effects of artificially created weed communities, together with the individual sown weed species, in faba bean, oats and an intercrop of both crops. The evenness of the weed communities ranged from 0.2 to 0.9 in the natural weed community, from 0.2 to 0.7 in faba bean, from 0 to 0.8 in the intercrop and from 0.3 to 0.9 in oats. Neither the natural nor the artificial weed community showed significant effects of evenness on crop grain yield or crop biomass. The results of this study do not validate a positive relationship of crop productivity and weed evenness, possibly due to low weed pressure and the absence of competitive effects but suggest that also less diverse weed communities may be maintained without suffering yield losses. This is expected to have far reaching implications, since not only diverse weed communities, but also higher abundances of few weed species may contribute to ecosystem functions and may support faunal diversity associated with weeds. [ABSTRACT FROM AUTHOR]

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