Browsing by Person "Naruhn, Georg-Peter"

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Efficacy of various mechanical weeding methods - single and in combination - in terms of different field conditions and weed densities
(2021) Naruhn, Georg-Peter; Peteinatos, Gerassimos G.; Butz, Andreas F.; Möller, Kurt; Gerhards, Roland
Public awareness and environmental policies have increased interest in applying non-herbicide weed control methods in conventional farming systems. Even though mechanical weed control has been used for centuries in agricultural practice, continuous developments—both in terms of implements and automation technologies—are continuously improving the potential outcomes. Current mechanical weed control methods were evaluated for their weed control efficacy and effects on yield potential against their equivalent herbicide methods. Furthermore, not much is known about the correlation between weed control efficacy (WCE) of different mechanical methods at varying weed density levels. A total of six experiments in winter wheat (2), peas (2), and soybean (2) were carried out in the years 2018, 2019, and 2020 in southwestern Germany. Harrowing and hoeing treatments at different speeds were carried out and compared to the herbicide treatments and untreated control plots. Regarding the average WCE, the combination of harrowing and hoeing was both the strongest (82%) and the most stable (74–100%) mechanical treatment in the different weed density levels. Whereas, in average, hoeing (72%) and harrowing (71%) were on the same WCE level, but harrowing (49–82%) was more stable than hoeing (40–99%). The grain yields in winter wheat varied between 4.1 Mg∙ha−1 (control) and 6.3 Mg∙ha−1 (harrow), in pea between 2.8 Mg∙ha−1 (hoe slow) and 5.7 Mg∙ha−1 (hoe fast) and in soybean between 1.7 Mg∙ha−1 (control) and 4 Mg∙ha−1 (herbicide). However, there were no significant differences in most cases. The results have shown that it is not possible to pinpoint a specific type of treatment as the most appropriate method for this cultivation, across all of the different circumstances. Different field and weather conditions can heavily affect and impact the expected outcome, giving, each time, an advantage for a specific type of treatment.
Non-chemical weed control in different cropping systems
(2025) Naruhn, Georg-Peter; Gerhards, Roland
Weeds are considered one of the major constraints in agriculture. The use of herbicides is the most common form of weed control so far. Therefore, herbicides account for approximately 60% of the agrochemicals applied worldwide. However, the raised public awareness of the environmental drawbacks as well as the risk of pesticide residues in the human food chain have increased the interest in non-chemical weed control methods also in conventional farming. Therefore, the importance of integrated weed management (IWM) with its preventive (e.g. crop rotation, row spacing, or crop plant distribution), and curative (mechanical or thermal methods) approaches is increasing. For reasons of cost efficiency, mechanical weed control (MWC) is currently the most important non-chemical procedure for direct weeding. Under optimal conditions, MWC can be as effective as a broadcast herbicide application. However, the strong variations in weed control efficacy (WCE) as well as crop/weed selective highly efficient intra-row weeding remain challenging for MWC. The aim of this work was to gain a better understanding of the variations in WCE of mechanical weeding and to advance non-chemical weed management by improving crop competitiveness and by enhancing the intra-row WCE. Therefore, the first section deals with factors that influence WCE with a special focus on site conditions and weed density. Harrowing and hoeing treatments were carried out in winter wheat, peas, and soybeans at three different sites. The mechanical treatments were examined regarding their WCE and yield effects and compared to a standard broadcast herbicide application and an untreated control. It was shown, that post-emergence harrowing and hoeing at the early growth stage of crops (BBCH 11-12) and weeds increased WCE by 18% compared to their application in later crop growth stages (BBCH 14-17). Therefore, it was concluded, that the timing of the treatment seems to have a stronger effect on WCE than pure site-related factors such as weed density at the time of application. Due to the different modes of action of harrowing and hoeing, it was assumed that combining them might close efficacy gaps and thus enhance WCE while simultaneously minimizing its variations. The high WCE against Alopecurus myosuroides as shown in the current study, is particularly important in terms of a sustainable weed resistance management, as it reduces the pressure on herbicide performance. Concerning the question of how the weed density affects the WCE of different methods of MWC, the results were inconclusive. When harrowing and hoeing were not combined, it was not possible to pinpoint a specific type of treatment as the most appropriate. Different field and weather conditions can heavily affect and impact the expected outcome, giving, each time, an advantage for a specific type of treatment. In the second section, weed management in an equal space seeding (ESS) system was investigated in maize, covering the two sub-aspects: I) weed suppression ability and crop development compared to a conventional row seeding (CRS) system, and II) enhancing WCE by bi-directional hoeing along and transverse to the sowing direction. Therefore, a square crop pattern was established by using a GPS-based pneumatic precision seeder. Leaf area index (LAI) and absorption rates of the photosynthetically active radiation (PAR) were calculated. ESS and CRS were then compared regarding weed suppression and crop development. Additionally, in the ESS system post-emergence hoeing treatments along and transverse to the sowing direction, one way and in both directions were carried out and compared to a standard herbicide application and an untreated control. WCE, crop losses, weed, and crop biomass as well as crop yield were investigated. It was found that ESS did not affect the weed suppression ability of maize crops. Compared to CRS, the crops in ESS neither built a higher LAI nor absorbed more PAR. However, the ESS showed significantly higher grain yields than the CRS. Due to the very dry weather conditions in 2022, it was assumed, that dry soil conditions reduced the potential of the maize plants competitive advantage over weeds. The yield advantage of ESS over CRS, rather appears to be explained by a lower intra-specific competition due to an optimized crop plant arrangement, side effects on root growth, or side effects of hoeing for example on water availability or better nutrient uptake from the soil. Apart from the preventive weeding approach of ESS, bi-directional hoeing along and transverse to the sowing direction increased WCE compared to hoeing along the crop rows on average from 80% to 95%. In 2022 the bi-directional hoeing treatment was statistically equal to the herbicide application (98%) without causing higher crop losses (5%) than when using special intra-row weeding tools (e.g. finger or torsion weeders). Although not statistically different in most cases, the bi-directional hoeing treatments achieved the highest grain yield and showed no water stress compared to all other treatments. Therefore, it was assumed that hoeing could reduce soil water evaporation by breaking the soil capillaries, resulting in improved water retention and ultimately higher grain yields. Assuming, IWM provides generally the most promising approach, findings of this thesis show the potential and the importance of precision farming technologies for future agriculture. Especially in terms of climate-resilient cropping systems, where highly efficient crop/weed selective non-chemical direct weed control can be applied, the results of the higher grain yields of ESS compared to CRS as well as the increased WCE of bi-directional hoeing should be given greater consideration in practical farming.