Institut für Phytomedizin

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Bi‐directional hoeing in maize
(2023) Naruhn, Georg; Schneevoigt, Valentin; Hartung, Jens; Peteinatos, Gerassimos; Möller, Kurt; Gerhards, Roland
The weed control efficacy (WCE) of mechanical weeding in the inter‐row area in conventional cropping systems can achieve more than 90%. Despite the use of special intra‐row tools (e.g., finger weeders), only a WCE of 65%–75% can currently be realized in the intra‐row area. To close the gap between inter‐row and intra‐row WCE, in this study, a new approach for high‐efficacy precise mechanical weeding is presented. By using a GPS‐based pneumatic precision seeder (Kverneland GEOseed), a square crop seeding pattern of 37.5 cm × 37.5 cm was established in maize to enable post‐emergence hoeing lengthwise and transverse to the sowing direction. Thus, the treated area by the hoeing blades is postulated to increase, resulting in higher WCE. For this, six field experiments were conducted in South‐Western Germany in 2021 and 2022. Goosefoot blades and no‐till sweeps were guided automatically using a camera for row detection and a hydraulic side‐shift control for the hoe. This bi‐directional treatment was compared to an herbicide application and to hoeing treatments only along and transverse to the sowing direction. The bi‐directional hoeing treatment increased the WCE compared to hoeing along the crop rows on average from 80% to 95% and was not significantly different from the herbicide applications in 2022. Precise sowing in combination with hoeing along and transverse the crop rows resulted in 5.3% crop losses compared to 2.2% for hoeing only along the sowing direction by using only 15 cm wide goosefoot blades, while in the herbicide treatment and the untreated control no crop losses were detected. While maize biomass was not significantly different from the herbicide treatment in most cases over both years, in 2022, even the grain yield of the bi‐directional hoeing treatment with goosefoot blades (7.8 Mg ha−1) was statistically equal to the herbicide treatment (6.9 Mg ha−1). This study demonstrates the great potential of bi‐directional hoeing as an effective alternative to chemical weed control in row crops such as maize, sunflower and sugar beet.
A comparison of seven innovative robotic weeding systems and reference herbicide strategies in sugar beet (Beta vulgaris subsp. vulgaris L.) and rapeseed (Brassica napus L.)
(2023) Gerhards, Roland; Risser, Peter; Spaeth, Michael; Saile, Marcus; Peteinatos, Gerassimos
More than 40 weeding robots have become commercially available, with most restricted to use in crops or fallow applications. The machines differ in their sensor systems for navigation and weed/crop detection, weeding tools and degree of automation. We tested seven robotic weeding systems in sugar beet and winter oil‐seed rape in 2021 and 2022 at two locations in Southwestern Germany. Weed and crop density and working rate were measured. Robots were evaluated based on weed control efficacy (WCE), crop stand loss (CL), herbicide savings and treatment costs. All robots reduced weed density at least equal to the standard herbicide treatment. Band‐spraying and inter‐row hoeing with RTK‐GPS guidance achieved 75%–83% herbicide savings. When hoeing and band spraying were applied simultaneously in one pass, WCE was much lower (66%) compared to the same treatments in two separate passes with 95% WCE. Hoeing robots Farmdroid‐FD20®, Farming Revolution‐W4® and KULTi‐Select® (+finger weeder) controlled 92%–94% of the weeds. The integration of Amazone spot spraying® into the FD20 inter‐row and intra‐row hoeing system did not further increase WCE. All treatments caused less than 5% CL except for the W4‐robot with 40% CL and the combination of conventional inter‐row hoeing and harrowing (21% CL). KULT‐Vision Control® inter‐row hoeing with the automatic hydraulic side‐shift control resulted in 80% WCE with only 2% CL. Due to the low driving speed of maximum 1 km h−1 of hoeing robots with in‐row elements, treatment costs were high at 555–804 € ha−1 compared to camera‐guided inter‐row hoeing at 221 € ha−1 and broadcast herbicide application at 307–383 € ha−1. Even though the costs of robotic weed management are still high, this study shows that robotic weeding has become a robust, and effective weed control method with great potential to save herbicides in arable and vegetable crops.
Facilitation of weed seed predation by living mulch and cover crops
(2022) Schumacher, Matthias; Gerhards, Roland
Weed seed predation (WSP) is an important agro‐ecosystem service that naturally suppresses weed populations. Disturbances directly interfere with the activity of the seed predators, for example, harvest and soil tillage during a peak in weed seed availability (around cereal harvest). Plant soil cover and reduced soil tillage are factors that might positively affect WSP. We investigated cover crops and living mulch along with soil disturbance (no‐till and conventional seeding) in comparison to a fallow and repeated stubble tillage with a chisel plough in terms of WSP, activity‐density of carabid beetles and soil cover. A field experiment with a randomised complete block design and four replications was conducted at two sites from 2017 until 2019. WSP rates were assessed with seed cards and exclosure cages from July until November during a period of eight consecutive days each month. Living mulch exhibited the highest WSP rates of 72% with a maximum of 95% immediately following cereal harvest in August and September of 2017 and 2019, while the remainder of the treatments ranged from 2% to 5% WSP. In October and November mustard showed on average twice as high WSP rates compared to the other treatments (50% vs. 10%–25%). Seeding and soil tillage did not significantly influence carabid beetle activity‐density and WSP, except for living mulch. Predator groups (invertebrates and vertebrates) were not influenced by the various treatments, rather year and month determined the predator groups dominance. Besides their weed suppressive effects, living mulches and cover crops also facilitate WSP.

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